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12 th International Meshing Roundtable Panel Discussion

12 th International Meshing Roundtable Panel Discussion. Darby Vicker darby.vicker@nasa.gov 281-483-6107 September 16, 2003. Background. NASA/JSC/EG3 – Applied Aeroscience and Computational Fluid Dynamics (CFD) Branch Typical uses of CFD in our branch include

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12 th International Meshing Roundtable Panel Discussion

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  1. 12th International Meshing RoundtablePanel Discussion Darby Vicker darby.vicker@nasa.gov 281-483-6107 September 16, 2003

  2. 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

  3. 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

  4. 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

  5. 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

  6. Mesh Quality • Triangulated grid in high curvature • Wing leading edge example

  7. 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;

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