Samuel H. Huang, J. Shi

1
Automatic Generation of Quadrilateral Multi-Block
Topology for FEA/CFD Applications

• Samuel H. Huang, J. Shi
• University of Cincinnati
• Sumit Maloo
• Hauenstein Burmeister
• Erlendur Steinthorsson
• Parker Hannifin

2
Agenda

• Introduction
• Adaptive Knowledge Discovery
• Methodology
• Prototype Software Tool
• Conclusion

3
Introduction

• Mesh generation is a critical starting point for
  FEA/CFD
• Lower quality tetrahedral meshes can be generated
  semi-automatically
• Higher quality hexahedral meshes require
  significant human effort to generate
• Experts can generate better quality meshes faster
  than non-experts

4
Objective

• Computerize human expertise to automatically
  generate hexahedral mesh
• Focusing on 2-Dimensional geometry (quadrilateral
  meshes)
• Use multi-block mesh generation strategy
• Extract rules for block creation
• Create multi-block topology
• Interface with commercial software tools (GridPro
  az3000) to generate final meshes

5
Adaptive Knowledge Discovery
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Uniques Features

• General systems framework that can be applied in
  various domains with minimum or no adjustment
• Transparent knowledge representation conducive to
  shortening the learning curves
• Self-improving capability to adjust to a changing
  environment
• Reduced time and effort in knowledge
  acquisition/process modeling

7
Methodology
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Boundary Rules
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Bisect, Project, and Merge Rules

• Separate part geometry into two roughly equal
  parts (in terms of size, shape and number of
  vertices)
• Project vertices that are associate with a large
  angle (greater than 90?) to the bisector line
  without intersecting other edges and creating
  triangles
• Merge two projection points if they are from
  different side of the geometry are close to each
  other

10
Refinement Rules (General)
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Refinement Rules (Polygon)
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Examples (Boundary and Bisect)
A
B
13
Examples (Project, Merge and Refine)
A
B
14
Examples (Topology and Mesh)
A
B
15
Prototype Software Tool

• Implemented using Microsoft Visual C
• Contains over ten thousands lines of codes
• Use AutoCAD as front end CAD system (geometry
  stored in DXF format)
• Modular functionality to allow flexible user
  interaction (also includes one-click multi-block
  generation)
• Generates TIL (topology input language) codes to
  describe multi-block topology
• Export to GridPro az3000 to generate the final
  mesh

16
Software Snapshot
Import Geometry
Automation Wizard
Create Boundary
Projection
Merge
Check Loop
Add Surface
Remove Surface
Export TIL Codes
17
Illustrative Example (Topology)
18
Illustrative Example (Mesh)
19
Illustrative Example (Close Up)
Separate Surfaces
Same Surface
20
Conclusion

• Established the feasibility of automating the
  process of generating high quality meshes
• Methodology can be generalized to create
  multi-block for 3-Dimensional geometry
• Implementation requires significant resources
• Geometry recognition (depends on front end CAD
  system)
• Hundreds of thousands lines of codes are expected