Ansys ICEM CFD 10.0 Manual

1287 Pages·2006·17.44 MB·English

ANSYS ICEM
CFD/AI*Environment
10.0 User Manual

ANSYS ICEM CFD/AI*Environment
10.0 User Manual

Table of Contents
1. CAD Repair .......................................................................................................................................... 1–1
1.1. How are Close Holes and Remove Holes different? ......................................................................... 1–1
1.1.1. Close Holes .......................................................................................................................... 1–1
1.1.2. Remove Holes ...................................................................................................................... 1–2
1.2. How do Fill, Trim and Blend work in Stitch/Match Edges? ............................................................... 1–3
1.3. How does Match work in Stitch/Match Edges? ............................................................................... 1–5
2. Tetra .................................................................................................................................................... 2–1
2.1. Introduction ................................................................................................................................. 2–1
2.1.1. Tetra mesh generation ......................................................................................................... 2–1
2.1.2. Input to Tetra ....................................................................................................................... 2–1
2.2. Tetra Generation Steps ................................................................................................................. 2–2
2.2.1. Repair Geometry .................................................................................................................. 2–2
2.2.2. Geometry Details Required ................................................................................................... 2–3
2.2.3. Sizes on surfaces and curves ................................................................................................. 2–4
2.2.4. Meshing inside small angles or in small gaps between objects .............................................. 2–5
2.2.5. Desired Mesh Region ........................................................................................................... 2–5
2.2.6. Run Tetra - The Octree Approach .......................................................................................... 2–5
2.3. Important Features in Tetra ......................................................................................................... 2–12
2.3.1. Natural Size ........................................................................................................................ 2–12
2.3.2. Tetrahedral Mesh Smoother ............................................................................................... 2–12
2.3.3. Tetrahedral Mesh Coarsener ............................................................................................... 2–13
2.3.4. Triangular Surface Mesh Smoother ..................................................................................... 2–13
2.3.5. Triangular Surface Mesh Coarsener ..................................................................................... 2–13
2.3.6. Triangular Surface Editing Tools ......................................................................................... 2–13
2.3.7. Check Mesh ....................................................................................................................... 2–13
2.3.8. Quality metric .................................................................................................................... 2–18
2.3.9. Advanced options .............................................................................................................. 2–18
3. Hexa .................................................................................................................................................... 3–1
3.1. Introduction ................................................................................................................................. 3–1
3.2. Features of Hexa ........................................................................................................................... 3–1
3.3. Mesh Generation with Hexa .......................................................................................................... 3–2
3.4. The Hexa Database ....................................................................................................................... 3–2
3.5. Intelligent Geometry in Hexa ........................................................................................................ 3–2
3.6. Unstructured and Multi-block Structured Meshes .......................................................................... 3–3
3.6.1. Unstructured Mesh Output: .................................................................................................. 3–3
3.6.2. Multi-Block Structured Mesh Output: .................................................................................... 3–3
3.7. Blocking Strategy .......................................................................................................................... 3–3
3.7.1. Split ..................................................................................................................................... 3–4
3.7.2. Merge .................................................................................................................................. 3–4
3.8. Using the Automatic O-grid .......................................................................................................... 3–4
3.9. Most Important Features of Hexa .................................................................................................. 3–6
3.10. Automatic O-grid generation ...................................................................................................... 3–6
3.10.1. Important Features of an O-grid ......................................................................................... 3–7
3.11. Edge Meshing Parameters .......................................................................................................... 3–7
3.12. Smoothing Techniques ............................................................................................................... 3–7
3.13. Refinement and Coarsening ........................................................................................................ 3–8
3.13.1. Refinement ........................................................................................................................ 3–8
3.13.2. Coarsening ........................................................................................................................ 3–8
3.14. Replay Functionality ................................................................................................................... 3–8
3.14.1. Generating a Replay File ..................................................................................................... 3–8
ANSYS ICEM CFD/AI*Environment 10.0 User Manual . . ' SAS IP, Inc.
