Transcript Document

Meshing Techniques in
Ansys ICEM CFD 5.0
Christian Nienhüser
ANSYS Germany
[email protected]
© 2004 ANSYS, Inc.
ANSYS, Inc. Proprietary
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 2
What is ANSYS ICEM CFD?
Direct CAD
3rd Party CAD
Faceted Data
CATIA, Pro/E, I-DEAS,
UG, SE, SW…
IGES, ACIS, Parasolid…
STL, Nastran,
Patran, VRML…
ICEM CFD
Complete CAE
Pre-processing
• Create/Edit geometry
• Generate mesh
• Edit Mesh
• Apply Poperties, B.C.’s
Export to Analysis
Over 100 supported solver formats.
October 2004
CADFEM CZ User’s Meeting
Slide 3
Development Process
ICEM CFD 4.2
ICEM CFD 4.CFX
ICEM CFD 4.3
AI*Environment 1.0
AI*Environment 2.0
Classic GUI AI*Environment / ICEM CFD 5.0
Classic GUI ICEM CFD / AI*Environment 5.1
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CADFEM CZ User’s Meeting
Slide 4
New Graphic User Interface
• User interface
completely
redesigned
• Integrates Med,
Tetra, Prism,
Hexa and
Visual3
• Layout is
– Clean
– Modern
– Intuitive
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CADFEM CZ User’s Meeting
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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
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CADFEM CZ User’s Meeting
Slide 6
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
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CADFEM CZ User’s Meeting
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New Graphic User Interface
• Advanced help
browser
• Quick-help
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Slide 8
Geometry Import
Unigraphics
CATIA
STL
Direct CAD
CATIA, Pro/E, I-DEAS,
UG, SolidWorks …
Generic CAD
IGES, ACIS, DWG, STEP …
Faceted Data
STL, NASTRAN,
Patran, VRML…
ANSYS ICEM CFD
SolidWorks
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CADFEM CZ User’s Meeting
Slide 9
Geometry Import
Hexa for CATIA V5
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Slide 10
Model Diagnosis and Repair
Build topology function
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Tolerance is set automatically on import
Curves are extracted from surface model
Enables model diagnosis
Curves form basis for geometry repair
Imported CAD
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Slide 11
Geometry tools
Body definitions
Repair
•Topology checker
to find problems
in surface data
Surface editing
•Surface closing
•Surface from curves •Curtain surface
•Surface
•Driven surface
•Surface trimming
retrimming/matching
•Swept surface
•Surface extension
•Merged surface
•Revolved surface
•Unsplit surface
•Shrink wrapped
•Offset surface
•Split by curvature
surface
•Midsurface
•Modify surface
•Standard surfaces
normals
•Adjust thickness
•Faceted Surface tools •Bolt hole detection
•Lofted surface
•Button detection
•Fillet detection
•From connectivity
•Point inside solid
Point creation
•From screen
•Explicit
•Offset
•Centerpoint
•Between points
•Endpoint
•Intersection
•Along curve
•Projection to
curve/surface
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Curve creation
•From points
•Arc/Circle
•Surface param
•Intersection
•Surface projection
•Concatenation
•Segmentation
•Surface Boundary
•Faceted curve tools
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STL to B-Spline conversion
Circle fom points
• Use geometry repair
• Convert multiblock
mesh to b-spline
• Reverse engineering
and legacy data
support
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Slide 13
Quad surface meshing
patch dependent
• CAD geometry
• All-quadrilateral mesh
• Edge
model
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Quad Surface Meshing
Auto-structured meshing
• Mapping = 0
October 2004
• Mapping = 0.2
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Extensions
• Arbitrary boundary
• Holes, prescribed
curves and
prescribed points
• One/some transition
triangles
• Auto-structured
• Mesh refinement
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CADFEM CZ User’s Meeting
Slide 16
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.
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Slide 17
Tetra meshing (Octree)
• Initial mesh of “Maximum
size” elements fills a
bounding box
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Slide 18
Tetra meshing (Octree)
• Mesh is subdivided
to meet specified
sizes
• Nodes adjusted to
conform to
geometry
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Slide 19
Tetra meshing (Octree)
• “Flood fill” process
finds volume
boundaries
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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
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Mesh “walks over”
the detail
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Tetra meshing (Octree)
• Improved: ‘bounding box’
by ‘geometry blow-up’
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Tetra meshing: Improved AutoVolume Detection
• Material points are automatically created
– Multiple volumes are supported
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Slide 23
Tetra meshing: Part-by-Part
• Enables assemblies to be meshed in batch as
component parts
• Mesh is non-conformal
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Slide 24
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 Point density
entities
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Slide 25
Hybrid meshes
• Tet to hex converter
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Slide 26
Prism meshing
• Prism layers in pure tetra meshes
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Slide 27
Prism meshing
• Prism layers in
hybrid meshes
– Extrusion of
mixed
quad/triangle
meshes.
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CADFEM CZ User’s Meeting
Slide 28
Hybrid meshing
• New hexahedral-dominant meshing
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Slide 29
Hybrid meshing (outside of Hexa)
Easily in any order/any element type
• 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
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Slide 30
Hexa meshing
• Multi-block structured
Geometry
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Blocking
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Mesh
Slide 31
Auto 2-D blocking approach
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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.
Mapped block
Free block
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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
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Slide 33
Auto blocking from surface blocking
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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
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True automatic blocking
Produces great blocking but sensitive to geometric details
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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
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Slide 36
HEXA: System level
Hexa will do the bookkeeping
to keep track of the
connectivity of hybrid meshes.
• Structured blocks.
• Extruded blocks
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All Quad
Quad + 1 Tri
Quad dominant
All Tri
• Unstructured blocks:
– Filled by Tetra
– Filled by Hex-Dominant mesher
– Filled by Delaunay mesher.
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CADFEM CZ User’s Meeting
Slide 37
Final remarks
• Thank you!
• Questions?
October 2004
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Slide 38