AM-Intro 13.0 L02 Meshing Methods

Customer Training Material

L t 2Lecture 2

Meshing Methodsg

Introduction to ANSYSIntroduction to ANSYS Meshing

L2-1ANSYS, Inc. Proprietary© 2011 ANSYS, Inc. All rights reserved.

Release 13.0February 2011

Introduction to ANSYS Meshing

Customer Training MaterialMeshing Methods

What you will learn from this presentation

Automatic Meshing

Algorithms for Tetrahedral Meshing

Different methods for Hex MeshingDifferent methods for Hex Meshing

CutCell meshing

Meshing for 2D and shell analysisg y

New Features:• Direct Meshing

P t i ti i ANSYS M hi• Parameterization in ANSYS Meshing

• Extended Meshing




Customer Training MaterialPreprocessing Workflow

Geometry Creation

OR Geometry Import

Geometry Operations Meshing Solver

Sketches and Planes 3D Operations Meshing

Methodsa es

3D Operations

Extrude, Revolve, Sweep etc

Boolean, Body Operations, Split,

etc

Hybrid Mesh: Tet, Prisms, Pyramids

Hexa Dominant, Sweep meshing

Geometry Import Options

Geometry Cleanup and

Repair

Automatic Cleanup

Sweep, etc Sweep meshing

Global Mesh

CutCell meshing

Direct CAD/Bi-Directional CAD

Cleanup

Merge, Connect, Projection, Flow

Volume Extraction, etc

Settings

Local Mesh Settings

Sizing,



gBody/Sphere of Influence, Match

Control, etc


Customer Training MaterialMeshing Process in ANSYS Meshing




Customer Training MaterialMeshing Methods• Meshing Methods available for 3D bodies

– Automatic– Tetrahedrons

• Patch Conforming• Patch Independent

– MultiZone• Mainly hexahedral elements

– Hex dominant– Sweep– CutCell

• Meshing Methods available for 2D bodiesA t ti M th d (Q d D i t)– Automatic Method (Quad Dominant)

– Triangles– Uniform Quad/Tri

U if Q dTriangle (Tri) Quadrilateral (Quad)



– Uniform Quad



Automatic Meshing Methodg




Customer Training MaterialAutomatic Meshing Method• The Automatic setting toggles between Tetrahedral (Patch Conforming)

and Swept Meshing, depending upon whether the body is sweepable. Bodies in the same part will have a conformal mesh

Patch Conforming Mesh

S ept Meshing



Swept Meshing



Tetrahedron/hybrid Meshingy g




Customer Training MaterialMeshing Methods: Tetrahedron• Generates tetrahedral elements• Two algorithms are available:

– Patch Conforming (TGrid)g ( )– Patch Independent (ICEM CFD)

Patch Conforming Mesh Patch Independent Mesh



Patch Conforming Mesh Patch Independent Mesh


Customer Training MaterialTetrahedron Meshing Algorithms• Patch Conforming:

– Bottom up approach : Meshing process starts from edge, face and then body– All faces and their boundaries are respected and meshed– Good for clean CAD geometries

• Patch Independent: – Top down approach : The volume mesh is generated first, and this is projected p pp g , p j

on to faces and edges to create the surface mesh– The faces and their boundaries (edges and vertices) are not necessarily

respected if they fall under a specified tolerance, unless, there is a named l ti l d b d diti th bj t d t thselection, load, boundary condition or other object scoped to them

– Good for gross de-featuring of dirty CAD geometries• Both tetrahedron meshing algorithms can be applied to the parts, bodies

d ltib d t N i AM 13 0!N i AM 13 0!and multibody parts New in AM 13.0!New in AM 13.0!

• Both tetrahedron meshing algorithms can be inflated for boundary layer resolution often required for CFD




Customer Training MaterialTetrahedron Meshing: Patch Conforming Method

• Right click on Mesh and insert a Method• Select the body(s) to which the method is to be

applied• Set the Method to Tetrahedrons and the

Algorithm to Patch Conforming• Different parts and bodies can have different p

methods New in AM 13.0!New in AM 13.0!• Surface mesh is generated first which by default

respects the boundaries of all faces and edges p gin the geometry and the volume mesh is created from the surface mesh

• Mesh does not depend on any loads, boundary

Faces in close proximity

p y , yconditions, Named Selections or results scoped to the bodies




Customer Training MaterialTetrahedron Meshing: Patch Conforming Method

Example:

Faces, edges and proximities are respected and resolved




Customer Training MaterialTetrahedron Meshing: Patch Independent Method

• Handy for dirty CAD with sliver faces, short edges, poor surface parameterization, etc.

