12th International Meshing Roundtable Panel Discussion

1
12th International Meshing RoundtablePanel
Discussion

• Darby Vicker
• darby.vicker_at_nasa.gov
• 281-483-6107
• September 16, 2003

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Background

• NASA/JSC/EG3 Applied Aeroscience and
  Computational Fluid Dynamics (CFD) Branch
• Typical uses of CFD in our branch include
• Aero databases stability and trajectory
  analysis
• Calibration of flight instruments X-38 FADS
• Separation models X-38/B-52
• Verification of engineering analysis
• Complete flow fields for debris analysis and flow
  feature extraction

X-38 FADS
SSLV Reynaldo Gomez
X-38/B-52 James Greathouse
High Fidelity X-38 Darby Vicker
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CFD Tools in EG3

• Two primary codes
• OVERFLOW Navier-Stokes solver
• Requires chimera overset structured volume grids
• CART3D Euler solver
• Requires triangulated surface grids (geometry
  definition only)
• Automatic volume grids via sub-divided Cartesian
  grids
• Automation is important
• CFD is becoming more accepted and relied upon as
  an analysis tool
• The frequency and number of requested solutions
  is increasing
• EG3 has been asked to produce 150 SSLV CFD
  solutions on a 33 million grid-point system for
  one of the return-to-flight tasks
• Makes automation of the complete CFD process,
  including grid generation, essential
• SSLV elevon and body flap automation animation

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Chimera Grid Generation

• Structured grids that arbitrarily overlap
• Quick turn around from grid generation to
  solutions
• Possible to grid complex geometry with
  structured grids in a relatively short time
• Flow solvers available are very efficient

SSLV External Tank Solid Rocket Boosters
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CAD

• Getting a quality representation of geometry
  ready for grid generation is not trivial
• We receive geometry from many CAD platforms
  (ProEngineer, CATIA, Unigraphics, etc.)
• For complex geometry, there are often undesirable
  features
• Slivers, gaps, highly warped or twisted surfaces,
  etc.
• Currently we rely on 3rd party software to fix
  geometry problems and (usually) translate to a
  neutral format

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Mesh Quality

• Triangulated grid in high curvature
• Wing leading edge example

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Desirable Software Features

• Batch mode operation
• Easily accessible feature information
• Vertex location, arc length, surface area, etc.
• Grid diagnostics
• Tabulated numbers and graphical indication of
  open edges, non-manifold edges, etc.
• Improved (structured) surface grid creation via
  extrusion
• Ease of use
• Robustness
• Variety of boundary conditions
• Basic float periodic splay constant X, Y or Z
• Advanced Follow u or v of CAD patch follow a
  curve follow exact points on a curve