CAD/CAE Data Exchange and Geometry Cleanup (Virtual Geometry)IntroductionCAD Data Exchange - Direct OptionsCAD Data Exchange - Standard OptionsCAD Data Exchange - Standard Options (2)Import Mesh and Import CADCheck and Heal Real GeometryVirtual GeometryVirtual Geometry: UsesCreating Virtual GeometryCharacteristicsVirtual Geometry Operations-1Virtual Geometry Operations-2Virtual Geometry Operations-3PowerPoint PresentationSlide 16Slide 17T-Junctions OptionComparison of Face Unite, Merge, and ConnectImporting IGES FilesVirtual Geometry Cleanup Strategy-1Virtual Geometry Cleanup Strategy-2© Fluent Inc. 01/14/197-1 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comCAD/CAE Data Exchangeand Geometry Cleanup(Virtual Geometry)© Fluent Inc. 01/14/197-2 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comIntroductionSeveral translation methods available to enable data exchange with CAD/CAE systems.Appropriate approach depends upon source.Translation can:return incomplete, corrupt, or disconnected geometryreturn geometry details unnecessary for CFD analysisGeometry cleanup refers to processes required to prepare geometry for meshing.Fix incomplete or corrupt geometry and connect disconnected geometryRemove unnecessary detailsDecompose geometry into meshable sectionsGambit’s Virtual Geometry operations can help with the cleanup process.© Fluent Inc. 01/14/197-3 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comCAD Data Exchange - Direct OptionsDirect Translation OptionsACIS-based CAD programs:e.g., AutoCad, Cadkey, TurboCadcan export ACIS files (.sat or .sab) which can be imported into Gambit.Parasolids-based CAD programs:e.g., Unigraphics, SolidWorks, PATRAN, ANSYScan export Parasolid files (.x_t and .xmt_txt) which can be imported into Gambit.CAD programs using proprietary geometry kernele.g., I-DEAS, Catia, Pro-Engineer, CADDSDirect (single-stage) translators purchase from third party vendore.g., Catia/ACIS translatorsee spatial.com website for more information© Fluent Inc. 01/14/197-4 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comCAD Data Exchange - Standard OptionsStandard Translation OptionsTranslation uses an intermediate, neutral or standard, file format.Applicable for all CAD/CAE systemsthat can output:STEP filesPro/E supports STEP export at no additional cost.Other systems support STEP as add-on.IGES filesCommon format supported by most systems.STEP (Standard for Exchange of Product model data)International standard defining format for geometry and model information.Gambit supports AP203 and AP214Preferred over IGES import© Fluent Inc. 01/14/197-5 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comCAD Data Exchange - Standard Options (2)Standard Translation Options (continued)IGES (Initial Graphics Exchange Specification)Topology/connectivity information is lost when CAD programs export IGES surface data only.e.g., faces associated with volume, etc.implies that volumes must be recreated from imported faces (tedious)Some CAD packages export IGES-solids as well as IGES-surfaces.I-DEAS and CADDSTopology/connectivity information maintained.Gambit provides two options for IGES importSpatial–Imported geometry comes in as all real, supports solidsNative (Fluent)–Original IGES translator, does not support solids–Trimmed surfaces come in as virtual geometry© Fluent Inc. 01/14/197-6 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comImport Mesh and Import CADImport Mesh and some Import CAD options result in faceted geometry.Least preferred approachImport/CAD Pro/E (Direct)Gambit directly accesses Pro/E’s geometry engineEliminates geometry translation lossesUser works in Gambit environmentNeed special Gambit and valid Pro/E licenseSolid models alone are supportedassemblies are not© Fluent Inc. 01/14/197-7 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comGeometry imported from other CAD systems can lack the required accuracy and precision to render valid or connected ACIS geometry.This results from numerical limitations in original CAD system or neutral file formats, or differences in tolerances between CAD systems and ACIS.Use visual inspection and check command to verify integrity of geometry/topology.Fix geometry problems by healing if real geometry.Healing can be invoked at time of import.Fix topology problems by deleting and reconstructing entities with virtual geometry.Connect disconnected geometry using healer or virtual geometry operations.Healing corrects tolerance problems in the model and attempts to connect coincident edges and form volume from connected faces.If unsuccessful, resort to virtual geometry operations.Check and Heal Real Geometry© Fluent Inc. 01/14/197-8 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comVirtual GeometryThree kinds of geometry in GAMBIT:RealDefined by the ACIS library of geometry creation/modification routines.Geometry defined by mathematical formulae.VirtualA Fluent Inc. library of routines providing additional functionality by redefining topology.Derive their geometrical descriptions by references to one or more real entities (called the Hosts).Faceted geometryTreated like virtual geometry.Derived from importing a mesh or faceted geometry into GAMBIT, split mesh operations, or stairstep meshing scheme.Two objects that share the same underlying geometry but different topologies.© Fluent Inc. 01/14/197-9 Introductory GAMBIT Notes GAMBIT v2.0 Jan 2002Fluent User Services Centerwww.fluentusers.comVirtual Geometry: UsesVirtual geometry and the operations that create them are used to simplify, clean, and connect existing geometry.Simplify/Clean:remove details from the model unnecessary for CFD analysis.merge faces/edges to increase mesh quality.decompose geometry into smaller, meshable components.Connect:Connect geometry that becomes disconnected during import process.Virtual geometry