ANSYS ICEM CFD/AI*Environment 10.0 User Manual
3.14.2. Advantage of the Replay Function ..................................................................................... 3–8
3.15. Periodicity .................................................................................................................................. 3–8
3.15.1. Applying the Periodic Relationship .................................................................................... 3–9
3.16. Mesh Quality .............................................................................................................................. 3–9
3.16.1. Determining the Location of Cells ....................................................................................... 3–9
3.16.2. Determinant ...................................................................................................................... 3–9
3.16.3. Angle ................................................................................................................................. 3–9
3.16.4. Volume .............................................................................................................................. 3–9
3.16.5. Warpage ............................................................................................................................ 3–9
4. Properties ............................................................................................................................................ 4–1
4.1. Create Material Property ............................................................................................................... 4–1
4.2. Save Material ................................................................................................................................ 4–1
4.3. Open Material ............................................................................................................................... 4–1
4.4. Define Table ................................................................................................................................. 4–1
4.5. Define Point Element .................................................................................................................... 4–1
4.6. Define Line Element ...................................................................................................................... 4–1
4.7. Define Shell Element .................................................................................................................... 4–1
4.8. Define Volume Element ................................................................................................................ 4–1
5. Constraints ......................................................................................................................................... 5–1
5.1. Displacement on Point .................................................................................................................. 5–1
5.2. Displacement on Curve ................................................................................................................. 5–1
5.3. Displacement on Area ................................................................................................................... 5–1
5.4. Displacement on Subset ............................................................................................................... 5–1
5.5. Define Contact ............................................................................................................................. 5–1
5.5.1. Automatic Detection ............................................................................................................ 5–1
5.5.2. Manual Definition ................................................................................................................ 5–1
5.6. Define Single Surface Contact ...................................................................................................... 5–1
5.7. Define Initial velocity .................................................................................................................... 5–1
5.8. Define Planar Rigid wall ................................................................................................................ 5–1
6. Loads ................................................................................................................................................... 6–1
6.1. Force on Point .............................................................................................................................. 6–6
6.2. Force on curve .............................................................................................................................. 6–6
6.3. Force on Surface ........................................................................................................................... 6–7
6.4. Force on Subset ............................................................................................................................ 6–7
6.5. Pressure on surfaces ..................................................................................................................... 6–7
6.6. Pressure on subset ........................................................................................................................ 6–7
6.7. Temperature on Points ................................................................................................................. 6–7
6.8. Temperature on curves ................................................................................................................. 6–7
6.9. Temperature on Surface ............................................................................................................... 6–7
6.10. Temperature on Body ................................................................................................................. 6–7
6.11. Temperature on Subset ............................................................................................................... 6–7
6.12. Set Gravity .................................................................................................................................. 6–7
7. Solver Options ..................................................................................................................................... 7–1
7.1. Setup Solver Parameters. .............................................................................................................. 7–1
7.2. Setup Analysis Type ...................................................................................................................... 7–1
7.3. Setup Sub-Case ............................................................................................................................ 7–1
7.4. Write/View Input file ..................................................................................................................... 7–1
7.5. Submit Solver Run ........................................................................................................................ 7–1
7.6. Post Process Results ...................................................................................................................... 7–1
7.7. FEA Solver Support ....................................................................................................................... 7–1
vi ANSYS ICEM CFD/AI*Environment 10.0 User Manual . . ' SAS IP, Inc.