• With the Method to Tetrahedrons, set the Algorithm to Patch Independent

• The boundaries of faces and edges will not be respected unless there is a ‘Named Selection’, load, boundary condition or other object scoped to them

• Note that there are additional settings for mesh de-featuring and also refinement settings based on curvature and proximity

• Possible to set different curvature and proximity settings for different bodies

• Additional Smooth Transition option New in AM 13.0!New in AM 13.0!• Possible to control the growth rate and the feature

angle locally New in AM 13.0!New in AM 13.0!



g y• Ability to write ICEM CFD files New in AM 13.0!New in AM 13.0!



Example: 1

Face and edges under th d l ti

Without Named selections, faces and

edges are not respected the named selection for this method are respected

Define Named Selections before grid generation process

Faces and edges under named selections are

respected





Example: 2

Set Mesh Based Defeaturing to On and enter a value for the Defeaturing Toleranceg

Geometry No Defeaturing Defeaturing Tolerance of 0.1





Example: 3

Effect of Curvature and Proximity Refinement

C t d P i it R fi t Y (d f lt) C t d P i it R fi t NCurvature and Proximity Refinement Yes (default) Curvature and Proximity Refinement No





Example: 4

Effect of Smooth Transition New in AM 13.0!New in AM 13.0!Smooth transition uses advanced frontSmooth transition uses advanced front meshing technique

S th T iti Off (d f lt) S th T iti OSmooth Transition Off (default) Smooth Transition On




Customer Training MaterialTetrahedron Meshing with Inflation• Can be referred to as Prism Layers. Generally needed to :

– Resolve high gradients of flow variables and physics complexities in close vicinity of walls for CFD analysis

– Resolve thin air gaps in Electromagnetic analysis– Resolve regions of high stress concentrations in Mechanical analysis

• Inflation layers can be generated from Tri and Quad surface mesh• Inflation can be grown both with Patch Conforming as well as Patch

Independent tetrahedron meshing methods• Inflation can be applied using ‘global’ mesh settings as well as using pp g g g g

‘Local’ mesh settings



Inflation preview Tet + Prisms


Customer Training MaterialVirtual TopologyWhen to use?• To merge together a number of small (connected)

faces/edges• To simplify small features in the model• To simplify load abstraction for mechanical analysis• To create edge splits for better control of the surface• To create edge splits for better control of the surface

mesh New In AM 13.0!New In AM 13.0!

• Virtual cell modifies the topology– Original CAD model remains unchanged

New faceted geometry is created with virtual topology– New faceted geometry is created with virtual topology




Customer Training MaterialVirtual Topology : Example

Without Virtual cells:

Edges are respected while g pcreating surface mesh

With Virtual cells:

Small faces are merged to form a single virtual face and edges of thesingle virtual face and edges of the original set of faces are no longer respected for meshing

Creating virtual topologies• RMB on Model tree and select Insert Virtual Topologyselect Insert Virtual Topology• Select Virtual Topology from the Tree Outline• Pick faces or edges, RMB



gand Insert Virtual Cell


Customer Training MaterialVirtual Topology : ExampleCreating edge split New in AM 13.0!New in AM 13.0!• Select Virtual Topology from the Tree Outline• Pick the edge(s)• RMB and select ‘Virtual Split Edge at +’ or ‘Virtual Split

Edge’ to split the edge at the location specified by the selection, or to enter the split ratio in the Details window respectivelywindow, respectively

With edge splits:

We can add edge constrains to improve the mesh



g p

Edge splits can be moved interactively. Pick the virtual edge, hold the F4 key and move the red node along the edge with the mouse



Hex/Hex Dominant Meshingg




Customer Training MaterialIntroduction• Hex/Hex Dominant Meshing

– Reduced element count• Faster convergence

Elements aligned in direction of flow– Elements aligned in direction of flow• Improved Accuracy

– Reduced numerical error

Tet Mesh

Elements: 83K

• Methods Available– Hex Dominant– SweepSweep– MultiZone

• Initial RequirementsHex Dominant Meshq

– Clean geometry• Interoperability between methods

– Can be used along with other hex

Elements: 24K



methods New in AM 13.0!New in AM 13.0!


