Ansys Turbogrid

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ANSYS TurboGrid Tutorials

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Table of Contents1. Introduction to the ANSYS TurboGrid Tutorials ................................................................................................. 1

Preparing a Working Directory ........................................................................................................... 1Setting the Working Directory and Starting ANSYS TurboGrid ................................................................ 1Changing the Display Colors ............................................................................................................. 1Editor Buttons ................................................................................................................................. 2Using Help ..................................................................................................................................... 2

2. Rotor 37 ..................................................................................................................................................... 3Overview of the Mesh Creation Process ............................................................................................... 4Before You Begin ............................................................................................................................ 4Starting ANSYS TurboGrid ............................................................................................................... 4Defining the Geometry ..................................................................................................................... 5Defining the Topology ...................................................................................................................... 6Reviewing the Mesh Data Settings ...................................................................................................... 8Reviewing the Mesh Quality on the Hub and Shroud Tip Layers ............................................................... 8Adding Intermediate Layers ............................................................................................................... 9Generating the Mesh ........................................................................................................................ 9Analyzing the Coarse Mesh ............................................................................................................. 10Analyzing the Coarse Mesh Quality ................................................................................................... 10Looking at Mesh Data Values ........................................................................................................... 11Visualizing the Hub-to-Shroud Element Distribution ............................................................................. 11Increasing the Mesh Density ............................................................................................................ 12Regenerating the Mesh .................................................................................................................... 13Analyzing the Fine Mesh ................................................................................................................. 13Analyzing the Fine Mesh Quality ...................................................................................................... 13Visualizing the Hub-to-Shroud Element Distribution in the Fine Mesh ..................................................... 14Observing the Shroud Tip Mesh ........................................................................................................ 15Examining the Mesh Qualitatively ..................................................................................................... 16Creating a Legend .......................................................................................................................... 17Saving the Mesh ............................................................................................................................ 17Saving the State (Optional) .............................................................................................................. 17

3. Steam Stator .............................................................................................................................................. 19Before You Begin ........................................................................................................................... 20Starting ANSYS TurboGrid ............................................................................................................. 20Defining the Geometry .................................................................................................................... 20Loading the Curves ........................................................................................................................ 20Modifying the Curve Type ............................................................................................................... 22Defining the Topology .................................................................................................................... 23Reviewing the Mesh Data Settings .................................................................................................... 23Reviewing the Mesh Quality on the Hub and Shroud Layers ................................................................... 23Modifying the Hub and Shroud Layers ............................................................................................... 24Generating the Mesh ....................................................................................................................... 25Analyzing the Mesh ....................................................................................................................... 25Examining the Mesh Qualitatively ..................................................................................................... 26Saving the Mesh ............................................................................................................................ 27Saving the State (Optional) .............................................................................................................. 27

4. Radial Compressor ...................................................................................................................................... 29Before You Begin ........................................................................................................................... 30Starting ANSYS TurboGrid ............................................................................................................. 30Defining the Geometry .................................................................................................................... 30Defining the Machine Data .............................................................................................................. 31Defining the Hub ........................................................................................................................... 31Defining the Shroud ....................................................................................................................... 31Defining the Blade ......................................................................................................................... 32Defining the Topology .................................................................................................................... 33Reviewing the Mesh Data Settings .................................................................................................... 34

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Reviewing the Mesh Quality on the Hub and Shroud Layers ................................................................... 34Modifying the Hub Layer ................................................................................................................ 34Generating the Mesh ....................................................................................................................... 36Analyzing the Mesh ....................................................................................................................... 36Saving the Mesh ............................................................................................................................ 37Saving the State (Optional) .............................................................................................................. 37

5. Axial Fan .................................................................................................................................................. 39Before You Begin ........................................................................................................................... 40Starting ANSYS TurboGrid ............................................................................................................. 40Defining the Geometry .................................................................................................................... 40Defining the Topology .................................................................................................................... 42Reviewing the Mesh Data Settings .................................................................................................... 43Reviewing the Mesh Quality on the Hub and Shroud Tip Layers ............................................................. 43Modifying the Shroud Tip Layer ....................................................................................................... 43Generating the Mesh ....................................................................................................................... 44Analyzing the Mesh ....................................................................................................................... 44Adding Inlet and Outlet Domains ...................................................................................................... 45Regenerating the Mesh .................................................................................................................... 45Analyzing the New Mesh ................................................................................................................ 45Saving the Mesh ............................................................................................................................ 45Saving the State (Optional) .............................................................................................................. 46

6. Splitter Blades ........................................................................................................................................... 47Before You Begin ........................................................................................................................... 48Starting ANSYS TurboGrid ............................................................................................................. 48Defining the Geometry .................................................................................................................... 48Defining the Topology .................................................................................................................... 49Reviewing the Topology Settings ...................................................................................................... 49Reviewing the Mesh Data Settings .................................................................................................... 49Reviewing the Mesh Quality on the Hub and Shroud Layers ................................................................... 49Modifying the Hub Layer ................................................................................................................ 49Generating the Mesh ....................................................................................................................... 50Analyzing the Mesh ....................................................................................................................... 51Saving the Mesh ............................................................................................................................ 51Saving the State (Optional) .............................................................................................................. 51

7. Tandem Vane ............................................................................................................................................. 53Before You Begin ........................................................................................................................... 54Starting ANSYS TurboGrid ............................................................................................................. 54Defining the Geometry .................................................................................................................... 55Defining the Topology .................................................................................................................... 55Reviewing the Topology Settings ...................................................................................................... 55Reviewing the Mesh Data Settings .................................................................................................... 56Reviewing the Mesh Quality on the Hub and Shroud Layers ................................................................... 56Modifying the Hub Layer ................................................................................................................ 56Modifying the Shroud Tip Layer ....................................................................................................... 59Increasing the Mesh Density ............................................................................................................ 59Further Modifying the Hub Layer ...................................................................................................... 60Generating the Mesh ....................................................................................................................... 62Saving the Mesh ............................................................................................................................ 62Saving the State (Optional) .............................................................................................................. 62

8. Batch Mode Studies .................................................................................................................................... 65Before You Begin ........................................................................................................................... 65Part 1: Parametric Study .................................................................................................................. 65Starting ANSYS TurboGrid ............................................................................................................. 65Defining the Geometry .................................................................................................................... 65Creating the Topology and Modifying the Mesh ................................................................................... 66Creating the Session File ................................................................................................................. 66Running the Session File ................................................................................................................. 67Part 2: Grid Refinement .................................................................................................................. 68

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ANSYS TurboGrid Tutorials

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Starting ANSYS TurboGrid ............................................................................................................. 68Defining the Geometry and Topology ................................................................................................ 68Creating the Session File ................................................................................................................. 69Running the Session File ................................................................................................................. 70

9. Deformed Turbine ...................................................................................................................................... 73Before You Begin ........................................................................................................................... 74Starting ANSYS TurboGrid ............................................................................................................. 74Mesh for the Deformed Blade Group ................................................................................................. 74Defining the Geometry for the Deformed Blade Group .......................................................................... 74Defining the Topology for the Deformed Blade Group .......................................................................... 79Reviewing the Mesh Data Settings for the Deformed Blade Group .......................................................... 80Reviewing the Mesh Quality on the Hub and Shroud Tip Layers of the Deformed Blade Group .................... 80Increasing the Mesh Density for the Deformed Blade Group .................................................................. 84Revisiting the Mesh Quality on the Hub and Shroud Tip Layers of the Deformed Blade Group ..................... 86Generating the Mesh for the Deformed Blade Group ............................................................................. 86Analyzing the Mesh for the Deformed Blade Group .............................................................................. 86Saving the Mesh for the Deformed Blade Group .................................................................................. 86Saving the State for the Deformed Blade Group (Optional) .................................................................... 86Mesh for an Undeformed Blade ........................................................................................................ 87Starting a New Case ....................................................................................................................... 87Defining the Geometry for the Undeformed Blade ................................................................................ 87Defining the Topology for the Undeformed Blade ................................................................................ 88Reviewing the Mesh Data Settings for the Undeformed Blade ................................................................ 89Reviewing the Mesh Quality on the Hub and Shroud Tip Layers of the Undeformed Blade .......................... 89Increasing the Mesh Density for the Undeformed Blade ........................................................................ 90Revisiting the Mesh Quality on the Hub and Shroud Tip Layers of the Undeformed Blade ........................... 91Generating the Mesh for the Undeformed Blade ................................................................................... 91Analyzing the Mesh for the Undeformed Blade .................................................................................... 91Saving the Mesh for the Undeformed Blade ........................................................................................ 91Saving the State for the Undeformed Blade (Optional) .......................................................................... 92Summary ...................................................................................................................................... 92Further Exercise ............................................................................................................................ 92

10. Francis Turbine ......................................................................................................................................... 93Before You Begin ........................................................................................................................... 94Starting ANSYS TurboGrid ............................................................................................................. 94Defining the Geometry .................................................................................................................... 94Adjusting the Outlet Points .............................................................................................................. 95Defining the Topology .................................................................................................................... 96Reviewing the Mesh Quality on the Hub and Shroud Layers ................................................................... 97Modifying the Hub Layer ................................................................................................................ 97Modifying the Shroud Layer ........................................................................................................... 100Specifying Mesh Data Settings ....................................................................................................... 101Generating the Mesh ..................................................................................................................... 102Analyzing the Mesh ...................................................................................................................... 102Saving the Mesh .......................................................................................................................... 103Saving the State (Optional) ............................................................................................................. 103

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ANSYS TurboGrid Tutorials

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List of Figures2.1. J-Grid Topology and 2D Mesh on the Hub ...................................................................................................... 82.2. Hub-to-Shroud Element Distribution ............................................................................................................ 122.3. Hub-to-Shroud Element Distribution in the Fine Mesh .................................................................................... 152.4. Surface Group: Tip Near Leading Edge ........................................................................................................ 153.1. Incorrect Hub and Shroud Representations .................................................................................................... 223.2. Modification near Shroud Trailing Edge ....................................................................................................... 244.1. Hub and Shroud of Radial Compressor ......................................................................................................... 324.2. Master Control Point Adjusted Near Hub Leading Edge ................................................................................... 354.3. Added Master Control Point Adjusted Near Hub O-Grid .................................................................................. 365.1. Effect of Moving Passage Outlet Towards Blade ............................................................................................ 425.2. Master Control Points Adjusted on Shroud Tip Layer ...................................................................................... 446.1. Master Control Point Adjusted Near Hub Leading Edge ................................................................................... 507.1. Moving a Control Point on the Hub Layer ..................................................................................................... 577.2. Inserting and Moving a Control Point on the Hub Layer .................................................................................. 587.3. Inserting and Moving Another Control Point on the Hub Layer ......................................................................... 597.4. Poor Face Angles ..................................................................................................................................... 607.5. Making Control Points “Sticky” .................................................................................................................. 617.6. Adding and Moving Control Points .............................................................................................................. 629.1. Blade Set Containing a Deformed Blade ....................................................................................................... 769.2. Adjusting the Inlet Points ........................................................................................................................... 779.3. Adjusting the Outlet Points ........................................................................................................................ 789.4. Hub Layer Changes .................................................................................................................................. 819.5. Shroud Tip Layer Changes - Control Point Movements .................................................................................... 829.6. Shroud Tip Layer Changes - New Control Point ............................................................................................. 839.7. Shroud Tip Layer Changes - A Second New Control Point ............................................................................... 849.8. Hub Layer Changes .................................................................................................................................. 9010.1. Hub Layer Changes in Downstream End ..................................................................................................... 9810.2. Hub Layer Changes in Upstream End ......................................................................................................... 9910.3. Increasing Mesh Density Locally ............................................................................................................. 10010.4. Shroud Layer Changes ........................................................................................................................... 101

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Chapter 1. Introduction to the ANSYSTurboGrid Tutorials

The ANSYS TurboGrid tutorials are designed to introduce general mesh-generation techniques used in ANSYSTurboGrid.

NoteThese tutorials assume that you are using ANSYS TurboGrid in Standalone mode. If you would like toattempt running one of these tutorials in ANSYS Workbench, you should first be familiar with ANSYSWorkbench and review the documentation in ANSYS TurboGrid in ANSYS Workbench (p. 9) in theANSYS TurboGrid Introduction.

You should review the following topics before attempting to start a tutorial for the first time:

• Preparing a Working Directory (p. 1)

• Setting the Working Directory and Starting ANSYS TurboGrid (p. 1)

• Changing the Display Colors (p. 1)

• Editor Buttons (p. 2)

• Using Help (p. 2)

Preparing a Working DirectoryANSYS TurboGrid uses a working directory as the default location for loading and saving files for a particularsession or project. Before you run a tutorial, you must create a working directory and copy in the files that are listednear the top of the tutorial. These files are located in <CFXROOT>/examples, where <CFXROOT> is the installationdirectory for ANSYS TurboGrid.

By working in a new directory, you prevent accidental changes to any of the files that came with your installation.

Setting the Working Directory and Starting ANSYSTurboGrid

Before you start ANSYS TurboGrid, set the working directory.

1. Start the CFX launcher.

For details, see Starting the CFX Launcher (p. 7) in the ANSYS TurboGrid Introduction.

2. Select a working directory.

3. Click the TurboGrid 12.1 button.

Changing the Display ColorsIf viewing objects in ANSYS TurboGrid becomes difficult due to contrast with the background, the colors can bealtered for improved viewing. The color options are set in different places, depending on how you run ANSYSTurboGrid, as follows:

1. Select Edit > Options.

The Options dialog box appears.

2. Adjust the color settings under TurboGrid > Viewer.

3. Click OK.

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Editor ButtonsThe ANSYS TurboGrid interface uses editors to enter the data required to create a mesh. The editors have standardbuttons, which are described next:

• Apply applies the information contained within all the tabs of an editor.

• OK is the same as Apply, except that the editor automatically closes.

• Cancel and Close both close the editor without applying or saving any changes.

• Reset returns the settings for the object to those stored in the database for all the tabs. The settings are storedin the database each time the Apply button is clicked.

• Defaults restores the system default settings for all the tabs of the edited object.

Using HelpTo invoke the help browser, select Help > Master Contents.

You may also try using context-sensitive help. Context-sensitive help is provided for many of the object editorsand other parts of the interface. To invoke the context-sensitive help for a particular editor or other feature, ensurethat the feature is active, place the mouse pointer over it, then press F1. Not every area of the interface supportscontext-sensitive help. If context-sensitive help is not available for the feature of interest, select Help > MasterContents and try using the search or index features in the help browser.

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Editor Buttons

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Chapter 2. Rotor 37This tutorial includes:

• Overview of the Mesh Creation Process (p. 4)

• Before You Begin (p. 4)

• Starting ANSYS TurboGrid (p. 4)

• Defining the Geometry (p. 5)

• Defining the Topology (p. 6)

• Reviewing the Mesh Data Settings (p. 8)

• Reviewing the Mesh Quality on the Hub and Shroud Tip Layers (p. 8)

• Adding Intermediate Layers (p. 9)

• Generating the Mesh (p. 9)

• Analyzing the Coarse Mesh (p. 10)

• Increasing the Mesh Density (p. 12)

• Regenerating the Mesh (p. 13)

• Analyzing the Fine Mesh (p. 13)

• Saving the Mesh (p. 17)

• Saving the State (Optional) (p. 17)

This tutorial demonstrates the basic workflow for generating a CFD mesh using ANSYS TurboGrid. As you workthrough this tutorial, you will create a mesh for a blade passage of an axial compressor blade row. A typical bladepassage is shown by the black outline in the figure below.

