ANSYS 14 Meshing Automatic Robust Meshing

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Transcript of ANSYS 14 Meshing Automatic Robust Meshing

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    2011 ANSYS, Inc. November 22,

    2011

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    Automatic & Robust

    Meshing in Fluids

    2011 ANSYS Regional Conferences

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    Assembly Meshing enables dramatically

    reduced time to mesh for typical CADmodels by eliminating the tediousgeometry clean-up

    Top-down approach to mesh all parts atonce

    Uses Virtual Bodies (material points) toautomatically extract internal regionsfrom assemblies

    Supports:

    Meshing solids from sheet bodiesforming a closed domain

    Conformal mesh between partswithout requiring multibody parts

    Overlapping bodies

    Tet (linear) and CutCell (hex-dominant)mesh types

    Program Controled Inflation

    Automatic & Robust Meshing Assembly Meshing

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    1. The Customer Problem

    2. Assembly meshing overview

    3. New Features

    1. Flow Volume Extraction

    2. Sharp Angle, Thin Sections

    3. Contacts and Leak closing

    4. Demo: Mixing Tank

    5. Miscellaneous features

    6. Summary

    Agenda

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    Automatic & Robust

    Meshing in Fluids

    The Customer Problem

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    CFD users need a quick way to generate the fluid volume mesh from complex

    assemblies of geometric solid parts.

    Geometry tolerances often require more accurate resolution of data (and more

    work to achieve it) that the mesh later ignores as the mesh size is relatively much

    larger.

    The parts may not be in contact with each other, and they may contain sharp

    angles, thin sections and gaps.

    Poor CAD models that dont form watertight solid geometry.

    By combining the flow volume extraction and meshing operations, the overall

    meshing time and efficiency of the meshing workflow can be improved.

    Solution: Assembly meshing

    Assembly Meshing Motivation

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    The overall meshing process can often get elongated if the geometry is complex:

    Assembly Meshing in Fluids:Process Compression

    Mesh GenerationMesh SetupGeometry Prep

    Mod

    elComplexity

    Time to Mesh

    MeshGeneration

    MeshSetup

    GeometryPrep

    Low Complexity

    Mesh

    Generation

    Mesh

    Setup

    Geometry

    Prep

    Med Complexity

    MeshGeneration

    MeshSetup

    GeometryPrep

    High Complexity

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    Assembly Meshing:Process Compression

    Mod

    elComplexity

    Time to Mesh

    Assembly meshing reduces the overall meshing time, bycombining the flow volume extraction and meshing

    operations.

    MeshGeneration

    MeshSetup

    Assembly Meshing:

    GeometryPrep

    Note: Mesh Generation timeis slightly longer, but overall

    time is significantly reduced.

    Part Meshing:

    MeshGeneration

    MeshSetup

    GeometryPrep

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    Flow volume extraction: Three simple steps

    1. Define Coordinate system inside the Fluid Void

    2. Insert a Virtual body

    3. Assign the proper CoordinateSystem to the Material Point

    4. Done

    R14 Assembly Meshing:Flow Volume Extraction

    #1

    #2

    #3

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    R14 Assembly Meshing:Keep Solid Mesh

    In the Assembly Meshing panel, you can choose tokeep or discard the mesh in all solids

    Parts can be marked

    as Fluids/Solids

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    R14 Inflation Improvements

    Industrial Example: 68 Million cells, 5 inflation layers

    Total Mesh Time:

    R13: 6 hrs 39 mins

    R14: 3 hrs 38 mins

    Speed and Flexibility of inflation: Several improvements to both

    assembly and part meshing

    Better quality during stair stepping

    Better handling of high aspect ratio inflation

    Improved Speed of inflation creation ~30-100%

    Assembly Meshing Flexibility

    Cutcell: Full support of 2-stage inflation CutCell and inflation in two separate steps

    Tetrahedron: Uses pre-inflation

    Faster, more layers, and better quality

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    Also supported for Virtual Bodies

    Program controlled inflation acts only on Fluid Bodies

    R14 Assembly Meshing:Automatic Inflation

    CutCell + Inflation Tetrahedron + Inflation

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    Sharp angle tool

    A special cell cutting algorithm has been developed toproperly capture sharp 3D angles

    Can be used to improve feature capturing in general

    Insert a Sharp Angle and pick adjacent faces

    Example:

    R14 Assembly Meshing:

    Sharp angles in the Flow volume of drill bit

    Mesh without Sharp Angle

    Mesh with Sharp Angle

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    R14 Assembly Meshing Leak Handling

    CFD users often need to extract the flow volume from CAD using Fill,Stitch or Boolean operations.

    Because of missing rubber seals, bad CAD, imposed tolerances, etc.,

    gaps appear in the model and creation of the flow volume might fail.

    Finding and closing these gaps in CAD can be tedious.

    Solution:

    Assembly meshing solves this problem in several ways:1. Tolerances only need to be resolved to level of discretization of mesh

    2. Gaps that are still too large can be visualized through leakageidentification

    3. Tools to guide mesher in resolving gaps

    Image Courtesy of Delphi Harrison Thermal Systems

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    Find leaks using material points: Any time you are using material points (for internal flow), and it is

    leaking to the outside, you can automatically see the

    leak-path together with the surface mesh

    R14 Assembly Meshing Leak Handling:Leakage Path

    There is a small gap between the valve plug and the valve seat

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    Using Contacts for Assembly meshing:

    Workbench has extensive capabilities to detect contact

    (interfaces) between parts.

    Until now, that contact information has been of little use to

    FLUENT users, but that is changing at R14. Contacts have several purposes for

    Assembly Meshing:

    Closing of small gaps using contact sizing

    Find thin sections

    Find Contacts

    Features at contact pairs are preserved

    Contacts are also used in Fluid Surface

    picker helper

    R14 Assembly Meshing Leak Handling:Contact (Interface) Regions

    For example, in this image

    the circled edges would be

    removed without contact

    defined since the feature

    angle is below the default

    (40 degrees)

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    Closing a leak: Three simple steps

    1. Define a Contact betweenthe entities that are leaking

    Edge/face or Face/Face

    2. Drag and drop the contacton top of the Mesh Icon

    Creates a Contact sizing

    3. Adjust Contact sizing Use roughly 1/5 of min-size

    4. Assembly Meshing

    R14 Assembly Meshing Leak Handling:Closing Leaks

    #1

    #2

    #3

    Pick the face of the valve plug (blue)

    and the edge of the valve seat (red)

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    Why locate thin sections (3D bodies)?

    The assembly meshing method produces better quality

    meshes if thin baffles and fins are well resolved

    By using the Find Thin Sections tool, these can be foundin advance and appropriate sizing can be applied

    R14 Assembly Meshing:Finding Thin Sections

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    Automatic & Robust

    Meshing in Fluids

    Assembly meshing: Mixing Tank Demo

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    R14 Assembly Meshing - Demo

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