Customer Training MaterialHex Dominant Meshing• Generates unstructured hex dominant mesh• The mesh contains a combination of tet and pyramid cells with majority of

cell being of hex typef f• Useful for bodies which cannot be swept

• Useful for CFD applications not requiring inflation• Useful for CFD in the range of acceptable Skewness or Orthogonal

Q lit h lit t iQuality mesh quality metrics• Access– RMB on Mesh

Insert Method– Insert Method– Definition Method Hex Dominant



Hex Dominant Mesh


Customer Training MaterialSweep Meshing• Sweeps the surface mesh in the specified

direction– Generates hex / wedge elements

B d t h t l i ll id ti l f• Body must have topologically identical faces on two ends, (which act as source and target faces)– Topologically identical faces on two ends are

known as source and target faceso as sou ce a d ta get aces• Only one source and one target face is allowed• Thin models can have multiple source and target

faces Sweep Mesh• Access– RMB on Mesh– Insert Method

Sweep Mesh

– Definition Method Sweep




Customer Training MaterialSweep Meshing• Sweepable bodies

– ANSYS Meshing can find sweepable bodies in the geometry automatically

RMB on Mesh to find sweepable bodies

Geometry Sweepable bodies in green color




Customer Training MaterialSweep Meshing• Sweepable bodies

– Simple decomposition can give sweepable bodies– Decomposition can be performed in CAD/DM

Geometry with no sweepable body

Sweepable bodiesDecomposed Geometry

(decomposed in CAD/DM)




Customer Training MaterialSweep Meshing• Control: Source/Target Selection– Automatic

• ANSYS Meshing automatically finds source and targetM l S & M l S d T t– Manual Source & Manual Source and Target

• Required in case of defining inflation with sweep method– Automatic Thin & Manual Thin

• Multiple source and target facesMultiple source and target faces

Details View of Sweep Method



Sweep Direction Source Face Target Face


Customer Training MaterialSweep Meshing• Example:– Src/Trg Selection - Automatic

Sweepable Body Sweep Mesh No

Automatic Selection

inflation




Customer Training MaterialSweep Meshing• Example:– Src/Trg Selection – Manual

Sweepable Body Sweep Mesh

Manual Selection

pwith inflation

You cannot perform 3D inflation on bodies scoped with the Sweep methodYou can perform 2D inflation on the source face of the Sweep, provided that it has



You can perform 2D inflation on the source face of the Sweep, provided that it has been manually selected


Customer Training MaterialSweep Meshing• Example:– Src/Trg Selection - Rotational sweep for sector like geometry

Target Face

S M h W dSweepable bodies

Manual SelectionSource Face

Sweep Mesh: Wedge and Hex elements

Sweepable bodies




Customer Training MaterialSweep Meshing• Example:– Src/Trg Selection – Automatic Thin

Sweepable Body Thi S M hAutomatic ThinSweepable Body Multiple source faces

Thin Sweep MeshAutomatic Thin Selection

For multibody parts only one sweep number of divisions is allowed for Automatic or Manual Thin sweep method



allowed for Automatic or Manual Thin sweep method


Customer Training MaterialMultiZone Meshing• Based on blocking approach used in ANSYS

ICEM CFD Hexa– Automatically decomposes geometry

U t t d d t t d bl k• Uses structured and unstructured blocks• Can have multiple source and target faces• Depends on settings of Free Mesh Type

St t d bl k h d ith H– Structured blocks are meshed with Hexa orHexa/Prism

– If Free Mesh Type is set to other than NotAllowed then unstructured blocks are meshed MultiZone Meshwith Tetra, Hexa Dominant or Hex Core based onthe selected method

• Program Controlled inflation NewNew inin AMAM1313..00!!A

MultiZone Mesh

• Access– RMB on Mesh– Insert Method

Definition Method MultiZone



– Definition Method MultiZone


Customer Training MaterialMultiZone Meshing• Control:

– Src/Trg Selection - Automatic

Details View of MultiZone Method

Geometry for MultiZone Meshing

MultiZone Mesh





– Src/Trg Selection - Manual

Details View of MultiZone Method

Geometry for MultiZone Meshing

Cut section of MultiZone Mesh





– Free (unstructured) Mesh Type

Type: Tetra

Type: Hexa Dominant

Geometry



Type: Hexa Core



– Local Defeaturing Tolerance

Sliver face in the mesh

No Defeaturing

Geometry with a Small face

ignored in the mesh

C b l t ll d ith l b l

sliver face mesh

Using Defeaturing



– Can be also controlled with global defeaturing tolerance New in AM 13.0!New in AM 13.0!