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The blade row contains 36 blades that revolve about the negative Z-axis. A clearance gap exists between the bladesand the shroud, with a width of 2.5% of the total span. Within the blade passage, the maximum diameter of theshroud is approximately 51 cm.

After creating the mesh with the default mesh density, you will check the mesh quality. You will then increase themesh density and regenerate the mesh. Finally, you will save the mesh in a format that can be used by ANSYS CFXin a CFD simulation.

Overview of the Mesh Creation ProcessBefore ANSYS TurboGrid can create a mesh, you must provide it with several pieces of information. Such informationincludes the location of the geometry files (hub, shroud, and blades), the mesh topology type, and the distributionof mesh nodes. All of the data that you provide is stored in a set of data objects known as CCL objects. After youhave specified the CCL objects appropriately, you can issue a command for ANSYS TurboGrid to generate a mesh.

The ANSYS TurboGrid user interface organizes the CCL objects in a tree view known as the object selector. Youcan use the object selector to select and edit the CCL objects; the objects are listed from top to bottom in the standardorder for creating a mesh. The user interface also has a toolbar for selecting and editing the CCL objects; the iconsare arranged from left to right in the standard order for creating a mesh.

Regardless of whether you use the object selector or the toolbar, you should generally follow this sequence whencreating a mesh:

1. Define the geometry by loading files and changing settings as required.

2. Define the topology by choosing a topology type and optionally changing other topology settings.

3. Optionally modify the Mesh Data settings that govern the number and the distribution of nodes in variousparts of the mesh.

If you plan to make a fine (high-resolution) mesh, you can optionally set the mesh density at a later time inorder to minimize processing time while establishing the topology. Keep in mind that changing the meshdensity can affect the mesh quality.

4. Improve the topology on the hub and shroud layers as required.

5. Optionally add intermediate 2D layers that guide the 3D topology and mesh. If you do not add layers at thispoint, they will be added as required when you generate the mesh. Adding them early gives you a chance tocheck and adjust the 2D mesh quality on the intermediate layers before generating the full 3D mesh.

6. Issue the command to generate a mesh.

7. Check the mesh quality. As required, adjust the topology type and distribution, and Mesh Data settings. Ifyou make changes, go back to the previous step.

8. Save the mesh to a file.

Before You BeginBefore you begin this tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/rotor37 directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

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Overview of the Mesh Creation Process

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Defining the GeometryThe provided geometry files, which consist of a BladeGen.inf file plus three curve files, were created usingBladeGen. To load the information contained in those files, you will load the BladeGen.inf file. ANSYSTurboGrid uses this file to set the axis of rotation, the number of blades, and a length unit that characterizes thescale of the machine. It also uses this file to identify the curve files which it then loads to define the curvature ofthe hub, shroud, and a single blade. The geometric data from the input files is processed to generate a geometricrepresentation, an outline of which appears in the viewer.

After the geometry has been generated, you are invited to browse through the objects created under the Geometryobject in the object selector.

Initially, the blades extend from the hub to the shroud. After inspecting the geometry, you will create the requiredgap between the blade and the shroud.

Load the BladeGen.inf file:

1. Click File > Load BladeGen.

2. Open BladeGen.inf from the working directory.

The progress bar at the bottom right of the screen shows the geometry generation progress. After the geometryhas been generated, you can see the hub, shroud, and blade for one passage. Along the blade, you can see theleading and trailing edge curves (green and red lines, respectively). An outline drawing (the Outline object)traces the 3D space that is available for meshing; the latter consists of an inlet domain, passage, and outletdomain. In this tutorial, you will generate a mesh for the passage only.

NoteIt is possible to adjust the upstream and downstream extents of the hub and shroud surfaces (bychanging the Inlet and Outlet geometry objects). It is also possible to create an extended meshthat includes the inlet and outlet domains (by editing the Mesh Data settings).

Examine the geometry:

1. To understand the correlation between the geometry objects listed in the object selector and the locations inthe geometry, toggle the visibility check box next to each object in the object selector and observe the changein the viewer. In order to avoid cluttering the view, ensure that only the Hub, Shroud, Blade 1, andOutline objects have visibility turned on before continuing to the next step.

2. Open Geometry > Machine Data from the object selector by double-clicking Machine Data in theobject selector, or by right-clicking Machine Data and selecting Edit from the shortcut menu that appears.

Here you can see basic information about the geometry. Note that the units specified for Base Units representthe scale of the geometry being meshed; these units are not used for importing geometric data nor do theygovern the units written to a mesh file; they are used for the internal representation of the geometry to minimizecomputer round-off errors.

3. Open Geometry > Hub.

Here you can see information about which file was used for hub data and how the file was interpreted. Similarinformation can be seen by opening the Shroud and Blade 1 objects. Note that, for the Hub and Shroudobjects, the Curve Type parameter is set to Piece-wise linear; this is a result of loading aBladeGen.inf file.

4. Click Display all blade instances to obtain a view of the entire geometry.

5. Click Display single blade instance to show a single blade instance once again.

To complete the geometry, create a small gap between the blade and the shroud. The blade should be shortened to97.5% of its original span because the gap width, as specified in the problem description, is 2.5% of the total span.

1. Open Geometry > Blade Set > Shroud Tip.

2. Set Tip Option to Constant Span.

3. Set Span to 0.975.

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Defining the Geometry

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4. Click Apply.

The names of the objects in the Geometry branch of the object selector are shown in black non-italic text, indicatingthat the Geometry objects are all defined. This completes the geometry definition.

Defining the TopologyNow that the geometry is defined, the next step is to create the topology that guides the mesh.

1. Open Topology Set.

2. Set Topology Definition > Placement to Traditional with Control Points.

This provides access to the officially supported topology methods. The other option, ATM Optimized(Beta), provides access to a Beta (unsupported) feature.

3. Set Topology Definition > Method to J-Grid.

Normally, you would choose the H/J/C/L-Grid method for the first attempt at a mesh, then change themethod if required. In this case, it was found that the J-Grid method produces a higher-quality mesh thanthe H/J/C/L-Grid method. The H/J/C/L-Grid method causes ANSYS TurboGrid to choose an H-Grid,J-Grid, C-Grid, L-Grid, or a combination of these, based on heuristics. In this case, the H/J/C/L-Gridmethod causes ANSYS TurboGrid to choose a J-Grid topology for the upstream end of the passage, and anH-Grid topology for the downstream end. Due to the high blade metal angle on the trailing edge near the shroud,the J-Grid topology is more appropriate for the downstream end. For details on the H/J/C/L-Grid method,see H/J/C/L Topology Definition (p. 82) in the ANSYS TurboGrid User's Guide.

4. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

5. Leave Include O-Grid > Width Factor set to 0.5.

This makes the O-Grid thickness equal to half the average blade thickness. In general, a suitable value of theO-Grid thickness depends on the blade geometry, topology type, and mesh density. Trial-and-error adjustmentsare sometimes required to establish a good value when creating the first mesh for a particular blade.

6. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

7. Click Apply.

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Defining the Topology

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8. Right-click Topology Set and turn off Suspend Object Updates.

The Topology Set object name in the object selector changes to black non-italic text, indicating that thisobject is now fully specified and has been generated.

After a short time, the topology appears on the hub and shroud as a structure of thick lines. Thinner lines showa preview of the mesh elements.

Object updates are suspended by default. To save computational time, you should generally keep object updatessuspended until you have finished defining the geometry. You must re-enable object updates and allow thetopology to be generated before freezing the topology settings, which is the next step.

9. Click Freeze.

It is recommended that you freeze the topology after you specify and generate it. This prevents the settings onthe Advanced Parameters tab of Topology Set > Blade 1 from inadvertently changing. Without freezingthe topology, unwanted changes to the topology block counts might occur as a result of making small adjustmentsto the topology (for example, moving a control point).

Estimates of the total number of nodes and elements are displayed at the bottom left of the screen. These estimatesare based on the default Mesh Data settings.

Change the view to clearly show the topology on the hub:

1. Click Hide all geometry objects .

2. Turn off the visibility of Layers > Shroud Tip to hide the topology on the shroud tip.

3. Right-click a blank area in the viewer, and click Predefined Camera > View Towards +X from the shortcutmenu.

The heavy lines in Figure 2.1, “J-Grid Topology and 2D Mesh on the Hub” (p. 8) indicate the (master) topologylines; the thinner lines show the 2D mesh for the hub. Note that the 3D mesh does not yet exist.

The mesh wraps around the blade at the leading and trailing edges. This is the main characteristic of the J-Gridtopology.

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Defining the Topology

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Figure 2.1. J-Grid Topology and 2D Mesh on the Hub

This completes the topology definition.

Reviewing the Mesh Data SettingsThe Mesh Data settings control the number and distribution of mesh elements. Open the Mesh Data objectand review the settings, but leave them at their default values. Note that the target number of nodes is set to producea coarse mesh. In the status bar in the bottom-left corner of ANSYS TurboGrid, you can see that the number ofmesh nodes is on the order of 40000.

As stated in the problem description for this tutorial, you will produce an initial coarse mesh and then, after verifyingthe mesh quality, you will increase the mesh density to produce a fine mesh. Leaving the mesh density coarse inthe meantime will reduce processing time while you adjust the topology.

Reviewing the Mesh Quality on the Hub and ShroudTip Layers

Layers are constant-span surfaces that are used for displaying and editing the topology, and for displaying a previewof the refined mesh. You have already seen the hub layer in Figure 2.1, “J-Grid Topology and 2D Mesh on theHub” (p. 8). At this point, there are two layers: Layers > Hub, and Layers > Shroud Tip.

Before generating the 3D mesh, it is recommended that you check the mesh quality on the layers, especially thehub and shroud tip layers. By correcting any mesh problems early, you can save time by minimizing the numberof times you generate the full 3D mesh.

If the topology were grossly skewed or distorted on the hub or shroud tip layer, the Layers object would be shownwith red text in the object selector. Since the Layers object is shown in black text, the mesh contains no regionswith high skew on the hub and shroud tip layers.

For a more detailed analysis of the mesh quality on a layer, open the layer object and read the list of mesh measures.If the mesh measures are not shown, select Refined Mesh Visibility and click Apply. The mesh measures showthe extreme values for the mesh elements. If any of the mesh measures are considered “bad”, they are listed in redtext. The criteria for “bad” mesh elements are set in the Mesh Analysis > Mesh Limits object. You candouble-click a red mesh measure to color the “bad” mesh elements red in the viewer.

In this case, elements with a very high aspect ratio exist close to the blade. This is to be expected, especially for acoarse mesh.

NoteThe quality criterion for the Maximum Aspect Ratio mesh measure is controlled by the Edge LengthRatio setting in the Mesh Analysis > Mesh Limits object.

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Adding Intermediate LayersANSYS TurboGrid can add layers as required in order to capture spanwise variations in the geometry. This processhappens when you generate a mesh, but can also be initiated manually, as demonstrated next:

1. Turn on the visibility of Layers > Shroud Tip to show the shroud layer, then right-click in the viewerand click Predefined Camera > Isometric View (Y up).

By viewing the hub and shroud layers from this angle, you can see where the new layers are added.

2. Open Layers.

Note that the message indicates that 1 layer will be added.

3. Click Auto Add Layers .

ANSYS TurboGrid adds additional layers as required; in this case, 1 layer is added.

4. Turn on the visibility of Layers > Layer 1 to see the new layer in the viewer.

5. To check the mesh quality on the new layer, open Layers > Layer 1, select Refined Mesh Visibility, andclick Apply.

Note that the face angles are acceptable on the new layer.

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

After the mesh has been generated, 3D mesh measures are available. You will check these in the next section. Meshvisualization objects, listed under 3D Mesh, are also available. By default, one of these objects, called ShowMesh, is shown in the viewer. You can alter this object or view other 3D Mesh objects to inspect different partsof the mesh. Later in this tutorial, you will view some of the objects listed under 3D Mesh.

• Before proceeding to the next section, turn off the visibility of 3D Mesh > Show Mesh so that you can seethe mesh without obstruction.

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The mesh is relatively coarse. Such a mesh is suitable when you need to regenerate the mesh repeatedly in the courseof improving the mesh quality. After attaining the required level of mesh quality, you should make a finer mesh.Later in this tutorial, you will generate a finer mesh.

NoteIn some cases, the mesh quality can be adversely affected by increasing the mesh density, making furtheradjustments necessary.

Analyzing the Coarse MeshThis section includes:

• Analyzing the Coarse Mesh Quality (p. 10)

• Looking at Mesh Data Values (p. 11)

• Visualizing the Hub-to-Shroud Element Distribution (p. 11)

Analyzing the Coarse Mesh QualityNow that the mesh has been generated, 3D mesh measures are available. These are analogous to the 2D meshmeasures that are calculated on layers. As for the 2D mesh measures, the 3D mesh measures have quality criteriaset in the Mesh Analysis > Mesh Limits object.

When any mesh measure fails to meet the criteria, Mesh Analysis > Mesh Statistics (Error) willappear in red text in the object selector. With default criteria, there will almost always be some mesh elements thatfall outside the criteria; a visual inspection of the mesh measures is usually required to determine whether the meshis satisfactory.

Check the 3D mesh statistics:

1. For a visual frame of reference, ensure that Layers > Hub and Layers > Shroud Tip are visible.

2. Open Mesh Analysis or Mesh Analysis > Mesh Statistics.

The mesh statistics shown here may differ slightly from what you see:

In this case, Maximum Element Volume Ratio and Maximum Edge Length Ratio do not meetthe criteria. Not all of the mesh statistics carry the same importance. For example, it is necessary to have amesh with no negative volumes. Generally, poor angles should also be fixed, but Maximum Edge LengthRatio and Maximum Element Volume Ratio values should be judged based on your requirements.

3. Double-click Maximum Element Volume Ratio to display the elements that have an element volumeratio greater than 2 (the default criterion). Alternatively, you can select Maximum Element VolumeRatio and then click Display.

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A built-in volume object, Mesh Analysis > Show Limits, automatically changes its definition andappears in the viewer. This volume object includes the mesh elements that fail to meet the criteria for theselected mesh measure.

The volume object appears mainly on the blade, hub, and shroud surfaces. This is normal. Note that part ofthe mesh upstream and downstream of the blade is also included in the volume object. To improve the elementvolume ratio in these regions, you will increase the mesh density later in this tutorial.

4. Double-click Maximum Edge Length Ratio to display the elements that have an edge length ratiogreater than 100 (the default criterion).

The Mesh Analysis > Show Limits object appears mainly on the blade, hub and shroud surfaces. Thisis normal.

5. Click Close.

6. Turn off the visibility of Mesh Analysis > Show Limits.

Looking at Mesh Data ValuesThe Mesh Data editor tabs can be used to set and display information about the mesh. In the following steps, youwill examine the number and distribution of elements from hub to shroud tip and from shroud tip to shroud.

1. Open Mesh Data.

2. Click the Passage tab.

Look in the Spanwise Blade Distribution Parameters section. Method is set to End Ratio with a valueof 200. The other boxes in the section are grayed out, but show the current value for each option that ANSYSTurboGrid has calculated.

You can see that # of Elements is 20. This will change when you refine the mesh later in this tutorial.

3. Click the Shroud Tip tab.

Look in the Shroud Tip Distribution Parameters section. Method is set to Match Expansion atBlade Tip. You can see that the number of elements from shroud tip to shroud is 11.