ANSYS ICEM CFD/AI*Environment 10.0 User Manual
List of Figures
1.1. Close Hole .......................................................................................................................................... 1–2
1.2. After closing the hole .......................................................................................................................... 1–2
1.3. Before Remove Holes .......................................................................................................................... 1–3
1.4. After Remove Holes ............................................................................................................................ 1–3
1.5. Geometry with a gap .......................................................................................................................... 1–4
1.6. Result with Close Gap > Fill ................................................................................................................. 1–4
1.7. Result with Close Gap > Trim ............................................................................................................... 1–5
1.8. Result with Close Gap > Blend ............................................................................................................. 1–5
1.9. Geometry with mismatched edges ...................................................................................................... 1–6
1.10. Geometry after match edges ............................................................................................................. 1–7
2.1. Curves and Points representing the sharp edges and corners ............................................................... 2–3
2.2. Mesh with Curves and points .............................................................................................................. 2–4
2.3. Mesh without curves and points ......................................................................................................... 2–4
2.4. Geometry Input to Tetra ..................................................................................................................... 2–6
2.5. Full Tetra enclosing the geometry ....................................................................................................... 2–7
2.6. Full Tetra enclosing the geometry (In wire frame node) ....................................................................... 2–8
2.7. Cross-section of the Tetra to show how Tetra are fit in around geometry .............................................. 2–9
2.8. Mesh after it captures surfaces and separation of useful volume ........................................................ 2–10
2.9. Final Mesh before smoothing ............................................................................................................ 2–11
2.10. Final Mesh after smoothing ............................................................................................................. 2–12
2.11. Non-Manifold Vertices .................................................................................................................... 2–16
2.12. Quality Histogram ........................................................................................................................... 2–16
3.1. Initial block, block with O-Grid, O-Grid with include a face ................................................................... 3–5
6.1. Elements on Curve .............................................................................................................................. 6–1
6.2. Force Distribution as per the FEA concepts .......................................................................................... 6–2
6.3. Quadratic Element Nodes position ...................................................................................................... 6–3
6.4. Load Distribution as per the FEA concepts ........................................................................................... 6–4
6.5. QUAD9 Element ................................................................................................................................. 6–5
ANSYS ICEM CFD/AI*Environment 10.0 User Manual . . ' SAS IP, Inc. vii
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Chapter 1: CAD Repair
Before generating the Shell/Tetra mesh, the user should confirm that the geometry is free of any flaws that
would inhibit optimal mesh creation. If the user wishes to save the changes in the native CAD files, the following
checks should be performed in a direct CAD interface.
To create a mesh, Tetra requires that the model contains a closed volume. If there are any holes (gaps or missing
surfaces) in the geometry that are larger than the local tetras, Tetra will be unable to find a closed volume. Thus,
if the user notices any holes in the model prior to mesh generation, he or she should fix the surface data to
eliminate these holes.
The Build Topology operation will find holes and gaps in the geometry. It should give yellow curves where there
are large (in relation to a user-specified tolerance) gaps or missing surfaces.
During the Tetra process any leakage path (indicating a hole or gap in the model) will be indicated to the user.
The problem can be corrected on a mesh level, or the geometry in that vicinity can be repaired and the meshing
process repeated. For further information on the process of interactively closing holes, see the section Tetra >
Tetra Generation Steps > Useful Region of Mesh.
For more useful information on CAD Repair topics, please go to http://www-berkeley.ansys.com/faq/faq_top-
ic_8.html.
1.1. How are Close Holes and Remove Holes different?
1.1.1. Close Holes
Use Close Holes if the hole is bounded by more than one surface. For example, look at Figure 1-1 below. The
yellow curves represent the boundary of the hole. From the figure it is clear that this hole is bounded by more
than one surface. Figure 1-2 shows the geometry after Close Holes is completed. A new surface is created to
close the hole.
ANSYS ICEM CFD/AI*Environment 10.0 User Manual . . ' SAS IP, Inc.
Chapter 1: CAD Repair
Figure 1.1 Close Hole
Figure 1.2 After closing the hole
1.1.2. Remove Holes
Use Remove Holes if the hole lies entirely within a single surface, such as a trimmed surface. For example, look
at Figure 1-3. The two yellow curve loops represent the boundaries of the holes, which lie entirely in one surface.
Figure 1-4 shows the geometry after Remove Holes is completed for one of the holes. The existing surface is
modified by removing the trim definition.
1–2 ANSYS ICEM CFD/AI*Environment 10.0 User Manual . . ' SAS IP, Inc.