CutCell Meshingg




Customer Training MaterialCutCell Meshing• Cartesian meshing method designed for

ANSYS FLUENT solver

• Patch independent volume meshing• Patch independent volume meshing approach with automatic edge defeaturing driven by advanced size functionsfunctions

• Suitable for a wide range of CFD applications

• Useful for meshing fluid bodies in single or multibody parts

• Inflation support• Access– Set Active to Yes under CutCellMeshing



New in AM 13.0!New in AM 13.0!g

option from the global control


Customer Training MaterialCutCell Meshing



Tetrahedrons Multizone Hexa dominant CutCell

Meshes from default settings. Keeping approximately the same resolution on the inlets


Customer Training MaterialCutCell Meshing main controls• Physics/Solver set to CFD/Fluent• Advanced size function– Edge proximity sources accessible and g p y

recommended for better feature capturing • Use 3D inflation• CutCellMeshing controlsg– Feature Capture (default =40)

• Smaller angle to capture more features• Angle = 0 to capture all CAD featuresAngle 0 to capture all CAD features

– Tessellation (faceting) refinement• Statistics: Orthogonal Quality suitable for

CutCell meshCutCell mesh




Customer Training MaterialCutCell Meshing Workflow• Set global CutCell meshing and sizing controls. This includes:– Set the prerequisites (CFD & Fluent preferences)– Activate the CutCell mesh method– Set CutCell meshing options (Feature Caption and Tessellation Refinement)– Set sizing options– Set global inflation controls

• Apply scoped sizings• Generate the CutCell mesh• Apply scoped inflation controls (if inflation is required)Apply scoped inflation controls (if inflation is required)• Generate the inflation mesh• Export the mesh to Fluent

Th h i t d i l h d l f t– The mesh is exported in polyhedral format

When CutCell is active some controls and features are inaccessible (see the User’s Guide for details)



are inaccessible (see the User s Guide for details)


Customer Training MaterialCutCell Meshing Workflow Example• Set global CutCell meshing controls and sizing including global inflation, if required

• Set local sizings, if required

Generate the Mesh• Set scoped inflation, if required

• Generate the inflation

g , q

Inflation is a post process for CutCell meshing. We can add/delete/modify/suppress

• Modify/delete/add inflation

local inflation settings, and the meshing process will begin with the initial mesh and inflate from there



ysettings

• Generate the inflation


Customer Training MaterialCutCell meshing limitations• Cannot be used in combination with other Meshing Methods• Only single or multi-body part meshing– Assembly meshing is available as a beta optionAssembly meshing is available as a beta option

• Feature recovery limitations– Sharp trailing edges and acute edges will produce a jagged mesh

Recovering some features might lead to bad quality– Recovering some features might lead to bad quality• Prior to meshing the user has to resolve the geometry features properly in

the CAD modeler A id t d t il– Avoid unnecessary geometry details

– Min size should be ½ of smallest 3D feature, it needs always to be adjusted • Neither Body or Surface of Influence are supported• Inflation not supported on baffles or internal walls• Ignored symmetry condition for meshingFailure in the CutCell meshing algorithm is almost always related to faceting issues in relation



to the value of Min Size. Make sure that the value of Min Size truly represents the smallest size that you want the curvature and proximity size function to capture


Customer Training MaterialCutCell meshingExample

Min size adjusted to < 0.5 the smallest targetsmallest target feature




Customer Training MaterialCutCell meshingExample

Ed i it i



Edge proximity size function source used to recover features


Customer Training MaterialCutCell meshingDLR F6 example

Engine cut Wing cut

Cp

• Meshed with default Machcutcell settings

• Converged results regardless the very small min Orthogonal Quality



• More refinement needed to get accurate results



2D & Shell Meshingg




Customer Training MaterialMeshes for 2D Analyses

• Both Fluent and the Mechanical Products in the ANSYS Portfolio accept 2D & Shell Meshes for 2D and 3D surface analyses

• For 2D analysis in FLUENT generate the mesh in XY plane (z=0). For axisymmetric applications y ≥ 0 and make sure that the domain is axisymmetric about x axis

• For 2D analysis in CFX, create a volume mesh (using Sweep) that is 1 element thick in the symmetry direction, i.e.,

– Thin Block for Planar 2D– Thin Wedge (< 5°) for 2D Axis-symmetric




Customer Training MaterialMethods for Surface Meshing• Meshing Methods for Surface Bodies

– Automatic Method (Quad Dominant)

Automatic

– Triangles– Uniform Quad/Tri– Uniform Quad

TrianglesTriangles

Uniform Quad




Customer Training MaterialSurface Meshing with Inflation• Quad mesh with Inflation

Inflation can be applied on the selected edges or named selections New in AM 13.0!New in AM 13.0!