Visualizing the Hub-to-Shroud Element DistributionTo demonstrate the use of the 3D Mesh visualization objects, and for comparison with the finer mesh that you willmake later in this tutorial, look at the mesh distribution from hub to shroud as follows:

1. Click Unhide geometry objects .

2. Turn off the visibility of the following objects:

• Geometry > Blade Set > Blade 1

• Layers > Hub

• Layers > Layer 1

• Layers > Shroud Tip

• 3D Mesh > Show Mesh

3. Turn on the visibility of the following objects:

• 3D Mesh > LOWBLADE

• 3D Mesh > HIGHPERIODIC.

4. Observe the element distribution from hub to shroud tip and from shroud tip to shroud.

See Figure 2.2, “Hub-to-Shroud Element Distribution” (p. 12).

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Figure 2.2. Hub-to-Shroud Element Distribution

Increasing the Mesh DensityAs mentioned at the beginning of this tutorial, you will increase the mesh density. Such an increase in mesh densitycan result in a more accurate CFD solution.

1. Open Mesh Data.

2. On the Mesh Size tab, leave Method set to Target Passage Mesh Size.

3. Set Node Count to Fine (250000).

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4. Click Apply.

Regenerating the MeshAfter changing the mesh density, the coarse mesh was deleted. Generate the fine mesh:

• Click Insert > Mesh.

Analyzing the Fine MeshThis section includes:

• Analyzing the Fine Mesh Quality (p. 13)

• Visualizing the Hub-to-Shroud Element Distribution in the Fine Mesh (p. 14)

• Observing the Shroud Tip Mesh (p. 15)

• Examining the Mesh Qualitatively (p. 16)

• Creating a Legend (p. 17)

Analyzing the Fine Mesh QualityChanging the mesh density can affect the mesh statistics. Confirm that the mesh statistics are acceptable:

1. Open Mesh Analysis.

The mesh statistics shown here may differ slightly from what you see:

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You can see that, in this case, after increasing the mesh density, the Maximum Element Volume Ratiomesh statistic has improved.

2. Double-click Maximum Element Volume Ratio.

Note that the volume object does not occupy as much of the mesh upstream and downstream of the blade asit did for the coarse mesh. The element volume ratio in these regions has improved as a result of increasingthe mesh density.

3. Click Close.

4. Turn off the visibility of Mesh Analysis (Error) > Show Limits.

Visualizing the Hub-to-Shroud Element Distribution in the FineMesh

Now that the mesh density has been increased, re-examine the spanwise distribution of mesh elements:

1. On the Passage tab for the Mesh Data object, compare the number of elements from hub to shroud tip (66)with the value obtained for the coarse mesh (20). The number of elements has risen.

2. Look at the Shroud Tip tab to verify that more elements now exist between the shroud tip and shroud (11before, now 16).

3. See Figure 2.3, “Hub-to-Shroud Element Distribution in the Fine Mesh” (p. 15), and compare it with Figure 2.2,“Hub-to-Shroud Element Distribution” (p. 12).

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Figure 2.3. Hub-to-Shroud Element Distribution in the Fine Mesh

4. Turn off the visibility of all of the 3D Mesh objects.

Observing the Shroud Tip MeshA mesh interface exists in the shroud tip gap. In order to see this interface:

1. Turn on the visibility of 3D Mesh > SHROUD TIP.

2. Click Hide all geometry objects .

3. Zoom in to view the mesh on the shroud tip.

Figure 2.4, “Surface Group: Tip Near Leading Edge” (p. 15) shows this mesh at the leading edge of the blade.Note how the nodes do not line up along the middle of the blade, due to the default use of a general grid (GGI)interface along the shroud tip of the blade.

Figure 2.4. Surface Group: Tip Near Leading Edge

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Observing the Shroud Tip Mesh

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4. Turn off the visibility of 3D Mesh > SHROUD TIP.

5. Click Unhide geometry objects .

Examining the Mesh QualitativelyYou will now examine the mesh qualitatively using a turbo surface. Change the Show Mesh turbo surface so thatit appears on the hub, and color it to show the variation in Edge Length Ratio (a variable that was computedat the time the mesh was generated):

1. Turn on the visibility of 3D Mesh > Show Mesh.

2. Open 3D Mesh > Show Mesh.

3. Leave Variable set to K.

K is equal to the node number in the spanwise direction, ranging from 1 at the hub to a positive integer valueat the shroud.

4. Set Value to 1.

This will cause the turbo surface to appear on the hub.

5. Click the Color tab.

6. Ensure that Mode is set to Variable.

7. Set Variable to Edge Length Ratio.

8. Set Range to Local.

This will cause the range of colors in the color map to be distributed over the range of values found on theturbo surface, rather that over the global range or a user-defined range.

9. Click the Render tab.

10. Ensure that Draw Faces is selected.

11. Click Apply.

12. To avoid visual conflicts between the turbo surface and the hub, which are coincident, turn off the visibilityof Geometry > Hub.

Note that you can edit the rendering properties of the hub to achieve a similar result. The advantage of using a turbosurface is that you can redefine its location. For example, you could change the value of K in the current turbosurface to see Edge Length Ratio on a different nodal plane.

NoteYou can create new turbo surfaces. To begin the process of creating a new turbo surface, click Insert >User Defined > Turbo Surface.

NoteTo show distinct color bands, you could make a contour plot object that applies to an existing locator(geometric surface, turbo surface, or other graphic objects that involve surfaces). To begin the processof creating a contour plot, ensure that you have a suitable locator already defined, then click Insert >User Defined > Contour.

TipFor objects that are colored by a variable, it is best to view them with lighting turned off, so that thecolors are not altered according to the angle of view. The lighting is controlled by a setting on the Rendertab.

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Creating a LegendIn the previous section, you modified a turbo surface by coloring it according to Edge Length Ratio. To revealthe color map used to match values of Edge Length Ratio with particular colors, create a legend for the turbosurface:

1. Click Insert > User Defined > Legend.

2. Click OK to accept the default name.

3. Set Plot to TURBO SURFACE:Show Mesh.

4. Set Title Mode to Variable and Location.

5. Click Apply.

A legend appears in the viewer, showing the correspondence between values of Edge Length Ratio andcolors for the Show Mesh object.

You may want to modify 3D Mesh > Show Mesh to plot it on different locations, or to color it by differentvariables. The legend will be updated automatically whenever you make changes to the turbo surface.

Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to rotor37.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Click File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Creating a Legend

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Chapter 3. Steam StatorThis tutorial includes:

• Before You Begin (p. 20)

• Starting ANSYS TurboGrid (p. 20)

• Defining the Geometry (p. 20)

• Defining the Topology (p. 23)

• Reviewing the Mesh Data Settings (p. 23)

• Reviewing the Mesh Quality on the Hub and Shroud Layers (p. 23)

• Generating the Mesh (p. 25)

• Analyzing the Mesh (p. 25)

• Saving the Mesh (p. 27)

• Saving the State (Optional) (p. 27)

This tutorial teaches you how to:

• Import hub, shroud, and blade geometry from individual curve files.

• Change the method of constructing the hub and shroud curve types.

• Make fine adjustments to the mesh topology.

• Make colored surfaces to show variations in mesh measures (such as Minimum Face Angle).

As you work through this tutorial, you will create a mesh for a blade passage of a steam stator. A typical bladepassage is shown by the black outline in the figure below.

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The stator contains 60 blades distributed about the Z-axis. Within the blade passage, the maximum diameter of theshroud is approximately 97.5 cm.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/stator directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the GeometryIn the first tutorial, you loaded a BladeGen.inf file in order to specify the machine data (# of blade sets, rotationaxis, and units) and curve files. In this tutorial, you will enter such data manually using the Load Curves command.

Loading the CurvesLoad the curve files for the steam stator as follows:

1. Click File > Load Curves to open the Load TurboGrid Curves dialog box.

The Load TurboGrid Curves dialog box appears. ANSYS TurboGrid fills in the names of the curve filesbased on the files that are present in the working directory; The first .crv or .curve file found that has aname containing “hub”, ”shroud”, or “blade”/”profile” is selected as the hub, shroud, or blade file, respectively.

2. Set # of Bladesets to 60.

3. Set Rotation > Method to Principal Axis and Axis to Z.

4. Set Coordinates and Units > Coordinates to Cartesian and Length Units to cm.

These units are used to interpret the data in the curve files.

5. Ensure that, under TurboGrid Curve Files, Hub is set to ./hub.curve, Shroud is set to./shroud.curve, and Blade is set to ./profile.curve.

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Before You Begin

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6. Click OK to save the settings.

The progress bar at the bottom right of the screen shows the geometry generation progress. After the geometry hasbeen generated, you can see the hub, shroud, and blade for one passage. Along the blade, you can see the leadingand trailing edge curves (green and red lines, respectively). Near the blade, you can see the inlet and outlet markers(white octahedrons).

• Rotate the geometry into the position shown in Figure 3.1, “Incorrect Hub and Shroud Representations” (p. 22).

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Loading the Curves

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Figure 3.1. Incorrect Hub and Shroud Representations

As shown in Figure 3.1, “Incorrect Hub and Shroud Representations” (p. 22), the hub and shroud are greatlydistorted. This is the result of using spline curves to construct the hub and shroud based on relatively few data points.This problem will be corrected in the next section.

Modifying the Curve TypeChange the method of constructing the hub and shroud as follows:

1. Open Geometry > Hub.

2. Change Curve Type from Bspline to Piece-wise linear.

3. Click Apply.

4. Edit Shroud in the same way.

Intermediate points were created for the outlet. Because these points can have a dependence on the shapes ofthe hub and shroud curves, and because the latter were changed, regenerate the outlet points:

5. Open Geometry > Outlet.

6. Click Generate intermediate points .

7. When you are notified that intermediate points will be deleted, click Yes to continue.

NoteNote that the intermediate outlet points disappear. This happens because the regenerated set ofoutlet points happens to contain no intermediate points.

This completes the geometry definition.

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Defining the TopologyFor this steam stator mesh, H/J/C/L-Grid is an appropriate topology choice.

1. Click Hide all geometry objects to turn off the visibility of the geometry.

2. Open Topology Set.

3. Set Topology Definition > Method to H/J/C/L-Grid.

4. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

5. Set Include O-Grid > Width Factor to 0.15.

It is necessary to make the O-grid thinner than the default value of 0.5 because the blade is not much thinnerthan the passage.

6. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

7. Click Apply to set the topology.

8. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology appears on the hub and shroud as a structure of thick lines. Thinner lines showa preview of the mesh elements.

It is recommended that you freeze the topology after you specify and generate it. This prevents the settings on theAdvanced Parameters tab of Topology Set > Blade 1 from inadvertently changing due to changes to thegeometry or the topology distribution. For example, an adjustment to the position of an inlet point could cause achange to the number of topology blocks from the blade to the inlet.

1. Open Topology Set > Blade 1, visit the Advanced Parameters tab, and observe that no overrides existfor any of the settings.

2. Click the Freeze button.

Now all of the overrides are selected so that all of these settings will remain frozen (unless you manuallychange one).

NoteNote that the Freeze button has the same function whether you are on the Advanced Parameterstab or the Definition tab.

This completes the topology definition.

Reviewing the Mesh Data SettingsLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.

Reviewing the Mesh Quality on the Hub and ShroudLayers

Before generating the 3D mesh, it is recommended that you check the mesh quality on the layers. By correctingany mesh problems early, you can save time by minimizing the number of times you generate the full 3D mesh.

If the topology were grossly skewed or distorted on the hub or shroud layer, the Layers object would be shownwith red text in the object selector. Since the Layers object is shown in black text, the mesh contains no regionswith high skew on the hub or shroud.

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Defining the Topology

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Although the mesh has no areas with severe skew, improvements are still possible. In the next section, you willreduce the amount of skew by adjusting the topology distribution on the hub and shroud layers.

Modifying the Hub and Shroud LayersTo adjust the topology distribution on a layer, you can modify the position of a control point. Reduce the skew ofthe 2D mesh on the shroud layer by moving a control point as follows:

1. Zoom in on the region of the shroud layer shown in Figure 3.2, “Modification near Shroud TrailingEdge” (p. 24). If you are not sure which layer is the shroud layer, try toggling the visibility of Layers >Shroud.

2. Hold Ctrl+Shift and drag the control point as indicated by the displacement vector. The length of thedisplacement vector is a general guide for where to position the control point. Precise positioning of the pointis unnecessary.

Note

To select and drag control points without holding down Ctrl+Shift, you can click the Select

icon, then select and drag control points with the left mouse button.

Figure 3.2. Modification near Shroud Trailing Edge

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Modifying the Hub and Shroud Layers

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This movement of the control point helps to improve mesh element angles in the region around it.

3. Right-click Layers > Shroud and select Copy Control Points to Hub.

This causes the corresponding control point on the hub to move in a similar way.

You are now finished adjusting the topology distribution.

NoteIn a case that has more than two layers, you can modify the control points on the intermediate layers,but this is discouraged unless you intend to make no further changes to the hub and shroud layers.

NoteYou can change visibility settings for a layer using the object editor for that layer. By default, the mastertopology and refined mesh are visible. You can also make the (entire) topology visible. You can chooseto work with any combination of the visibility settings.

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

ANSYS TurboGrid automatically generates the recommended number of layers before the mesh is generated. Thisdefault behavior can be disabled by editing the Layers object by clearing Automatically generate requiredlayers at mesh creation on the Advanced Parameters tab.

A turbo surface of constant “K” (a nodal coordinate) appears. This surface is listed in the object selector as 3DMesh > Show Mesh. Later in this tutorial, you will change the location and coloring of this surface to explore themesh.

Analyzing the MeshCheck the 3D mesh statistics:

1. Open Mesh Analysis.

The mesh statistics shown here may differ slightly from what you see, mainly due to the freehand movementof the control point.

2. Double-click Maximum Element Volume Ratio to display the elements that have an element volumeratio greater than 2 (the default criterion set in the Mesh Analysis > Mesh Limits object).

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The Mesh Analysis > Show Limits volume object shows the areas in the mesh that do not meet thecriteria. For the Maximum Element Volume Ratio mesh measure, the volume object appears mainlyon the blade, hub, and shroud surfaces. This is normal. Note that part of the mesh downstream of the blade isalso included in the volume object. To improve the element volume ratio in this part of the mesh, you couldincrease the mesh density. However, it is not necessary to do this for the purposes of this tutorial.

3. Double-click Maximum Edge Length Ratio to display the elements that have an edge length ratiogreater than 100 (the default criterion).

The Mesh Analysis > Show Limits object appears mainly on the blade, hub and shroud surfaces. Thisis normal.

4. In the viewer, right-click the Show Limits object and click Set Turbosurface Position from the shortcutmenu.

The constant-“K” turbosurface (3D Mesh > Show Mesh) moves to the location where you right-clicked toinvoke the shortcut menu.

Another way to move this object is by editing its definition in the object editor.

5. Close the Mesh Statistics dialog box.

6. Turn off the visibility of Mesh Analysis > Show Limits.

Examining the Mesh QualitativelyThe predefined surfaces found under the 3D Mesh object in the object selector are useful for showing variationsin the mesh statistics.

In the following section, you will color 3D Mesh > Show Mesh by Minimum Face Angle. You will thencreate a legend for that object.

Editing a Turbo SurfaceTurbo Surfaces can be created by selecting Insert > User Defined > Turbo Surface. In this case, you will simplyedit the predefined turbo surface.

1. Open 3D Mesh > Show Mesh.

2. Leave Domains, Variable, and Value unchanged.

3. Click the Color tab and set Mode to Variable.

4. Set Variable to Minimum Face Angle.

5. Set Range to Local.

This will cause the range of colors in the color map to be distributed over the range of values found on theturbo surface, rather that over the global range or a user-defined range.

