meshing techniques in ansys icem cfd 5.0

ANSYS, Inc. Proprietary© 2004 ANSYS, Inc.

Meshing Techniques in Ansys ICEM CFD 5.0

Meshing Techniques in Ansys ICEM CFD 5.0

Christian NienhüserANSYS Germany

Christian.Nienhueser@ansys.com

October 2004 CADFEM CZ User’s Meeting Slide 2

Contents

• New Graphic User Interface• Geometry import, clean up• Meshing Tools

– Surface meshing• Patch based • Patch independent

– Volume meshing• Tetrahedral• Hexahedral• Hybrid

• Outlook• Final remarks

October 2004 CADFEM CZ User’s Meeting Slide 3

Export to AnalysisOver 100 supported solver formats.

What is ANSYS ICEM CFD?

Direct CADCATIA, Pro/E, I-DEAS,

UG, SE, SW…

3rd Party CADIGES, ACIS, Parasolid…

Faceted Data

STL, Nastran, Patran, VRML…

ICEM CFDComplete CAE Pre-processing

• Create/Edit geometry • Generate mesh• Edit Mesh• Apply Poperties, B.C.’s

October 2004 CADFEM CZ User’s Meeting Slide 4

Classic GUI

ICEM CFD 4.2

Development Process

ICEM CFD 4.CFX AI*Environment 1.0

AI*Environment / ICEM CFD 5.0

AI*Environment 2.0ICEM CFD 4.3

Classic GUI ICEM CFD / AI*Environment 5.1

October 2004 CADFEM CZ User’s Meeting Slide 5

New Graphic User Interface

• User interface completely redesigned

• Integrates Med, Tetra, Prism, Hexa and Visual3

• Layout is– Clean– Modern– Intuitive

October 2004 CADFEM CZ User’s Meeting Slide 6

New Graphic User Interface

• Tabbed menus which follow the process

• Logical function groups

• Model tree– For display

control– Right-click

to access related options and operations

October 2004 CADFEM CZ User’s Meeting Slide 7

New Graphic User Interface

Selection and database management• Selection manager• Selection filters• Part selection by entity

• Blanking of specific entities• Improved subsets for geometry/mesh

– Easier methods of limiting data displayed

October 2004 CADFEM CZ User’s Meeting Slide 8

New Graphic User Interface

• Advanced help browser

• Quick-help

October 2004 CADFEM CZ User’s Meeting Slide 9

Geometry Import

Direct CADCATIA, Pro/E, I-DEAS,

UG, SolidWorks …

Direct CADCATIA, Pro/E, I-DEAS,

UG, SolidWorks …

CATIA

Unigraphics

Generic CADIGES, ACIS, DWG, STEP …

Generic CADIGES, ACIS, DWG, STEP …

SolidWorksSolidWorks

Faceted Data

STL, NASTRAN, Patran, VRML…

Faceted Data

STL, NASTRAN, Patran, VRML…

STL

ANSYS ICEM CFD

October 2004 CADFEM CZ User’s Meeting Slide 10

Geometry Import

Hexa for CATIA V5

October 2004 CADFEM CZ User’s Meeting Slide 11

Model Diagnosis and Repair

Build topology function• Tolerance is set automatically on import• Curves are extracted from surface model• Enables model diagnosis• Curves form basis for geometry repair

Imported CADImported CAD

October 2004 CADFEM CZ User’s Meeting Slide 12

Geometry tools

Repair•Topology checker to find problems in surface data•Surface closing•Surface retrimming/matching •Surface extension•Unsplit surface•Split by curvature•Modify surface normals•Bolt hole detection•Button detection•Fillet detection

Surface editing•Surface from curves•Driven surface•Swept surface•Revolved surface•Offset surface•Midsurface•Adjust thickness•Lofted surface

Body definitions•From connectivity•Point inside solid

Point creation•From screen•Explicit•Offset•Centerpoint•Between points•Endpoint•Intersection•Along curve•Projection to curve/surface

Curve creation•From points•Arc/Circle•Surface param•Intersection•Surface projection•Concatenation•Segmentation•Surface Boundary•Faceted curve tools

•Curtain surface•Surface trimming

•Merged surface

•Shrink wrapped surface

•Standard surfaces

•Faceted Surface tools

October 2004 CADFEM CZ User’s Meeting Slide 13

STL to B-Spline conversion

• Use geometry repair• Convert multiblock

mesh to b-spline• Reverse engineering

and legacy data support

Circle fom points

October 2004 CADFEM CZ User’s Meeting Slide 14

Quad surface meshing

• All-quadrilateral mesh

• Edge model

• CAD geometry

patch dependent

October 2004 CADFEM CZ User’s Meeting Slide 15

Quad Surface Meshing

• Mapping = 0 • Mapping = 0.2

Auto-structured meshing

October 2004 CADFEM CZ User’s Meeting Slide 16

Extensions

• Arbitrary boundary• Holes, prescribed

curves and prescribed points

• One/some transition triangles

• Auto-structured• Mesh refinement

October 2004 CADFEM CZ User’s Meeting Slide 17

Surface meshing enhancements

• Unstructured quad meshing algorithm integrated into Hexa mesher.