Customer Training MaterialMapped Face Meshing: Example

Appropriate definition of vertices and edge grading results in a good structured mesh

E

E

E

E

E S

EE E

EE

SE

Vertex types are discussed in the chapter on local mesh settings in the mapped face meshing section



meshing section.


Customer Training MaterialMesh Connections• For sheet models,

connections can be defined as “Mesh Gap

connections”• Mesh connections can

be used to extend h h l lmesh at mesh level

– Tolerance Value can be specified to close gaps at mesh level

Gap removed at mesh levelConnected Mesh

gaps at mesh level• “Mesh connections”

will be created at mesh time (rather than astime (rather than as CE in solver)




Customer Training MaterialShell Meshing: Example

New in AM 13.0!New in AM 13.0!

• Edge colored by the number of connected faces

A t ti ti f h ti• Automatic generation of mesh connections

• Mesh connectivity can be shown also after meshing

• Ability to find mappable faces





New features




Customer Training MaterialDirect Meshing• With Direct Meshing from R13.0 the user has greater access

to directly mesh bodies of multibody parts• Advantages of Direct Meshing: N i AM 13 0!N i AM 13 0!• Advantages of Direct Meshing:– Bodies can be meshed individually– Mesh seeding from meshed bodies influence neighbors (user has


control)– Automated meshing can be used at any time to finish rest of meshing– When controls are added, only affected body meshes go out of date– Selective body updating– Extensive mesh method interoperability

Make sure to allow this feature under Meshing Options in ANSYS Meshing




Customer Training MaterialDirect MeshingLocal meshing• Bodies can be deleted/meshed/remeshed individually• Subsequent bodies will use the attached face mesh • The meshing results will depend on the meshing order• RMB on the body(ies) and generate the mesh locally

Automated Meshing first Meshing first meshing

gthe block

then the pipe

gthe pipe then

the block

Hexas Hexas Wedges

Meshed with default meshing settings




Customer Training MaterialDirect MeshingLocal remeshing• Once a multibody part is meshed we can decide

later on to put more controls on a set of bodies, hsuch us:

– Local sizings, inflation, BOI, etc• Put the controls, RMB on the select the body(ies),

clean the mesh and remesh locallyclean the mesh. and remesh locally

Geometry with a BOI inside

With BOIBOI

Without BOIBOI

Only the affected body is remeshed. The mesh on the



adjacent bodies remains unchanged


Customer Training MaterialDirect MeshingSelective body updating

• Only modified body(ies) is remeshed. The mesh on the adjacent bodies remains unchangedg

• Significant time savings on model change

• The user can have more control by allowing Smartcontrol by allowing Smart CAD Update and Compare Parts On Update, see User’s Guide for details




Customer Training MaterialMesh Method Interoperability• Now there is method interoperability

between all mesh methodsPatch Independent

tetrahedrons (Smooth Transition On)


Hexa Dominant


Multizone

Sweep Patch Independent



Patch Conforming tetrahedrons

Sweep Patch Independent tetrahedrons

(Smooth Transition Off)


Customer Training MaterialParameterization in ANSYS MeshingMeshing controls can now be parameterized– Global controls and local controls– Selection of parameter promotes the parameter to the WB project page– Geometry and Meshing parameters can be related using expressions in the

parameter manager

New in AM 13 0!New in AM 13 0!New in AM 13.0!New in AM 13.0!




Customer Training MaterialParameterization project example

• Number of divisions on the outlet pipe equal to two times its length• Number of divisonson the inlet pipe equalon the inlet pipe equal to its length + 4

2 di

visi

ons

Outlet



8+4=

12

Inlet


Customer Training MaterialParameterization project example (Con’t)





APPENDIXAPPENDIX




Customer Training MaterialSweep Meshing




Customer Training MaterialSurface Meshing with Inflation• Triangular Mesh with ‘Inflation’




Customer Training MaterialCutCell meshingBlower example Inlet_duct part Casting part

Assembly of parts meshed y pwith the beta option using

default cutcell settings

All beta features are accessible by allowing Beta Options under Tools/Options/Appearance in ANSYS Workbench



Tools/Options/Appearance in ANSYS Workbench


Customer Training MaterialExtended Meshing• Add-on to ANSYS Meshing to provide Extending Meshing• ANSYS Extended Meshing enables:

– Running ICEM CFD or TGrid stand-alone– Running ICEM CFD or TGrid from the ANSYS Meshing application

using:using:• Interactive/Batch scripting options for “Write ICEM CFD Files”• Interactive TGrid as part of CutCell meshing (beta)



AM-Intro 13.0 L02 Meshing Methods

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