6. Click the Render tab.

7. Ensure that Draw Faces is selected.

8. Click Apply to apply the changes to the turbo surface.

Creating a LegendTo illustrate the scale of the Minimum Face Angle variable, create a legend for the turbo surface:

1. Click Insert > User Defined > Legend.

2. Click OK to accept the default name.

3. Set Plot to TURBO SURFACE:Show Mesh.

4. Set Title Mode to Variable and Location.

5. Leave the remaining settings unchanged.

6. Click Apply to create the legend.

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Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to steam_stator.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Click File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Saving the Mesh

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Page 37: Ansys Turbogrid

Chapter 4. Radial CompressorThis tutorial includes:

• Before You Begin (p. 30)

• Starting ANSYS TurboGrid (p. 30)

• Defining the Geometry (p. 30)

• Defining the Topology (p. 33)

• Reviewing the Mesh Data Settings (p. 34)

• Reviewing the Mesh Quality on the Hub and Shroud Layers (p. 34)

• Generating the Mesh (p. 36)

• Analyzing the Mesh (p. 36)

• Saving the Mesh (p. 37)

• Saving the State (Optional) (p. 37)

This tutorial teaches you how to:

• Set machine data and load curve files independently.

• Specify a “cut-off or square” edge on a blade.

• Add a control point to help govern the topology.

• Switch to a Blade-to-Blade (Theta-M') projection in the viewer.

As you work through this tutorial, you will create a mesh for a blade passage of a radial compressor blade row. Atypical blade passage is shown by the black outline in the figure below.

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The blade row contains 9 blades that revolve about the negative Z-axis. The blades are flank milled, and have cut-offtrailing edges. Within the blade passage, the maximum diameter of the shroud is approximately 125 mm.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/radcomp directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the GeometryIn the Rotor 37 tutorial, you loaded a BladeGen.inf file in order to specify the machine data (# of blade sets,rotation axis, and units) and the hub, shroud, and blade curve files. In the Steam Stator tutorial, you entered the

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same data using the Load Curves command. In this tutorial, you will define the machine data and curve filesindividually, by editing the corresponding geometry objects.

Defining the Machine DataSet up the Machine Data object, which contains basic information about the geometry:

1. Open Geometry > Machine Data.

2. Set # of Bladesets to 9.

3. Set Base Units to mm.

4. Click Apply to save the settings.

Defining the Hub1. Open Geometry > Hub.

2. Set Length Units to mm.

3. Ensure that File Name is set to ./hub.curve from your working directory.

4. Click Apply.

Defining the Shroud1. Open Geometry > Shroud.

2. Set Length Units to mm.

3. Ensure that File Name is set to ./shroud.curve from your working directory.

4. Click Apply.

NoteIf you had loaded the BladeGen.inf file, the Curve Type settings for the Hub and Shroudobjects would have been set to Piece-wise linear instead of the default: Bspline. Eithersetting will work for this geometry.

At this point, the entire hub and shroud surfaces are shown. After a blade is defined (in the next step), the hub andshroud will be trimmed to show only one passage.

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Figure 4.1. Hub and Shroud of Radial Compressor

Defining the Blade1. Open Geometry > Blade Set > Blade 1.

2. Ensure that File Name is set to ./profile.curve.

3. Set Length Units to mm.

4. Set Geometric Representation > Method to Flank Milled.

When you apply the Flank Milled option, Lofting is set to Streamwise, Curve Type is set toPiece-wise Linear, and Surface Type is set to Ruled. The Flank Milled option is appropriate forthis geometry since there are 2 blade profiles and the data points correspond with each other in position aroundthe profile.

5. Under Trailing Edge Definition, select Cut-off or square.

This will more accurately represent the blade at the trailing edge.

6. Click Apply.

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The progress bar at the bottom right of the screen shows the geometry generation progress. After the geometry hasbeen generated, you can see the hub, shroud, and blade for one passage. Along the blade, you can see the leadingand trailing edge curves (green and red lines, respectively).

Defining the TopologyFor this radial compressor mesh, H/J/C/L-Grid is an appropriate topology choice.

1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

4. Leave Include O-Grid > Width Factor set to 0.5.

This makes the O-Grid thickness equal to half the average blade thickness. In general, a suitable value of theO-Grid thickness depends on the blade geometry, topology type, and mesh density. Trial-and-error adjustmentsare sometimes required to establish a good value when creating the first mesh for a particular blade.

5. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

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6. Click Apply to set the topology.

7. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology appears.

8. Click Freeze to freeze the topology settings.

This completes the topology definition.

Reviewing the Mesh Data SettingsLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.

Reviewing the Mesh Quality on the Hub and ShroudLayers

The Layers > Hub object is shown in red text in the object selector.

Modifying the Hub Layer1. Right-click a blank area in the viewer, and click Transformation > Blade-to-Blade (Theta-M') from the

shortcut menu.

This causes the viewer to use blade-to-blade coordinates instead of Cartesian coordinates, making it easier tosee the mesh topology. This coordinate system is angle-preserving and minimizes the effect of changing radiuson viewing and manipulation.

2. Click Hide all geometry objects .

3. Turn off the visibility of Layers > Shroud.

4. Open Layers > Hub.

5. Double-click Maximum Face Angle.

The face angles need improvement near the upstream end.

6. Move the master control point as indicated by the displacement vector in Figure 4.2, “Master Control PointAdjusted Near Hub Leading Edge” (p. 35).

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Figure 4.2. Master Control Point Adjusted Near Hub Leading Edge

7. Create a new control point by right-clicking the location shown in Figure 4.3, “Added Master Control PointAdjusted Near Hub O-Grid” (p. 36) and selecting Control Point > Insert Master.

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Modifying the Hub Layer

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Figure 4.3. Added Master Control Point Adjusted Near Hub O-Grid

8. Move the new control point as indicated by the displacement vector in Figure 4.3, “Added Master ControlPoint Adjusted Near Hub O-Grid” (p. 36).

This helps to reduce the skew of elements in the passage.

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

Analyzing the MeshCheck the 3D mesh statistics:

• Open Mesh Analysis.

The mesh statistics shown here may differ slightly from what you see, mainly due to the freehand movementof the control points:

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The mesh statistics are in reasonable shape for a coarse mesh.

You can double-click one of the items in red to see the locations in the mesh where the statistics fail to meet thecriteria set in Mesh Analysis > Mesh Limits. Further improvements to the mesh are possible, but are beyondthe scope of this tutorial.

Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to radial_compressor.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Click File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Chapter 5. Axial FanThis tutorial includes:

• Before You Begin (p. 40)

• Starting ANSYS TurboGrid (p. 40)

• Defining the Geometry (p. 40)

• Defining the Topology (p. 42)

• Reviewing the Mesh Data Settings (p. 43)

• Reviewing the Mesh Quality on the Hub and Shroud Tip Layers (p. 43)

• Generating the Mesh (p. 44)

• Analyzing the Mesh (p. 44)

• Adding Inlet and Outlet Domains (p. 45)

• Regenerating the Mesh (p. 45)

• Analyzing the New Mesh (p. 45)

• Saving the Mesh (p. 45)

• Saving the State (Optional) (p. 46)

This tutorial teaches you how to:

• Switch to a Meridional (A-R) projection in the viewer.

• Change the shape and position of the Inlet and Outlet geometry objects which bound the blade passage inthe streamwise direction.

• Specify the use of a General Grid Interface on the periodic surfaces of the blade passage.

• Extend the mesh by adding inlet and outlet domains.

As you work through this tutorial, you will create a mesh for a blade passage of a fan. A typical blade passage, inletdomain, and outlet domain, are shown by the black outline in the figure below.

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The fan contains 10 blades that revolve about the negative Z-axis. A clearance gap exists between the blades andthe shroud, with a width of 5% of the total span. The shroud diameter is approximately 26.4 cm.

Let the mesh contain an inlet domain and an outlet domain.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/fan directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the GeometryTo obtain the basic geometry, you will load a BladeGen.inf file. After inspecting the geometry and improvingthe shape of the inlet and outlet, you will finish defining the geometry by creating the required gap between theblade and the shroud.

Load the BladeGen.inf file, then inspect the geometry by viewing it in axial-radial coordinates:

1. Click File > Load BladeGen.

2. Open BladeGen.inf from the working directory.

3. Right-click a blank area in the viewer, and click Transformation > Meridional (A-R) from the shortcut menu.

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The passage inlet, which appears in the object selector as Geometry > Inlet, is the upstream end of the bladepassage (but not necessarily the upstream end of the mesh, since, as you will see in this tutorial, you can add aninlet domain upstream of the passage inlet). The passage inlet is generated by revolving a curve, which is definedin an axial-radial plane, about the machine axis. That curve is, in turn, generated according to a set of points, knownhere as inlet points. These points appear as white octahedrons in the viewer. The passage outlet is analogous to thepassage inlet, and is downstream of the blade passage.

Notice that, in this case, there are two inlet points and they are located at different distances from the blade. In orderto obtain a high-quality mesh topology for the blade passage, the inlet points should be repositioned.

The outlet points should also be repositioned; they should be moved closer to the blade to reduce the aspect ratioof mesh elements immediately downstream of the blade trailing edge, as shown in Figure 5.1, “Effect of MovingPassage Outlet Towards Blade” (p. 42).

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Figure 5.1. Effect of Moving Passage Outlet Towards Blade

Reposition the inlet and outlet points as follows, and observe the movement of the inlet and outlet points in theviewer:

1. Open Geometry > Inlet.

2. Select Low Hub Point, then set Method to Set A and Location to -0.008.

3. Click Apply.

4. Select Low Shroud Point, then set Method to Set A and Location to 0.002.

5. Click Apply.

6. Open Geometry > Outlet.

7. Select Low Hub Point, then set Method to Set A and Location to 0.03.

8. Click Apply.

9. Select Low Shroud Point, then set Method to Set A and Location to 0.03.

10. Click Apply.

To complete the geometry, create a small gap between the blade and the shroud. The blade should be shortened to95% of its original span because the gap width, as specified in the problem description, is 5% of the total span.

1. Open Geometry > Blade Set > Shroud Tip.

2. Set Tip Option to Constant Span.

3. Set Span to 0.95.

4. Click Apply.

Defining the TopologyFor this fan mesh, H/J/C/L-Grid is an appropriate topology choice.

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Defining the Topology

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1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

4. Set Include O-Grid > Width Factor to 0.3.

This will specify the O-Grid thickness to be approximately equal to 30% of the average blade width. This valueis smaller than the default value of 0.5 because of the relatively short distance between the blades, comparedto the blade thickness, at the hub.

5. Set One-to-one Interface Ranges > Periodic to None.

This allows the nodes to be misaligned across the periodic interface; the nodes on one periodic surface are notrequired to connect in a one-to-one fashion with the nodes on the other periodic surface. When you set up theresulting mesh in a CFD simulation, a General Grid Interface will be required to connect the periodic surfaces.While such an interface may require more processing time and may be less accurate than a one-to-one interface,the benefit of using a GGI interface is that the passage mesh can be made with less skew. This setting is oftenbeneficial when the blade has a high stagger angle.

6. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

7. Click Apply to set the topology.

8. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

9. Click Freeze to freeze the topology settings.

This completes the topology definition.

Reviewing the Mesh Data SettingsLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.

As prescribed in the problem description, the mesh should contain an inlet domain and an outlet domain. For now,leave the Inlet Domain and Outlet Domain check boxes cleared; you will select these check boxes later in thistutorial. The inlet domain contains some degenerate elements where the hub reaches zero radius. The degenerateelements affect the mesh statistics, and make it more difficult to analyze the quality of the rest of the mesh.

Reviewing the Mesh Quality on the Hub and ShroudTip Layers

The Layers > Shroud Tip object is shown in red text in the object selector.

Modifying the Shroud Tip Layer1. Right-click a blank area in the viewer, and click Transformation > Blade-to-Blade (Theta-M') from the

shortcut menu.

This causes the viewer to use blade-to-blade coordinates, making it easy to see the mesh topology. Thiscoordinate system is angle-preserving and minimizes the effect of changing radius on viewing and manipulation.

2. Click Hide all geometry objects .

3. Turn off the visibility of Layers > Hub.

4. Open Layers > Shroud Tip.

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Reviewing the Mesh Data Settings

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5. Double-click Maximum Face Angle.

The face angles need improvement near the upstream end.

6. Move the master control point as indicated by the displacement vector in Figure 5.2, “Master Control PointsAdjusted on Shroud Tip Layer” (p. 44).

Figure 5.2. Master Control Points Adjusted on Shroud Tip Layer

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

Analyzing the MeshCheck the 3D mesh statistics:

1. Open Mesh Analysis.

The mesh statistics shown here may differ slightly from what you see, mainly due to the freehand movementof the control points:

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The mesh statistics are in reasonable shape for a coarse mesh.

2. Right-click a blank area in the viewer, and click Transformation > Cartesian (X-Y-Z) from the shortcutmenu.

You can double-click one of the items in red to see the locations in the mesh where the statistics fail to meet thecriteria set in Mesh Analysis > Mesh Limits. Further improvements to the mesh are possible, but are beyondthe scope of this tutorial.

Adding Inlet and Outlet DomainsAs specified in the problem description, the mesh should contain an inlet domain and an outlet domain. Add thesenext:

1. Open Mesh Data.

2. On the Mesh Size tab, select Inlet Domain and Outlet Domain.

3. Click Apply.

Regenerating the MeshAfter specifying that inlet and outlet domains should be added, the original mesh was deleted. Generate the newmesh:

• Click Insert > Mesh.

Analyzing the New Mesh1. Open Mesh Analysis. Note that the Maximum Edge Length Ratio mesh measure is extremely

large. By displaying this mesh measure, you will see that some of the mesh elements that exceed the criterionare those at the inlet where the mesh meets the rotation axis. This is expected, since the element edges at thislocation have zero length. This is normal and expected wherever the hub reaches the axis of rotation.

2. View the mesh on the inlet and outlet (not the passage inlet and outlet, but the inlet and outlet of the entiremesh) by turning on the visibility of the corresponding 3D Mesh objects.

Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

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4. Set File name to fan.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Click File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Saving the State (Optional)

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Chapter 6. Splitter BladesThis tutorial includes:

• Before You Begin (p. 48)

• Starting ANSYS TurboGrid (p. 48)

• Defining the Geometry (p. 48)

• Defining the Topology (p. 49)

• Reviewing the Topology Settings (p. 49)

• Reviewing the Mesh Data Settings (p. 49)

• Reviewing the Mesh Quality on the Hub and Shroud Layers (p. 49)

• Generating the Mesh (p. 50)

• Analyzing the Mesh (p. 51)

• Saving the Mesh (p. 51)

• Saving the State (Optional) (p. 51)

This tutorial teaches you how to:

• Review the topology type for each blade.

• Create a mesh involving splitter blades.

As you work through this tutorial, you will create a mesh for a blade set of a centrifugal compressor that has splitterblades. A typical blade set is shown by the black outline in the figure below.

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The blade row contains 7 blade sets, each containing one main blade and one splitter blade. The blade row revolvesabout the negative Z-axis. The blades are flank milled and have cut-off trailing edges. Within the blade passage,the maximum diameter of the shroud is approximately 13 cm.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/splitter directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the GeometryLoad the BladeGen.inf file:

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1. Click File > Load BladeGen.