– Allows the easy creation of hybrid structured/unstructured meshes.

– Ideal mesh for crash and NVH.

• Initial auto blocking from CAD surfaces.

– Automatic merging of regions to create a better blocking.

– Geometry feature recognition in meshing.

October 2004 CADFEM CZ User’s Meeting Slide 18

Tetra meshing (Octree)

• Initial mesh of “Maximum size” elements fills a bounding box

October 2004 CADFEM CZ User’s Meeting Slide 19

Tetra meshing (Octree)

• Mesh is subdivided to meet specified sizes

• Nodes adjusted to conform to geometry

October 2004 CADFEM CZ User’s Meeting Slide 20

Tetra meshing (Octree)

• “Flood fill” process finds volume boundaries

October 2004 CADFEM CZ User’s Meeting Slide 21

Tetra meshing (Octree) Patch Independence

– Mesh “walks over” gaps, overlaps, holes, details– A perfect CAD model is not required– Greatly reduces the amount of required CAD cleanup

Surfaces near stamped label

Mesh “walks over” the detail

October 2004 CADFEM CZ User’s Meeting Slide 22

Tetra meshing (Octree)

• Improved: ‘bounding box’ by ‘geometry blow-up’

October 2004 CADFEM CZ User’s Meeting Slide 23

Tetra meshing: Improved Auto-Volume Detection

• Material points are automatically created – Multiple volumes are supported

October 2004 CADFEM CZ User’s Meeting Slide 24

Tetra meshing: Part-by-Part

• Enables assemblies to be meshed in batch as component parts

• Mesh is non-conformal

October 2004 CADFEM CZ User’s Meeting Slide 25

Tetra meshing: Improved Volume Mesh Controls

• Point, line, and volume density– Width parameter extends effect

• Volume defined by points or by bounding box around selected entities

Point density

October 2004 CADFEM CZ User’s Meeting Slide 26

Hybrid meshes

• Tet to hex converter

October 2004 CADFEM CZ User’s Meeting Slide 27

Prism meshing

• Prism layers in pure tetra meshes

October 2004 CADFEM CZ User’s Meeting Slide 28

Prism meshing

• Prism layers in hybrid meshes– Extrusion of

mixed quad/triangle meshes.

October 2004 CADFEM CZ User’s Meeting Slide 29

Hybrid meshing

• New hexahedral-dominant meshing

October 2004 CADFEM CZ User’s Meeting Slide 30

Hybrid meshing (outside of Hexa)

• Volume tetra -> add prisms -> convert interior to hexas.

• Surface tri/quad mesh -> add prisms -> fill with tets.

• Surface quad mesh -> add boundary hexas -> fill with hexas/tetras/pyramids/prisms

Easily in any order/any element type

October 2004 CADFEM CZ User’s Meeting Slide 31

Hexa meshing

Geometry Blocking Mesh

• Multi-block structured

October 2004 CADFEM CZ User’s Meeting Slide 32

Auto 2-D blocking approach

Free block

Mapped block

• Each Rectangular surface gets a mapped block.

• Arbitrary surfaces get free blocks.• Blocks are independent of surface

topology (morphable).• Geometry recognition is used to group

potentially problem surfaces.

October 2004 CADFEM CZ User’s Meeting Slide 33

Hex or hex dominant meshes

• Multiple automatic pathways to high quality all hex or hex dominant meshes.– Auto surface blocking followed by auto

volume blocking.

– Direct block decomposition method.

– Auto surface blocking into surface meshing into hex dominant volume meshing.

– Hexa tools can be used to assist either the surface blocking or the volume blocking.

• Better parametric association• Hybrid meshing framework

October 2004 CADFEM CZ User’s Meeting Slide 34

Auto blocking from surface blocking

• Start from CAD surfaces.

• Generate Auto 2-D blocks based on surfaces

• Generate Auto 3-D blocks by filling in 2-D blocks with Hex dominant mesher

• Automatically create mesh spacing and mesh with existing Hexa techniques.

• Results in a high-quality all hex mesh.

All Hex

October 2004 CADFEM CZ User’s Meeting Slide 35

True automatic blocking

Produces great blocking but sensitive to geometric details

October 2004 CADFEM CZ User’s Meeting Slide 36

Hex meshing: Hex dominant mesher

• Start from CAD geomety• Generate all quad surface mesh as

before• Automatically fills surface mesh with

uniform hex dominant mesh• User can then edit the hex dominant

mesh by automatic smoothing and mesh editing

HEXA_8 : 4849

PENTA_6 : 287

PYRA_5 : 640

TETRA_4 : 313

October 2004 CADFEM CZ User’s Meeting Slide 37

HEXA: System level

Hexa will do the bookkeeping to keep track of the connectivity of hybrid meshes.

• Structured blocks.• Extruded blocks

– All Quad– Quad + 1 Tri– Quad dominant– All Tri

• Unstructured blocks:– Filled by Tetra– Filled by Hex-Dominant mesher– Filled by Delaunay mesher.

October 2004 CADFEM CZ User’s Meeting Slide 38

Final remarks

• Thank you!

• Questions?