ANSYS Meshing Advanced Techniques

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17.0 Release

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ANSYS Meshing Overview

Advanced Tet Methods

Advanced Hex Methods

Selective Meshing Methods

Using Global Meshing Methods

Using Local Meshing Methods

Clean Up Tools

Quality Metrics

Meshing Tips and Tricks

Overview

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ANSYS Meshing is a component of ANSYS Workbench Meshing platform

Combines and builds on strengths of preprocessing offerings from ANSYS: ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh, Gambit

Able to adapt and create Meshes for different Physics and Solvers CFD: Fluent, CFX and POLYFLOW

Mechanical: Explicit dynamics, Implicit

Electromagnetic

Integrates directly with other WB systems

What is ANSYS Meshing

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What are the Element Types Tetrahedral

Hexahedral

Polyhedral (CFD)

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Advanced Tet Methods

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Choosing the proper mesh element type will improve the mesh generation efficiency

Small mesh size on holes need to transition to larger size elsewhere, but transitioning hex mesh can be a problem

Tet mesh can be easily converted to hex mesh, but if the quality is bad,

whats the point?

1 tet to 4 hex

All Hex

Hexahedral vs. Tetrahedral Elements

Advantages of tetrahedral over hexahedral:

Easier to mesh more complex geometry: Mesh quality is often easier to achieve with tetrahedral (or poly)

mesh

Mesh transitioning with hex mesh can be problematic

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Patch Conforming versus Independent

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Bottom up approach: Meshing process Edges Faces volume

All faces and their boundaries are respected(conformed to) and meshed (except with defeaturing tolerance)

Good for high quality (clean) CAD geometries CAD cleanup required for dirty geometry

Sizing is defined by global and/or local controls Compatible with inflation

To access it Insert Method

Set to Tetrahedrons Set to Patch Conforming

Patch Conforming

Top down approach: Meshing process Volume meshed first projected on to faces

& edges Faces, edges & vertices not necessarily conformed

Controlled by tolerance and scoping of Named Selection, load or other object

Good for gross de-featuring of poor quality (dirty) CAD geometries

Method Details contain sizing controls Compatible with inflation

To access it Insert Method

Set to Tetrahedrons Set to Patch Independent

Patch Independent

Tetrahedral Methods

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Geometry with small details

Patch conforming : details caputredPatch independent : details ignored

Delaunay mesh - smooth growth rate Octree mesh . approximate growth rate

Tetrahedral Method: Algorithm comparison

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Advanced Hex Methods

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Advantages of hexahedral over tetrahedral:

Less elements = Faster solution time with better accuracy

Naturally anisotropic: Fewer elements required as mesh is aligned with the physics

Fewer elements for given number of nodes

3 mostly parallel sets of faces (improves solution accuracy)

However, this assumes the geometry is such that the hex mesh is more efficient and that the structured mesh aligns to the physics

Hexahedral versus Tetrahedral Elements

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Hex Meshing Reduced element count

Reduced run time

Elements aligned in direction of flow

Reduced numerical error

Initial Requirements Clean geometry

May require geometric decomposition

Tetra mesh - 48 000 Cells

Hexa mesh - 19 000 Cells

Hexahedral Mesh

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Automatic Source & Target faces identified automatically

Requires that the mesher find the sweeping direction

Manual source & Manual source and target User selection Source face colored in red Target face colored in blue Rotational Sweeping

Sweep around an axis Requires selection of both - Source & target

Note Specifying both Source & Target accelerate

meshing

Source & Target selection

Define the numberof intervals on the

side face(s)

Sweep Path

Generation of wedges& hex elements

Sweep Meshing

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Based on blocking approach (ANSYS ICEM CFD Hexa)

Automatically decomposes geometry into blocks Generates structured hexa mesh where block

topology permits Remaining region filled with unstructured

Hexa Core or Tetra or Hexa dominant mesh Src/Trg Selection

Automatic or Manual source selection Multiple source faces Select Target faces as Source

Compatible with 3D Inflation

To access it Insert Method Set to Multizone

Mesh Method & Behavior

Multizone Meshing

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Combination of Tetrahedron Patch Conforming and Sweep Method

Automatically identifies sweepable bodies and creates sweep mesh

All non-sweepable bodies meshed using tetrahedron Patch Conformal method

Compatible with inflation

To access it Default method Insert method Set to Automatic

Mesh Method & Behavior

Automatic Method

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Meshing Options

Global Meshing Parameters

Local Meshing Parameters

Global Settings - Physics Preference- Shape Checking

Global Sizing- Size Functions- Relevance Center

Mesh Method- Tet, Hex,

Multizone, Sweep

Mesh Statistics

Advanced Settings- Number of CPUS

Global Inflation Layers Local Sizings- Edge, Face, Body

Mesh Edit Tools- Node move/merge- Contact Match

Advanced Tools- Inflation, Pinch and match controls

Global Meshing Parameters

Local Meshing Parameters

Global Settings - Physics Preference- Shape Checking

Global Sizing- Size Functions- Relevance Center

Mesh Method- Tet, Hex,

Multizone, Sweep

Advanced Settings- Number of CPUS

Global Inflation Layers Local Sizings- Edge, Face, Body

Advanced Tools- Inflation, Pinch and match controls

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Global Meshing Methods

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Global mesh controls are used to make global adjustment in the meshing strategy, which includes sizing functions, inflation, smoothing, defeaturing, parameter inputs, assembly meshing

Minimal inputs Automatically calculates global element sizes

based on the smallest geometric entity

Smart defaults are chosen based on physics preference

Makes global adjustments for required level of mesh refinement

Advanced Size Functions for resolving regions with curvatures and proximity of surfaces Smart defaults !

Global Mesh Controls

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Five options under Physics Preference Mechanical, Nonlinear Mechanical, Electromagnetics, CFD and Explicit

Three options under Solver Preference when CFD is selected Fluent, CFX and Polyflow

Mesh setting defaults are automatically adjusted to suit the Physics Preference and Solver Preference

Defaults

The Nonlinear Mechanical Physics Preference Option has been added in R17.0 and may results in higher mesh quality for FEA users

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Controls the growth and distribution of mesh in important regions of high curvature or close proximity of surfaces

Five Options: Adaptive

Proximity and Curvature

Curvature

Proximity

Uniform

When CutCell Meshing is active with Proximity or Proximity and Curvature, Proximity Size Function Sources control is displayed to specify the regions of proximity between Edges, Faces or Faces and Edges in the computation of Proximity Size Function (SF)

Sizing: Size Function

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SF: Curvature

Determines the Edge and Face sizes based on Curvature Normal Angle

Finer Curvature Normal Angle creates finer surface mesh

Transition of cell size is defined by Growth Rate

SF: Adaptive

The edges a