2. Open BladeGen.inf from the working directory.

Defining the TopologyFor this compressor mesh, H/J/C/L-Grid is an appropriate topology choice.

1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

4. Leave Include O-Grid > Width Factor set to 0.5.

This makes the O-Grid thickness equal to half the average blade thickness. In general, a suitable value of theO-Grid thickness depends on the blade geometry, topology type, and mesh density. Trial-and-error adjustmentsare sometimes required to establish a good value when creating the first mesh for a particular blade.

5. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

6. Click Apply to set the topology.

7. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

8. Click Freeze to freeze the topology settings.

This completes the topology definition.

Reviewing the Topology SettingsTo see which topology types ANSYS TurboGrid used for the upstream and downstream ends of each of the twoblade passages, do the following:

1. Open Topology Set > Main Blade and click the Advanced Parameters tab.

Note that ANSYS TurboGrid has selected a J-Grid topology for the leading edge, and an H-Grid topology forthe trailing edge. The J-Grid is more suitable than the H-Grid for the leading edge because of the higher bladeangle.

2. Open Topology Set > Splitter Blade 1 and click the Advanced Parameters tab.

Note that ANSYS TurboGrid has selected an H-Grid topology for both ends of the splitter blade.

Reviewing the Mesh Data SettingsLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.

Reviewing the Mesh Quality on the Hub and ShroudLayers

The Layers > Hub object is shown in red text in the object selector.

Modifying the Hub Layer1. Right-click a blank area in the viewer, and click Transformation > Blade-to-Blade (Theta-M') from the

shortcut menu.

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Defining the Topology

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This causes the viewer to use blade-to-blade coordinates, making it easy to see the mesh topology. Thiscoordinate system is angle-preserving and minimizes the effect of changing radius on viewing and manipulation.

2. Click Hide all geometry objects .

3. Turn off the visibility of Layers > Shroud.

4. Open Layers > Hub.

5. Double-click Maximum Face Angle.

The face angles need improvement near the upstream end.

6. Move the master control point as indicated by the displacement vector in Figure 6.1, “Master Control PointAdjusted Near Hub Leading Edge” (p. 50).

Figure 6.1. Master Control Point Adjusted Near Hub Leading Edge

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

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Analyzing the MeshCheck the 3D mesh statistics:

• Open Mesh Analysis.

The mesh statistics shown here may differ slightly from what you see, mainly due to the freehand movementof the control points:

The mesh statistics are in reasonable shape for a coarse mesh.

You can double-click one of the items in red to see the locations in the mesh where the statistics fail to meet thecriteria set in Mesh Analysis > Mesh Limits. Further improvements to the mesh are possible, but are beyondthe scope of this tutorial.

Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to compressor_splitter.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Select File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Chapter 7.Tandem VaneThis tutorial includes:

• Before You Begin (p. 54)

• Starting ANSYS TurboGrid (p. 54)

• Defining the Geometry (p. 55)

• Defining the Topology (p. 55)

• Reviewing the Topology Settings (p. 55)

• Reviewing the Mesh Data Settings (p. 56)

• Reviewing the Mesh Quality on the Hub and Shroud Layers (p. 56)

• Increasing the Mesh Density (p. 59)

• Further Modifying the Hub Layer (p. 60)

• Generating the Mesh (p. 62)

• Saving the Mesh (p. 62)

• Saving the State (Optional) (p. 62)

This tutorial teaches you how to:

• Load geometry data from a CFG file.

• Copy control points and their custom positional offsets from one topology layer to another.

• Use “sticky” control points.

• Create a mesh involving tandem vanes.

As you work through this tutorial, you will create a mesh for a blade set of a radial machine component that hastandem vanes. A typical blade set is shown by the black outline in the figure below.

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The component has 16 blade sets, each containing one main blade and one tandem vane. A clearance gap existsbetween each blade and the shroud. Within the blade passages, the maximum diameter of the shroud is approximately52.2 cm.

You will begin by loading the geometry from a CFG file. You will define the mesh topology with settings that helpto reduce mesh skew by making the mesh around each blade more independently-controlled. Finally, you will adjustthe topology and generate a fine (high-resolution) mesh.

In order to avoid long processing times, you will establish a reasonable topology before specifying a fine meshdensity.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/tandem directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

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Defining the GeometryLoad the tandem.cfg file using units of cm, then remove the shroud clearance gap from the main blade inaccordance with the problem description:

1. Select File > Load CFG.

2. In the top-right corner of the Load CFG File dialog box, set Length Units to cm.

ANSYS TurboGrid will interpret the numerical data in the CFG file using these units.

3. Open tandem.cfg from the working directory.

Defining the TopologyFor this tandem vane mesh, H/J/C/L-Grid is an appropriate topology choice.

1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

4. Set Include O-Grid > Width Factor to 0.1.

This will specify the O-Grid thickness to be approximately equal to 10% of the average blade width. This valueis smaller than the default value of 0.5 because of the relatively short distance between the blades, comparedto the blade thickness.

5. Set One-to-one Interface Ranges > Periodic to None.

The periodic interface is the interface between blade sets.

6. Set One-to-one Interface Ranges > Passage to None.

The passage interface is the interface between the blade passages in the blade set.

The Periodic and Passage interface range settings, when set to None, allow the nodes to be misaligned acrossthe respective interface; the nodes on one side of an interface are not required to connect in a one-to-one fashionwith the nodes on the other side of the interface. When you set up the resulting mesh in a CFD simulation, aGeneral Grid Interface will be required to connect the periodic surfaces. While such an interface may requiremore processing time and may be less accurate than a one-to-one interface, the benefit of using a GGI interfaceis that the passage meshes can be adjusted independently of each other. This setting is often beneficial forturbomachinery components that have tandem vanes. You could run this tutorial with Periodic and Passageset to Full, but the process of setting the topology distribution would be more difficult (and for somegeometries, impossible).

7. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

8. Click Apply to set the topology.

9. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

10. Click Freeze to freeze the topology settings.

This completes the topology definition.

Reviewing the Topology SettingsTo see which topology types ANSYS TurboGrid used for the upstream and downstream ends of each of the twoblade passages, do the following:

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1. Open Topology Set > Main Blade and click the Advanced Parameters tab.

Note that ANSYS TurboGrid has selected a J-Grid topology for both ends of the main blade.

2. Open Topology Set > Blade Blade 1 and click the Advanced Parameters tab.

Note that ANSYS TurboGrid has selected a J-Grid topology for the leading edge, and an H-Grid topology forthe trailing edge. The H-Grid is more suitable than the J-Grid for the trailing edge because of the lower bladeangle.

Reviewing the Mesh Data SettingsLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.Later in this tutorial, you will specify a fine mesh. By leaving the mesh coarse for now, you will reduce processingtime while adjusting the topology.

Reviewing the Mesh Quality on the Hub and ShroudLayers

The Layers > Hub and Layers > Shroud Tip objects are shown in red text in the object selector.

In this case, the main problem is a high amount of skew in the mesh upstream of the tandem vane. This problemwill be fixed by moving and adding control points.

Modifying the Hub LayerIdentify problem areas on the hub layer and adjust the topology accordingly:

1. Click Hide all geometry objects .

2. Right-click a blank area in the viewer, and select Predefined Camera > View Towards +Z from the shortcutmenu.

3. Turn off the visibility of Layers > Shroud Tip.

4. Open Layers > Hub.

5. Double-click Minimum Face Angle.

Observe the areas that are marked as red. These areas have face angles that are too small.

6. Zoom in on the area shown in Figure 7.1, “Moving a Control Point on the Hub Layer” (p. 57).

7. Move the master control point as indicated by the displacement vector in Figure 7.1, “Moving a Control Pointon the Hub Layer” (p. 57).

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Figure 7.1. Moving a Control Point on the Hub Layer

8. Double-click Minimum Face Angle to refresh the display of areas that still require adjustments.

9. Insert a master control point at the top of the red area, then move it as indicated by the displacement vector inFigure 7.2, “Inserting and Moving a Control Point on the Hub Layer” (p. 58):

1. Right-click the location where the new control point is to be added.

2. Select Control Point > Insert Master.

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Figure 7.2. Inserting and Moving a Control Point on the Hub Layer

10. Double-click Minimum Face Angle and then Maximum Face Angle to see which area of the hubrequires improvement.

There is an area of high skew, shown in the left side of Figure 7.3, “Inserting and Moving Another ControlPoint on the Hub Layer” (p. 59), that may or may not be shown in red (because the face angles are near thelimit established in the Mesh Analysis > Mesh Limits object).

11. Insert a master control point and move it as shown in Figure 7.3, “Inserting and Moving Another Control Pointon the Hub Layer” (p. 59).

The control point is on the interface between blades and belongs to the tandem vane blade passage. You mayneed to zoom in and turn on the topology visibility (in the Layers > Hub object) to insert the point at thedesired location. The desired location of the point to be inserted is at the intersection of the topology line thatyou want to move and the topology line on the interface between the adjacent passages. If you have chosenthe correct location, a red line that shows the range of influence of the new control point will stretch into thepassage for the tandem vane; if the red line stretches downward into the main blade passage, click Edit > Undoand try again.

Note that you are moving the new control point past a control point in the main passage. This is possiblebecause One-to-one Interface Ranges > Passage is set to None, meaning that the interface is a GGI interface.

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Modifying the Hub Layer

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Figure 7.3. Inserting and Moving Another Control Point on the Hub Layer

12. Confirm that the mesh statistics have improved for the Hub layer.

Make further adjustments as necessary in order to achieve an acceptable range of face angles. Confirm thatthe only elements that exceed the maximum aspect ratio are those next to the blade surfaces.

Modifying the Shroud Tip LayerIdentify problem areas on the shroud tip layer and adjust the topology accordingly:

1. Turn off the visibility of Layers > Hub.

2. Turn on the visibility of Layers > Shroud Tip.

3. Click the Fit View icon.

4. Open Layers > Shroud Tip.

5. Examine the mesh statistics and note any problem areas.

6. Right-click the Hub layer object in the object selector, then select Copy Control Points to Shroud.

The control point adjustments you made to the hub layer, and the newly-created control point, are copied tothe shroud tip layer. The mesh statistics improve on the shroud tip layer as a result of this operation.

Increasing the Mesh DensityAs mentioned at the beginning of this tutorial, you will increase the mesh density. Such an increase in mesh densitycan result in a more accurate CFD solution.

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Modifying the Shroud Tip Layer

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1. Open Mesh Data.

2. On the Mesh Size tab, leave Method set to Target Passage Mesh Size.

3. Set Node Count to Fine (250000).

4. Click Apply.

Further Modifying the Hub LayerAs a result of changing the mesh density, the mesh quality on the hub layer has changed slightly. A portion of thehub layer now contains elements with unacceptable face angles.

Fix the hub layer:

1. Turn off the visibility of Layers > Shroud Tip.

2. Turn on the visibility of Layers > Hub.

3. Click Fit View .

4. Open Layers > Hub.

5. Examine the mesh statistics and note the area with bad face angles downstream of the main blade, as shownin Figure 7.4, “Poor Face Angles” (p. 60).

Figure 7.4. Poor Face Angles

6. In preparation for the next step, make the two control points that are located slightly downstream of the mainblade “sticky” by right-clicking each one and selecting Sticky.

These two points are circled in Figure 7.5, “Making Control Points “Sticky”” (p. 61).

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Figure 7.5. Making Control Points “Sticky”

7. Add two master control points further downstream on the same master topology lines, then move them asshown in Figure 7.6, “Adding and Moving Control Points” (p. 62).

As you move these control points, the other control points that you previously made sticky remain stationarybecause they are sticky. If they were not sticky, they would move because they are on the line of influence ofthe added master control points.

NoteA sticky control point will not remain stationary if you move a pre-defined master control point onthe same master topology line.

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Figure 7.6. Adding and Moving Control Points

Confirm that the mesh measures are acceptable.

Generating the MeshNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to tandem.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

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1. Select File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Saving the State (Optional)

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Chapter 8. Batch Mode StudiesNoteThis tutorial requires using ANSYS TurboGrid in batch mode, which is not possible from ANSYSWorkbench.

This tutorial has two parts:

• Part 1: Parametric Study (p. 65)

• Part 2: Grid Refinement (p. 68)

Part 1 of this tutorial demonstrates one basic way of performing a parametric study using ANSYS TurboGrid inbatch mode: using a script loop to repeatedly modify and run a session file with ANSYS TurboGrid. Each modifiedsession file loads a baseline state file, reloads the blade geometry from a different file, and generates and savesoutput (including a mesh).

Part 2 of this tutorial demonstrates a grid refinement study using a method similar to part 1. The main difference inpart 2 is the use of the “end ratio” option throughout the mesh data specification to allow the grid refinement tooccur evenly through the mesh.

Variations of the algorithm described in this tutorial are possible. For example:

• You could modify the state file instead of the session file.

• You could use a loop within a session file (written in Perl) to avoid loading and closing ANSYS TurboGridrepeatedly, which should improve efficiency.

Such variations are beyond the scope of this tutorial. You are encouraged to try the algorithm used in this tutorialand then explore other methods as required in order to meet your specific requirements.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Part 1: Parametric StudyThis part of the tutorial includes:

• Starting ANSYS TurboGrid (p. 65)

• Defining the Geometry (p. 65)

• Creating the Topology and Modifying the Mesh (p. 66)

• Creating the Session File (p. 66)

• Running the Session File (p. 67)

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/rotor37 directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the Geometry1. Select File > Load BladeGen.

2. Open the BladeGen.inf file.

3. Select File > Load Curves.

4. Set TurboGrid Curve Files > Blade to profile.1.curve.

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5. Click OK to load the geometry.

6. Edit Geometry > Blade Set > Shroud Tip to use the Constant Span tip option and leave Spanset to the default value.

7. Click Apply.

Creating the Topology and Modifying the Mesh1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Click Apply to set the topology.

4. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

5. Click Freeze to freeze the topology settings.

6. Double-click Mesh Data to open it for editing. All settings will be changed to use explicit node counts.

7. Apply the following settings

ValueOptionTab

Topology Block Edge SplitMethodMesh Size

Element Count and SizeSpanwise Blade Distribution Parameters >Method

Passage

Element Count and SizeO-Grid > Method

Element Count and SizeShroud Tip Distribution Parameters >Method

Shroud Tip

8. Click Apply.

9. Save the state to baseline_mesh.tst.

10. Quit ANSYS TurboGrid.

You now have a state file that sets up a mesh based on profile.1.curve.

The particular blade geometry used by the state file needs only to be representative of the geometries that will beused in the study because it will be overridden by what is specified in the session file, which is produced next.

Creating the Session File1. Start ANSYS TurboGrid.

2. Select Session > New Session from the menu bar to create a new session named generate_mesh.tse.

3. Start recording to the session file by clicking Start Recording .

4. Load the state file that was saved earlier (baseline_mesh.tst).

The session is now at the point where you would typically make a change to the state. In this case, the changewill be to select a new blade curve file. To be able to load a new file, the CCL (CFX Command Language)block responsible for loading the geometry will be included in the session file at this point; you will create thisCCL block in the next step. With that block created, you can create a script to control which blade geometryfile is loaded by changing the name of the file within the CCL block. (The script creation is in the next section.)

5. Open Geometry > Blade Set > Blade 1 for editing and click Apply without changing any settings.

6. Click Insert > Mesh.

7. Select File > Save Mesh As and save the mesh with filename mesh.1.gtm with File type set to ANSYSCFX and Export Units set to cm.

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8. Select Tools > Command Editor and enter the following lines in the Command Editor dialog box:

! $minFAngle = minVal("Minimum Face Angle", "/DOMAIN:Passage")*180/3.14159;! open F,"> mesh_statistics.1.txt";! print F "minimum face angle in Passage mesh: $minFAngle\n";! close F;

9. Click Process, then Close. This adds Power Syntax commands that cause Minimum Face Angle to bewritten to a file.

10. Stop recording the session file by clicking Stop Recording .

11. Exit ANSYS TurboGrid.

A prompt will suggest that you save the state. You do not have to save the state since this was done earlier.

You now have a session file that loads the baseline state file, reloads the blade geometry, creates a mesh, saves themesh, and generates statistical output for the mesh.

Running the Session File1. Using a basic text editor, write a script that, in a loop, modifies the blade file name in the session file, and runs

each modified session file using ANSYS TurboGrid in batch mode. You may give this file any name. Thescript shown here is written in Perl:

NoteThis script defines and uses a variable, turbogrid, which must be defined as the full path nameto the cfxtg.exe in the bin directory of the ANSYS TurboGrid installation.

#!/usr/bin/perl# Point to the location of the cfxtg.exe (full pathname),# usually in <CFXROOT>/bin/$turbogrid = "C:/Program Files/ANSYS Inc/v121/TurboGrid/bin/cfxtg.exe";# Initialize the input and output session filenames.$base_tse = "generate_mesh.tse";$output_tse = "gen_mesh.tse";

# Get the baseline session file data.open(BASE_FH, "<$base_tse")or die "Can't open file (${base_tse}) for input: $!";@session_data = <BASE_FH>;close(BASE_FH);

# Loop over each blade geometry file.foreach $loopindex(1,2){ # Make a copy of the baseline session file # so we don't destroy the original template. @copy_data = @session_data;

# Write a session file (based on the original session file) that is # customized to use the blade associated with this loop. open(OUTPUT_FH, ">$output_tse") or die "Can't open file (${output_tse}) for output: $!"; foreach $line (@copy_data) { chomp($line); $line =~ s/\.1\./\.${loopindex}\./g; print OUTPUT_FH "$line\n";

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} close(OUTPUT_FH);

# Run TurboGrid in batch mode with the customized session file. (system("\"${turbogrid}\" -batch \"${output_tse}\"") == 0) or die "Batch run of TurboGrid failed ($?): $!";}exit 0;

2. Run the script shown above by opening a command prompt from the launcher (with the correct workingdirectory set) and entering the line:

perl <scriptname>

where <scriptname> represents the name of the script file.

The script will take a few minutes to run. When it completes, it will have written two .gtm files to your workingdirectory, as well as two text files containing the value of the minimum face angle.

Part 2: Grid RefinementThis part of the tutorial includes:

• Starting ANSYS TurboGrid (p. 68)

• Defining the Geometry and Topology (p. 68)

• Creating the Session File (p. 69)

• Running the Session File (p. 70)

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/rotor37 directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the Geometry and Topology1. Select File > Load BladeGen.

2. Open the BladeGen.inf file.

3. Edit Geometry > Blade Set > Shroud Tip to use the Constant Span tip option and leave Spanset to the default value. Remember to click Apply when finished.

4. Open Topology Set.

5. Set Topology Definition > Method to H/J/C/L-Grid.

6. Click Apply to set the topology.

7. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

8. Click Freeze to freeze the topology settings.

9. Double-click Mesh Data.

10. Apply the following settings

ValueOptionTab

Target Passage Mesh SizeMethodMesh Size

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ValueOptionTab

SpecifyNode Count

End RatioSpanwise Blade Distribution Parameters >Method

Passage

End RatioO-Grid > Method

Match Expansion at Blade TipShroud Tip Distribution Parameters >Method

Shroud Tip

11. Click Apply.

12. Save the state to baseline_mesh.tst.

13. Exit ANSYS TurboGrid.

You now have a state file that sets up a mesh based on the default value of the target mesh node count.

The particular mesh node count target used by the state file will be overridden by what is specified in a session file,which is produced next.

Creating the Session File1. Start ANSYS TurboGrid.

2. Create a new session named generate_mesh.tse.

3. Start recording to the session file by clicking Start Recording .

4. Load the state file that was saved earlier (baseline_mesh.tst).

The session is now at the point where you would typically make a change to the state. In this case, the changewill be to select a different target mesh node count. To be able to change the target mesh node count, the CCL(CFX Command Language) block responsible for specifying the mesh data settings will be included at thispoint in the session file; you will do this in the next step. With that block created, you can create a script tocontrol the target mesh node count by changing the Target Mesh Node Count CCL parameter in theCCL block. (The script creation is in the next section.)

5. Double-click Mesh Data to open it and click Apply without changing any settings.

6. Click Insert > Mesh.

7. Select File > Save Mesh As and save the mesh as outputmesh.1.gtm with File type set to ANSYS CFXand Export Units set to cm.

8. Select Tools > Command Editor and enter the following lines in the Command Editor dialog box:

! $minFAngle = minVal("Minimum Face Angle", "/DOMAIN:Passage")*180/3.14159;! $nodeCount = count("/DOMAIN:Passage");! open F,"> meshstatistics.1.txt";! print F "minimum face angle in Passage mesh: $minFAngle\n";! print F "number of nodes in Passage mesh: $nodeCount\n";! close F;

9. Click Process, then Close. This adds Power Syntax commands that cause Minimum Face Angle and thenode count to be written to a file.

10. Stop recording the session file by clicking Stop Recording .

11. Exit ANSYS TurboGrid.

A prompt will suggest that you save the state. You do not have to save the state since this was done earlier.

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You now have a session file that loads the baseline mesh state file, reapplies the Mesh Data settings, creates amesh, saves the mesh, and generates statistical output for the mesh.

Running the Session File1. Write a script that, in a loop, modifies the target passage node count in the session file, and runs each modified

session file using ANSYS TurboGrid in batch mode. The script shown here is written in Perl:

NoteIn the following script, the two lines following the commented line #### The next two lines... #### are meant to be entered as a single line. Also, this script defines and uses a variable,turbogrid, which must be defined as the full pathname to the cfxtg (cfxtg.exe) file in thebin directory of the installation.

#!/usr/bin/perl# Point to the location of the cfxtg.exe (full pathname),# usually in <CFXROOT>/bin/cfxtg.exe$turbogrid = "C:/Program Files/ANSYS Inc/v121/TurboGrid/bin/cfxtg.exe";# Initialize the input and output session filenames.$base_tse = "generate_mesh.tse";$output_tse = "gen_mesh.tse";# This is a list of the target node values to be used.@target_nodes = (50000, 100000, 200000);# Get the baseline session file data.open(BASE_FH, "<$base_tse")or die "Can't open file (${base_tse}) for input: $!";@session_data = <BASE_FH>;close(BASE_FH);# Loop over each target node value.$loopindex = 1;foreach $target (@target_nodes) { # Make a copy of the baseline session file # so we don't destroy the original template. @copy_data = @session_data; # Write a session file (based on the original session file) that is # customized to use the target node count associated with this loop. open(OUTPUT_FH, ">$output_tse") or die "Can't open file (${output_tse}) for output: $!"; foreach $line (@copy_data) { chomp($line); $line =~ s/\.1\./\.${loopindex}\./g;#### The next two lines should be combined into one single line. #### $line =~ s/Target Mesh Node Count = [0-9][0-9]*/Target Mesh Node Count = ${target}/g; print OUTPUT_FH "$line\n"; } close(OUTPUT_FH); # Run TurboGrid in batch mode with the customized session file. (system("\"${turbogrid}\" -batch \"${output_tse}\"") == 0) or die "Batch run of TurboGrid failed ($?): $!"; # Prepare for next loop iteration. $loopindex++;}exit 0;

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2. Run the script shown above by opening a command prompt from the launcher (with the correct workingdirectory set) and entering the line:

perl <scriptname>

where <scriptname> represents the name of the script file.

The script will take a few minutes to run. When it completes, it will have written some .gtm files to your workingdirectory, as well as some text files containing the value of the minimum face angle and the number of nodes in themesh.

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Chapter 9. Deformed TurbineThis tutorial includes:

• Before You Begin (p. 74)

• Starting ANSYS TurboGrid (p. 74)

• Mesh for the Deformed Blade Group (p. 74)

• Mesh for an Undeformed Blade (p. 87)

• Summary (p. 92)

• Further Exercise (p. 92)

This tutorial teaches you how to:

• Build a blade set by loading blades separately from files and rotating them into position.

• Save, load, and rotate periodic surfaces.

• Make separate and different meshes that are designed to fit together in a CFD simulation.

As you work through this tutorial, you will create meshes for modeling an axial turbine blade row that has a deformedblade. The technique learned here can be extended to model a blade row with several deformed blades. A blade canbecome deformed after being damaged, for example by the passage of a foreign object.

The blade row contains 71 blades, one of which is deformed. The blade row revolves about the Z-axis. A clearancegap exists between the blades and the shroud, with a width of 0.05 cm. Within the blade passage, the maximumdiameter of the shroud is approximately 56 cm.

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In this case, the full 360° geometry needs to be modeled. You will accomplish this by producing a pair ofcomplementary meshes: one mesh for a blade group consisting of a deformed blade between two undeformed blades,and one mesh for a single undeformed blade. By using 68 instances of the mesh for the undeformed blade, the entireblade row can be modeled.

For compatibility between the two meshes, the mesh density should be comparable. In this case, choose a meshdensity of about 250000 nodes per blade. You will also have to ensure that the interface between the meshes hasthe same shape.

Let each mesh contain an inlet domain and an outlet domain.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/deformed directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Mesh for the Deformed Blade GroupIn this part of the tutorial you will create a mesh for one deformed turbine blade surrounded by one undeformedblade on each side.

Defining the Geometry for the Deformed Blade Group

Loading an Undeformed BladeYou will use the provided BladeGen.inf file to load the geometry for an undeformed turbine blade.

1. Click File > Load BladeGen.

2. Open BladeGen.inf from the working directory.

A blade passage for an undeformed blade appears in the viewer.

Moving the Periodic SurfacesThe BladeGen.inf file specifies a machine with 71 blade sets, each containing one blade. The blades are thereforespaced at (360/71)° intervals around the machine axis.

In the next section, you will insert two blades into the blade set to form a group of three blades. Specifically, youwill insert a deformed blade, then an undeformed blade, both on the same side of the existing undeformed blade.The result will be a group of blades with one deformed blade between two undeformed blades.

Before inserting the blades, make room for them by widening the angular separation between the periodic surfacesfrom (360/71)° to (3*360/71)°:

1. Open Geometry > Machine Data.

2. Change Pitch Angle > Method to Specified Angle.

3. Set Pitch Angle > Angle to 15.21127 degrees.

4. Click Apply.

The periodic surfaces are now (3*360/71)° apart.

Inserting Two More BladesInsert two blades into the blade set so that there is one deformed blade surrounded by two undeformed blades:

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1. Insert a blade named Deformed Blade:

1. Right-click Geometry > Blade Set and click Insert > Blade.

2. Set Name to Deformed Blade and click OK.

The tree view displays Deformed Blade in a bold, italic, blue font (white when selected). This indicatesthat the object requires more information. In particular, the file name reference and/or the position of the blademust be changed so that the new blade is different from the original blade.

2. Enter the following settings for Deformed Blade:

ValueSettingTab

deformed.curveFile NameBlade

(Selected)Axial RotationTransform

5.070423 [degree]Axial Rotation > Angle

3. Click Apply.

The tree view now displays Deformed Blade in plain black text. This indicates that the object now has allthe required information.

4. Insert a blade named Blade 3.

5. Enter the following settings for Blade 3:

ValueSettingTab

profile.curveFile NameBlade

(Selected)Axial RotationTransform

10.140845 [degree]Axial Rotation > Angle

6. Click Apply.

You now have a blade set with three blades, as shown in Figure 9.1, “Blade Set Containing a Deformed Blade” (p. 76).

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Figure 9.1. Blade Set Containing a Deformed Blade

Adding a Shroud TipAs stated in the problem description, the blade set requires a blade tip clearance of 0.05 cm at the shroud. Add thisclearance by editing the Shroud Tip object:

1. Open Geometry > Blade Set > Shroud Tip.

2. Enter the following settings for Shroud Tip:

ValueSettingTab

Normal DistanceClearance Type > Tip OptionShroud Tip

0.05 [cm]Clearance Parameter > Tip Clearance

3. Click Apply.

ANSYS TurboGrid requires, and uses, the same shroud tip clearance for all blades in the blade set. The shroud tipsof all blades in the blade set lie on the same surface of revolution when revolved about the axis of rotation.

Adjusting the Inlet and Outlet PointsThe inlet and outlet points need to be moved. To see why, change to a meridional transform:

• Right-click a blank area in the viewer, and click Transformation > Meridional (A-R) from the shortcut menu.

With the inlet points in their initial positions, the inlet domain (the portion of the mesh upstream of the inlet points)is much larger at the shroud than at the hub, as measured in the axial direction. To reduce this variation, move theinlet points closer to the blade:

• Move the inlet points as shown in Adjusting the Inlet Points (p. 77):

1. Open Geometry > Inlet.

2. Enter the following settings for Low Hub Point:

ValueSettingTab

Low Hub PointaCurveInlet

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ValueSettingTab

Set ACurve > Method

0.045Curve > Location

aThe word “Low” in “Low Hub Point” refers to the side of the passage in terms of the Theta coordinate. The “Low Hub Point” inletpoint is at the intersection of the hub and the inlet curve on the low-Theta side of the passage. Note that the Theta coordinate cannotbe seen in the Meridional (A-R) transform.

3. Click Apply.

4. Enter the following settings for Low Shroud Point:

ValueSettingTab

Low Shroud PointCurveInlet

Set ACurve > Method

0. 055Curve > Location

5. Click Apply.

Figure 9.2. Adjusting the Inlet Points

For consistency, move the outlet points closer to the blade:

• Move the outlet points as shown in Adjusting the Outlet Points (p. 78):

1. Open Geometry > Outlet.

2. Enter the following settings for Low Hub Point:

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ValueSettingTab

Low Hub PointCurveOutlet

Set ACurve > Method

0.099Curve > Location

3. Click Apply.

4. Enter the following settings for Low Shroud Point:

ValueSettingTab

Low Shroud PointCurveOutlet

Set ACurve > Method

0. 089Curve > Location

5. Click Apply.

Figure 9.3. Adjusting the Outlet Points

Saving the Periodic/Interface SurfacesSave the periodic and interface surfaces to files for later use:

1. Click File > Save > Periodic/Interface Surfaces.

The Save Interfaces dialog box appears.

2. Ensure that Look in is set to the working directory.

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3. Leave Directory empty.

To save the surface files to a different directory, you could enter that directory name under Directory, or elseyou could browse to that directory so that it appears under Look in.

4. Leave Base Filename empty.

To give the surface file names a common prefix, you could enter a prefix under Base Filename.

5. Click Choose.

Four files are saved to the working directory:

DescriptionFile Name

Low-Theta periodic surfaceBlade_1_LP.crv

Interface between Blade 1 and Deformed BladeBlade_1_Deformed_Blade_interface.crv

Interface between Deformed Blade and Blade 3Deformed_Blade_Blade_3_interface.crv

High-Theta periodic surfaceBlade_3_HP.crv

Saving the Inlet and Outlet LocationsSave the inlet and outlet locations for later use:

1. Click File > Save > Inlet.

The Save Inlet dialog box appears.

2. Set File name to inlet and click Save.

The inlet points are written to a file named inlet.crv.

3. Click File > Save > Outlet.

4. Set File name to outlet and click Save.

The outlet points are written to a file named outlet.crv.

Defining the Topology for the Deformed Blade GroupApply an H/J/C/L-Grid topology to force ANSYS TurboGrid to set the specific topology type automatically for theupstream and downstream halves of each blade:

1. Open Topology Set.

2. Set Topology Definition > Method to H/J/C/L-Grid.

3. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

4. Set Include O-Grid > Width Factor to 0.25.

This will specify the O-Grid thickness to be approximately equal to 25% of the average blade width. This valueis smaller than the default value of 0.5 because of the relatively short distance between the blades, comparedto the blade thickness, at the hub.

5. Leave the One-to-one Interface Ranges settings set to Full.

These settings force the periodic interface and the passage interfaces to use one-to-one node connections. Thealternative is to use a GGI (General Grid Interface) connection, or a combination of GGI and one-to-oneconnections. GGI connections allow more freedom when adjusting a mesh, but can potentially reduce theaccuracy of CFD results.

6. Set Periodicity > Projection to Float on Curves.

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This setting forces the periodic surfaces of the topology (and ultimately the mesh) to lie on the periodic surfacesthat were defined as part of the geometry. This constraint is necessary to ensure that the mesh you are currentlymaking will fit properly with the mesh you will make later in this tutorial.

The default setting, Float on Surface, is not suitable in this case, since it allows the periodic surfacesof the topology to deviate from the geometric periodic surfaces as a way of improving mesh quality.

7. Click Apply to set the topology.

8. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

9. Click Freeze to freeze the topology settings.

This completes the topology definition.

Reviewing the Mesh Data Settings for the Deformed BladeGroup

Leave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.In accordance with the problem description, you will increase the mesh density later in this tutorial. Leaving themesh density coarse in the meantime will reduce processing time while you adjust the topology.

As prescribed in the problem description, the mesh should contain an inlet domain and an outlet domain. For now,leave the Inlet Domain and Outlet Domain check boxes cleared; you will select these check boxes later in thistutorial. Omitting the inlet and outlet domains in the meantime will reduce the processing time while you adjust thetopology.

Reviewing the Mesh Quality on the Hub and Shroud Tip Layersof the Deformed Blade Group

The Layers > Hub and Layers > Shroud Tip objects are colored red in the tree view, indicating that thereare problems with mesh quality that should be resolved.

Modifying the Hub LayerView the Hub layer:

1. Right-click a blank area in the viewer, and select Transformation > Blade-to-Blade (Theta-M') from theshortcut menu.

2. Click Hide all geometry objects .

3. Turn off the visibility of Layers > Shroud Tip.

4. Click Fit View .

View the problem areas of the Hub layer:

1. Open Layers > Hub.

The object editor shows mesh measures, such as Minimum Face Angle, for all 2D elements in the surfacemesh on the layer.

2. Double-click Minimum Face Angle.

The problem areas of the mesh are colored red in the viewer.

3. Double-click Maximum Face Angle.

The problem areas of the mesh are colored red in the viewer.

Improve the topology distribution on the Hub layer:

• Move master control points as shown in Hub Layer Changes (p. 81).

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After each change, you can update the display of problem areas in the mesh by double-clicking MinimumFace Angle and Maximum Face Angle.

Figure 9.4. Hub Layer Changes

Modifying the Shroud Tip LayerView the Shroud Tip layer:

1. Turn off the visibility of Layers > Hub.

2. Turn on the visibility of Layers > Shroud Tip.

3. Click Fit View .

View the problem areas of the Shroud Tip layer:

1. Open Layers > Shroud Tip.

2. Double-click Minimum Face Angle.

The problem areas of the mesh are colored red in the viewer.

3. Double-click Maximum Face Angle.

The problem areas of the mesh are colored red in the viewer.

Improve the topology distribution on the Shroud Tip layer:

1. Move master control points as shown in Shroud Tip Layer Changes - Control Point Movements (p. 82).

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Figure 9.5. Shroud Tip Layer Changes - Control Point Movements

2. Add a master control point at the location shown in Shroud Tip Layer Changes - New Control Point (p. 83):

1. Right-click the location where the new control point is to be added.

2. Select Control Point > Insert Master.

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Figure 9.6. Shroud Tip Layer Changes - New Control Point

3. Restrict the freedom of movement of the added control point to movement along the O-Grid curve:

1. Open Layers.

2. On the Advanced Parameters tab, set Leading And Trailing Edge O-Grid Control Points > Methodto Curve.

3. Click Apply.

4. Move the control point as indicated in Shroud Tip Layer Changes - New Control Point (p. 83).

If the movement of the control point were much larger, the mesh density in front of the blade would need tobe increased. In such a situation, you could use an edge split control to locally increase the mesh density.

5. Improve mesh orthogonality near the deformed blade by adding and moving a master control point, and movinganother control point, as shown in Shroud Tip Layer Changes - A Second New Control Point (p. 84).

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Figure 9.7. Shroud Tip Layer Changes - A Second New Control Point

Increasing the Mesh Density for the Deformed Blade GroupAs stated in the problem description, the mesh requires a density of about 250000 nodes per blade. Increase themesh density. Also add inlet and outlet blocks as prescribed in the problem description:

1. Open Mesh Data.

2. Enter the following settings for Mesh Data:

ValueSettingTab

Target Passage Mesh SizeMethodMesh Size

SpecifyNode Count

750000Target

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ValueSettingTab

(Selected)Inlet Domain

(Selected)Outlet Domain

3. Click Apply.

As a result of choosing the mesh size in the previous step, ANSYS TurboGrid has re-calculated the number ofelements along various topological paths. In order to provide higher mesh resolution near the walls, set the size formesh elements touching the hub, blade, shroud tip, and shroud to a “y+” value of 1. These changes can cause themesh density to become too sparse in some locations. In this case, the density across the O-Grid would be too sparseif left unchanged. To compensate, increase the number of elements across the O-Grid from 9 to 18.

1. Enter the following settings for Mesh Data:

ValueSettingTab

y+Near Wall Element Size Specification > MethodMeshSize

1.0e6Reynolds No.

Element Count and SizeSpanwise Blade Distribution Parameters > MethodPassage

66Spanwise Blade Distribution Parameters > # of Elements

33Spanwise Blade Distribution Parameters > Const Element

1Spanwise Blade Distribution Parameters > Size of Elements Next to Wall(y+) > Hub

(Selected)Apply O-Grid Parameters To All Blades

Element Count and SizeApply O-Grid Parameters To All Blades > Method

18Apply O-Grid Parameters To All Blades > # of Elements

1Apply O-Grid Parameters To All Blades > Size of Elements Next to Wall(y+ ) > Blade

Element Count and SizeShroud Tip Distribution Parameters > MethodShroudTip

8Shroud Tip Distribution Parameters > # of Elements

0Shroud Tip Distribution Parameters > Const Element

1Size of Elements Next to Wall (y+) > Tip

1Size of Elements Next to Wall (y+) > Shroud

2. Click Apply.

At the interface between the passage and the inlet domain, spanwise node alignment is adversely affected by thehigh curvature of the leading edge of the deformed blade. To improve this node alignment, change a certain settingthat affects the spanwise distribution of nodes in the passage mesh:

1. Right-click Mesh Data and click Edit in Command Editor.

2. Change Mesh Generation from false to Constant Span.

3. Click Process to apply the changes.

4. Click Close.

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Revisiting the Mesh Quality on the Hub and Shroud Tip Layersof the Deformed Blade Group

After changing the mesh size, it is possible for the mesh quality to change. You can quickly confirm that the faceangles are acceptable by verifying that all layers are shown in black text in the tree view. To see the exact valuesof the minimum and maximum face angles, open each layer in the object editor:

1. Open Layers > Hub.

2. Confirm that the mesh measures are acceptable.

It is normal for the aspect ratio of the elements next to the blade to be very high.

3. Open Layers > Shroud Tip.

4. Confirm that the mesh measures are acceptable.

Generating the Mesh for the Deformed Blade GroupNow that the topology has been defined and the mesh quality is acceptable on all layers, generate the mesh:

• Click Insert > Mesh.

Analyzing the Mesh for the Deformed Blade GroupIn the process of generating the mesh, ANSYS TurboGrid automatically added new layers as required to guide themesh in the spanwise direction. Verify the mesh quality for the added layers by checking that each layer is listedin black text in the tree view.

Mesh statistics for the 3D mesh elements are available now that the mesh has been created. Inspect the mesh qualityof the 3D mesh:

1. Open Mesh Analysis.

Opening either of these objects causes the Mesh Statistics dialog box to appear. This dialog box shows meshmeasures for all 3D elements in the mesh.

2. Confirm that the mesh measures are acceptable.

You can expect higher element volume ratios near the blade, hub, and shroud, where expansion rates in multipledirections multiply to increase the volume ratio between elements that share a node.

You can expect high edge length ratios near the walls because the requirement to place the first nodes fromthe walls at y+ = 1 causes the elements next to the walls to be highly compressed in one direction.

3. On the Mesh Statistics dialog box, click Close.

Saving the Mesh for the Deformed Blade GroupSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to DeformedSection.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State for the Deformed Blade Group (Optional)If you want to revisit this mesh at a later date, save the state:

1. Select File > Save State As.

2. Enter an appropriate state file name.

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3. Click Save.

Mesh for an Undeformed BladeIn this part of the tutorial you will create a mesh for one undeformed turbine blade. Multiple instances of this meshcould be used, in conjunction with the mesh you made earlier, to simulate the entire blade row.

Starting a New CaseStart a new case:

• Click File > New Case.

If you chose not to save the state for the previous mesh, a dialog box will appear asking if you want to save thestate. In this case, click Save & Proceed or Proceed as appropriate.

Defining the Geometry for the Undeformed BladeYou must use the same periodic surfaces in meshes that are intended to fit together along the same blade row. Inthe mesh you made earlier, the deformed blade might have affected the shape of the periodic surface, even thoughthe deformed blade is between undeformed blades. The only way to guarantee that the same periodic surface is usedin the present mesh is to load the periodic surface from the previous mesh.

You must use the same inlet and outlet surfaces in meshes that are intended to fit together along the same bladerow. Since you have modified the inlet and outlet surfaces in the process of making the previous mesh, you mustload them for the present mesh. Even if you had not modified the inlet and outlet surfaces, the deformed blade mighthave influenced the initial shape of the inlet and outlet surfaces.

Define the geometry using the periodic surfaces and inlet and outlet curves that you saved earlier:

1. Click File > Load BladeGen.

2. Open BladeGen.inf from the working directory.

3. Use the same file, Blade_1_LP.crv, to define both periodic surfaces, and apply a (360/71)° rotation forthe high periodic surface:

1. Open Geometry > Low Periodic.

2. Enter the following settings for Low Periodic:

ValueSettingTab

From FileMethodData

Blade_1_LP.crvFile Name

0 [degree]Rotation Angle

3. Click Apply.

4. Open Geometry > High Periodic.

5. Enter the following settings for High Periodic:

ValueSettingTab

From FileMethodData

Blade_1_LP.crvFile Namea

5.070423 [degree]Rotation Angle

aUse the same file as for the low periodic surface.

6. Click Apply.

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4. Load the inlet and outlet curve files inlet.crv and outlet.crv:

1. Right-click a blank area in the viewer, and click Transformation > Meridional (A-R) from the shortcutmenu so that you can better see the effect of loading the inlet and outlet curve files.

2. Open Geometry > Inlet.

3. Click Read from File .

The Open Inlet File dialog box appears.

4. Select inlet.crv.

5. Click Open.

6. Open Geometry > Outlet and load outlet.crv in the same way.

Adding a Shroud TipAs stated in the problem description, the blade set requires a blade tip clearance of 0.05 cm at the shroud. Add thisclearance by editing the Shroud Tip object:

1. Open Geometry > Blade Set > Shroud Tip.

2. Enter the following settings for Shroud Tip:

ValueSettingTab

Normal DistanceClearance Type > Tip OptionShroud Tip

0.05 [cm]Clearance Parameter > Tip Clearance

3. Click Apply.

Defining the Topology for the Undeformed BladeApply an H/J/C/L-Grid topology to force ANSYS TurboGrid to set the specific topology type automatically for theupstream and downstream halves of the blade:

1. Right-click a blank area in the viewer, and select Transformation > Blade-to-Blade (Theta-M') from theshortcut menu.

2. Open Topology Set.

3. Set Topology Definition > Method to H/J/C/L-Grid.

4. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

5. Set Include O-Grid > Width Factor to 0.25.

This will specify the O-Grid thickness to be approximately equal to 25% of the average blade width. This valueis smaller than the default value of 0.5 because of the relatively short distance between the blades, comparedto the blade thickness, at the hub.

6. Click Apply.

Constrain the topology so that the resulting mesh has periodic surfaces that fall exactly on the geometric periodicsurfaces. This will ensure that the periodic surfaces of the present mesh will fit with those of the mesh you createdearlier for the deformed blade group.

1. Set Periodicity > Projection to Float on Curves.

2. Click Apply to set the topology.

3. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology is generated.

4. Click Freeze to freeze the topology settings.

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This completes the topology definition.

Reviewing the Mesh Data Settings for the Undeformed BladeLeave the Mesh Data settings at their default values. The target number of nodes is set to produce a coarse mesh.In accordance with the problem description, you will increase the mesh density later in this tutorial. Leaving themesh density coarse in the meantime will reduce processing time while you adjust the topology.

As prescribed in the problem description, the mesh should contain an inlet domain and an outlet domain. For now,leave the Inlet Domain and Outlet Domain check boxes cleared; you will select these check boxes later in thistutorial. Omitting the inlet and outlet domains in the meantime will reduce the processing time while you adjust thetopology.

Reviewing the Mesh Quality on the Hub and Shroud Tip Layersof the Undeformed Blade

The Layers > Hub object is colored red in the tree view, indicating that there are problems with mesh quality thatshould be resolved.

Modifying the Hub LayerView the Hub layer:

1. Click Hide all geometry objects .

2. Turn off the visibility of Layers > Shroud Tip.

3. Click Fit View .

View the problem areas of the Hub layer:

1. Open Layers > Hub.

2. Double-click Minimum Face Angle.

The problem areas of the mesh are colored red in the viewer.

3. Double-click Maximum Face Angle.

The problem areas of the mesh are colored red in the viewer.

Improve the topology distribution on the Hub layer:

• Move master control points as shown in Hub Layer Changes (p. 90).

After each change, you can update the display of problem areas in the mesh by double-clicking MinimumFace Angle and Maximum Face Angle.

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Figure 9.8. Hub Layer Changes

Increasing the Mesh Density for the Undeformed BladeAs stated in the problem description, the mesh requires a density of about 250000 nodes per blade. Increase themesh density. Also add inlet and outlet blocks as prescribed in the problem description:

1. Open Mesh Data.

2. Enter the following settings for Mesh Data:

ValueSettingTab

Target Passage NodesMethodMesh Size

SpecifyNode Count

250000Target

(Selected)Inlet Domain

(Selected)Outlet Domain

3. Click Apply.

To further improve similarity with the mesh for the deformed blade group, use the same “y+” values and elementcounts as for that mesh:

1. Enter the following settings for Mesh Data:

ValueSettingTab

y+Near Wall Element Size Specification > MethodMeshSize

1.0e6Reynolds No.

Element Count and SizeSpanwise Blade Distribution Parameters > MethodPassage

66Spanwise Blade Distribution Parameters > # of Elements

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ValueSettingTab

33Spanwise Blade Distribution Parameters > Const Element

1Spanwise Blade Distribution Parameters > Size of Elements Next to Wall(y+) > Hub

Element Count and SizeO-Grid > Method

18O-Grid > # of Elements

1O-Grid > Size of Elements Next to Wall (y+) > Blade

Element Count and SizeShroud Tip Distribution Parameters > MethodShroudTip

8Shroud Tip Distribution Parameters > # of Elements

0Shroud Tip Distribution Parameters > Const Element

1Size of Elements Next to Wall (y+) > Tip

1Size of Elements Next to Wall (y+) > Shroud

2. Click Apply.

Revisiting the Mesh Quality on the Hub and Shroud Tip Layersof the Undeformed Blade

After changing the mesh size, it is possible for the mesh quality to change. You can quickly confirm that the faceangles are acceptable by verifying that all layers are shown in black text in the tree view. To see the exact valuesof the minimum and maximum face angles, open each layer in the object editor:

1. Open Layers > Hub.

2. Confirm that the mesh measures are acceptable.

3. Open Layers > Shroud Tip.

4. Confirm that the mesh measures are acceptable.

Generating the Mesh for the Undeformed BladeCreate the mesh:

• Click Insert > Mesh.

Analyzing the Mesh for the Undeformed BladeVerify the mesh quality for the added layers by checking that each layer is listed in black text in the tree view.

Inspect the mesh quality of the 3D mesh:

1. Open Mesh Analysis.

2. Confirm that the mesh measures are acceptable.

3. On the Mesh Statistics dialog box, click Close.

Saving the Mesh for the Undeformed BladeSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to cm.

4. Set File name to UndeformedSection.gtm.

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5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State for the Undeformed Blade (Optional)If you want to revisit this mesh at a later date, save the state:

1. Select File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

SummaryIn this tutorial, you created two meshes for modeling an axial turbine blade row with one deformed blade. The firstmesh, DeformedSection.gtm, models one deformed blade between a pair of undeformed blades. The secondmesh, UndeformedSection.gtm, models one undeformed blade.

The complete blade row contains 71 blades. To model the complete blade row using CFX-Pre, you could begin anew simulation using Turbo mode to define a set of 68 blades based on UndeformedSection.gtm, then youcould enter General mode and add DeformedSection.gtm.

This technique for modeling a single deformed blade can be extended to model multiple deformed blades by creatinga larger blade group for the deformed section.

Further ExerciseAs a further exercise, you can try creating single-blade meshes for each blade in the blade group. You can do thisby creating a mesh for a single blade, using the Blade_1_Deformed_Blade_interface.crv andDeformed_Blade_Blade_3_interface.crv files for the periodic surfaces as appropriate. This arrangementallows you to modify the mesh for the deformed blade without involving other blades.

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Saving the State for the Undeformed Blade (Optional)

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Chapter 10. Francis TurbineThis tutorial includes:

• Before You Begin (p. 94)

• Starting ANSYS TurboGrid (p. 94)

• Defining the Geometry (p. 94)

• Defining the Topology (p. 96)

• Reviewing the Mesh Quality on the Hub and Shroud Layers (p. 97)

• Specifying Mesh Data Settings (p. 101)

• Generating the Mesh (p. 102)

• Analyzing the Mesh (p. 102)

• Saving the Mesh (p. 103)

• Saving the State (Optional) (p. 103)

This tutorial teaches you how to:

• Deal with a stepped hub.

• Use an L-Grid topology.

• Use edge split controls to increase the mesh density at specific locations.

As you work through this tutorial, you will create a mesh for a blade passage of a Francis water turbine. A typicalblade passage is shown by the black outline in the figure below.

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The turbine contains 13 blades that revolve about the X-axis. Within the blade passage, the maximum diameter ofthe shroud is approximately 4.23 m.

The mesh density should be set appropriately for using the SST turbulence model in a CFD simulation.

Before You BeginIf this is your first tutorial, review the topics in Introduction to the ANSYS TurboGrid Tutorials (p. 1).

Starting ANSYS TurboGrid1. Prepare the working directory using the files in the examples/francis directory.

For details, see Preparing a Working Directory (p. 1).

2. Set the working directory and start ANSYS TurboGrid.

For details, see Setting the Working Directory and Starting ANSYS TurboGrid (p. 1).

Defining the GeometryLoad the geometry and view it in the meridional view:

1. Open the BladeGen.inf file.

2. Right-click a blank area in the viewer, and click Transformation > Meridional (A-R) from the shortcut menu.

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Before You Begin

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Note the discontinuity in the hub geometry. In order to capture this discontinuity in the final mesh, the backgroundmesh on which it is based must also capture the discontinuity. The background mesh is an internal mechanism thatANSYS TurboGrid uses to represent the geometry. It is based on the original curve files and other geometry settings,and is used to generate the topology and ultimately the CFD mesh. In general, if you have a step change or otherdiscontinuity in the hub, shroud, or blade, you should try increasing the resolution of the background mesh. Thegoal is to line up a node of the background mesh with the point at which the discontinuity occurs. By increasingthe background mesh density, the probability increases that a background mesh node will exist within a tolerabledistance of the discontinuity. If the (CFD) mesh does not adequately follow the geometry (even with sufficiently-highCFD mesh resolution), then increase the background mesh density further.

Increase the resolution of the background mesh:

1. Right-click Geometry > Machine Data and click Edit in Command Editor.

2. Change Turbo Transform Background Mesh Size For Topology from 2000 to 80000.

3. Click Process to apply the changes.

4. Click Close.

Adjusting the Outlet PointsAs can be seen in the viewer, the white diamonds that define the outlet curve are not at a uniform distance from thetrailing edge of the blade. In particular, the low hub point is much closer to the blade than the other points of theoutlet curve.

Move the outlet point on the hub farther away from the blade, and the outlet point on the shroud closer to the blade,as follows:

1. Open Geometry > Outlet.

2. Under List of Points, select Low Hub Point.

3. Set Method to Set R and Location to 0.50.

4. Click Apply.

5. Under List of Points, select Low Shroud Point.

6. Set Method to Set A and Location to 1.75.

7. Click Apply.

8. Click Generate Intermediate Points .

9. A message box warns you that the intermediate points will be deleted. Click Yes to delete the existingintermediate points and replace them with new ones.

Looking at the intermediate point distribution in the viewer, you can see that adding more points would significantlyimprove the smoothness of the curve. Add two more points to Geometry > Outlet using one of the followingprocedures:

• If there are currently four intermediate points:

1. Under Curve, right-click Point 3 in the list and click New from the shortcut menu.

Alternatively, select Point 3 then, beside the list of points, click New .

2. Select the newly-added point, point 5, and set its location to (1.51, 1.10) so that it is at about the samedistance from the trailing edge as the other points.

These coordinates were originally determined by moving point 5 using the mouse.

3. Click Apply.

4. Right-click Point 4 in the list and click New from the shortcut menu.

5. Set the location of the newly created point, point 6, to (1.73, 1.73) and click Apply.

• If there are currently three intermediate points:

1. Under Curve, right-click Point 2 in the list and click New from the shortcut menu.

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Adjusting the Outlet Points

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Alternatively, select Point 2 then, beside the list of points, click New .

2. Select the newly-added point, point 4, and set its location to (1.51, 1.10) so that it is at about the samedistance from the trailing edge as the other points.

These coordinates were originally determined by moving point 4 using the mouse.

3. Click Apply.

4. Right-click Point 3 in the list and click New from the shortcut menu.

5. Set the location of the newly created point, point 5, to (1.73, 1.73) and click Apply.

Before continuing, ensure that the outlet points are on a relatively smooth curve at a uniform distance from theblade.

Defining the TopologyApply an H/J/C/L-Grid topology to force ANSYS TurboGrid to set the specific topology type automatically for theupstream and downstream halves of the blade:

1. Right-click a blank area in the viewer, and click Transformation > Cartesian (X-Y-Z) from the shortcutmenu.

2. Open Topology Set.

3. Set Topology Definition > Method to H/J/C/L-Grid.

4. Ensure that Include O-Grid is selected.

This adds an O-Grid around the blade to increase mesh orthogonality in that region.

5. Set Include O-Grid > Width Factor to 0.4.

This slight reduction in O-Grid width is needed due to the small passage width near the trailing edge of theblade at the hub.

6. Set One-to-one Interface Ranges > Periodic to Between Blades & Upstream.

The high blade stagger angle in the downstream end of the passage makes the J-Grid and L-Grid topologiesgood candidates for the downstream end of the passage. In order to make an L-Grid topology possible in thedownstream end, there must not be one-to-one node periodicity along the periodic interface in that end of thepassage.

7. Leave Periodicity > Projection set to Float on Surface.

This allows the periodic surface of the mesh to deviate from the geometric periodic surface, in order to improvemesh skewness properties along the periodic boundary. The topology on a given layer floats on the layer, butis not constrained to stop exactly on the intersection of the layer with the geometric periodic surface.

8. Click Apply.

9. Right-click Topology Set and turn off Suspend Object Updates.

After a short time, the topology appears.

10. Open Topology Set > Blade 1.

11. On the Advanced Parameters tab, confirm that H/J/C/L Topology Definition > Trailing Edge is set toL-Grid.

12. On the same tab, confirm that Override Sharp TE Determination > Sharp Trailing Edge is selected.

13. Click Freeze to freeze the topology settings.

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Defining the Topology

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Reviewing the Mesh Quality on the Hub and ShroudLayers

The Layers > Hub and Layers > Shroud objects are shown in red text in the object selector.

Modifying the Hub LayerThe Layers > Hub object is colored red in the tree view, indicating that there are problems with mesh quality thatshould be resolved.

View the Hub layer:

1. Right-click a blank area in the viewer, and click Transformation > Blade-to-Blade (Theta-M') from theshortcut menu.

2. Click Hide all geometry objects .

3. Turn off the visibility of Layers > Shroud.

4. Turn on the visibility of Layers > Hub.

5. Click Fit View .

View the problem areas of the Hub layer:

1. Open Layers > Hub.

2. Double-click Minimum Face Angle.

The problem areas of the mesh are colored red in the viewer.

3. Double-click Maximum Face Angle.

The problem areas of the mesh are colored red in the viewer.

Improve the topology distribution on the Hub layer:

1. Insert a master control point and move it as shown in Hub Layer Changes in Downstream End (p. 98):

1. Right-click the location where the new control point is to be added.

2. Select Control Point > Insert Master.

A yellow master control point should appear. If the master control point is colored magenta, it will appearat the intersection of two red lines. In that case, delete the added point, then right-click where one of thosered lines intersected the master topology line and again select Control Point > Insert Master.

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Figure 10.1. Hub Layer Changes in Downstream End

2. Move a master control point as shown in Hub Layer Changes in Upstream End (p. 99).

The minimum face angle should now be approximately 35°.

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Modifying the Hub Layer

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Figure 10.2. Hub Layer Changes in Upstream End

3. For better mesh resolution along the periodic interface, use an edge split control to double the mesh density atthe lower location indicated in Increasing Mesh Density Locally (p. 100):

1. Right-click the master topology line marked “A” in Figure 10.3, “Increasing Mesh Density Locally” (p. 100)and select Insert Edge Split Control from the shortcut menu.

2. In the object editor, change Split Factor to 2.0.

3. Click Apply.

This causes more elements to be placed along the topology line marked “A” in the figure.

Note that edge split controls act on all layers.

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Modifying the Hub Layer

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Figure 10.3. Increasing Mesh Density Locally

4. In order to reduce the aspect ratio of mesh elements downstream of the blade, use edge split controls to doublethe mesh density along the topology lines marked “B” and “C” in Increasing Mesh Density Locally (p. 100).

Modifying the Shroud LayerThe Layers > Shroud object is colored red in the tree view, indicating that there are problems with mesh qualitythat should be resolved.

View the Shroud layer:

1. Turn off the visibility of Layers > Hub.

2. Turn on the visibility of Layers > Shroud.

3. Click Fit View .

View the problem areas of the Shroud layer:

1. Open Layers > Shroud.

2. Double-click Minimum Face Angle.

The problem areas of the mesh are colored red in the viewer.

3. Double-click Maximum Face Angle.

The problem areas of the mesh are colored red in the viewer.

Improve the topology distribution on the Shroud layer:

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Modifying the Shroud Layer

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• Move master control points as shown in Shroud Layer Changes (p. 101).

After each change, you can update the display of problem areas in the mesh by double-clicking MinimumFace Angle and Maximum Face Angle.

Moving the right-most control point will not improve the mesh immediately, but will avoid small minimumface angles when a mesh is generated later on in the tutorial.

Figure 10.4. Shroud Layer Changes

Specifying Mesh Data Settings• In anticipation of using the SST turbulence model, increase the mesh density and set the near-wall y+ values

for the hub, shroud, and blade to 1. Also add an outlet block and set its mesh type to H-Grid inParametric Space in order to better capture the change in radius of the hub in the outlet region.

1. Open Mesh Data.

2. Enter the following settings for Mesh Data.

ValueSettingTab

Target Passage Mesh SizeMethodMesh Size

SpecifyNode Count

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Specifying Mesh Data Settings

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ValueSettingTab

750000Target

y+Near Wall Element Size Specification > Method

(Selected)Outlet Domain

Element Count and SizeSpanwise Blade Distribution Parameters > MethodPassage

80Spanwise Blade Distribution Parameters > # of Elements

25Spanwise Blade Distribution Parameters > Const Elements

1Spanwise Blade Distribution Parameters > Size of ElementsNext to Wall (y+) > Hub

1Spanwise Blade Distribution Parameters > Size of ElementsNext to Wall (y+) > Shroud

Element Count and SizeO-Grid > Method

20O-Grid > # of Elements

1O-Grid > Size of Elements Next to Wall (y+) > Blade

H-Grid in Parametric SpaceOutlet Domain > Mesh TypeInlet/Outlet

(Selected)Outlet Domain > Override default # of Elements

30Outlet Domain > Override default # of Elements > # ofElements

In order to set the y+ value on the hub and shroud, you could use either the Element Count andSize method or the Boundary Layer method. In this case, the Element Count and Sizeoption was arbitrarily chosen. As a result, the number of elements from hub to shroud, and the numberof constant-size elements in the middle section (away from the hub and shroud) were required. The valuesgiven here were found, by trail and error, to produce a good mesh.

Similarly, to set the y+ value on the blade, you could use either the Element Count and Sizemethod or the Expansion Rate method. The Element Count and Size method was arbitrarilychosen. As a result, the number of elements across the O-Grid was required. The value given here wasfound, by trail and error, to produce a good mesh.

The number of elements in the outlet domain and in the O-Grid were changed to values that were found,by trail and error, to produce a good mesh.

3. Click Apply.

Generating the MeshCreate the mesh:

• Click Insert > Mesh.

Analyzing the MeshInspect the mesh quality of the 3D mesh:

1. Open Mesh Analysis.

2. Confirm that the mesh measures are acceptable.

3. On the Mesh Statistics dialog box, click Close.

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Generating the Mesh

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Saving the MeshSave the mesh:

1. Click File > Save Mesh As.

2. Ensure that File type is set to ANSYS CFX.

3. Set Export Units to m.

4. Set File name to FrancisTurbine.gtm.

5. Ensure that your working directory is set correctly.

6. Click Save.

Saving the State (Optional)If you want to revisit this mesh at a later date, save the state:

1. Select File > Save State As.

2. Enter an appropriate state file name.

3. Click Save.

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Saving the Mesh

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