FluentGambit提示和技巧教程2001UGMGambitTipsTricks

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1、 Fluent Inc.9/29/20221Fluent Software TrainingUGM 20012001 UGM Gambit:Tips&TricksJune 4,2001Shyam Kishor Fluent Inc.9/29/20222Fluent Software TrainingUGM 2001OutlineuData exchange with other CAD/CAE systemsuClean-up and Construction strategiesuUseful TipsuNew Features of Gambit 2.0 Fluent Inc.9/29/2

2、0223Fluent Software TrainingUGM 2001Data exchange with other CAD/CAE systemsuDirect optionsuStandard-based optionsuImporting meshes and faceted geometryuCAD-to-Gambit flowchart summaries Fluent Inc.9/29/20224Fluent Software TrainingUGM 2001Direct Options-1uACIS-based CAD programs:le.g.,AutoCAD,Cadke

3、y,TurboCadlCan export ACIS files(.sat or.sab)which can be imported into Gambit.nACIS version compatibilitysGambit typically employs recent ACIS rev.(ACIS 6.3 for Gambit 2.0)sGambit can import and export older versions of ACIS.uParasolid-based CAD programs:le.g.,Unigraphics,SolidWorks,Solid Edge,PATR

4、AN,ANSYSlCan export Parasolid files(.x_t&.xmt_txt)which can be imported into GambitnParasolid version compatibilitysGambit can import and export most versions up through 11.1 Fluent Inc.9/29/20225Fluent Software TrainingUGM 2001Direct Options-2uDirect(single-stage)translators for native CAD systemsl

5、e.g.,Pro-E/ACIS,Catia/ACISlAvailable from various vendors(see http:/ for full listing)Fluent Inc.9/29/20226Fluent Software TrainingUGM 2001Standard-based OptionsuUse of neutral file format to exchange datalSTEPlIGES Fluent Inc.9/29/20227Fluent Software TrainingUGM 2001Data exchange via STEPuSTEP(STa

6、ndard for the Exchange of Product model data):lInternational standard that defines a neutral file format for the exchange of geometric,topologic,and annotation data.lMost CAD programs include STEP exportnPro/ENGINEER at no additional costnMost others as an add onlBoth STEP AP203 and STEP AP214 are s

7、upported by GambitlBetter than IGESnSTEP supports solid modelssCreates real Gambit(ACIS)volumes after import.nTopology/connectivity-related information is maintained lSTEP export nExports real geometry,including solid volumes Fluent Inc.9/29/20228Fluent Software TrainingUGM 2001Data exchange via IGE

8、SuIGES(Initial Graphics Exchange Specification)Files:lMost CAD programs can export IGES files.nTopology/connectivity information is lost when CAD programs export IGES surface data only.nSome CAD packages export IGES-solids as well as IGES-surfaces.sI-DEAS and CADDSsTopology/connectivity information

9、maintained.lGambit provides two options for IGES importnSpatial sCreates real geometry sSupports IGES-solids(MSBO)nNative sCreates virtual geometry for trimmed surfacessSupports surfaces onlysUse only as a fallback when Spatial translator failslIGES export sExports real geometrysSupports IGES solids

10、(MSBO)Fluent Inc.9/29/20229Fluent Software TrainingUGM 2001STEP/Parasolid-to-Gambit FlowchartReal GeometryGeometry ImportCheck GeometryOkay?Connected?HealNoYesNoYesCheck GeometryHealConnected?Use Virtual GeometryBetter?YesNoNo(undo)YesSTEP/Parasolid Fluent Inc.9/29/202210Fluent Software TrainingUGM

11、2001IGES-to-Gambit FlowchartReal GeometrySpatial TranslatorIGESNative TranslatorOkay?Check GeometryOkay?Connected?HealNoYesNoYesCheck GeometryHealConnected?Use Virtual GeometryBetter?YesNoNo(undo)YesNoYes Fluent Inc.9/29/202211Fluent Software TrainingUGM 2001Data exchange via Mesh/Faceted Geometry-1

12、lImport of mesh or faceted geometry files results in faceted geometrylSupported Mesh Formats Faceted Geometry FormatsnFLUENT4l I-DEAS FTLnFLUENT5l Optegra VisualizernTGRIDl STL nFIDAPnGAMBITnI-DEAS UNV(Universal format)nANSYS nPLOT3D(Formatted)nNASTRANnPATRANnHYPERMESH Fluent Inc.9/29/202212Fluent S

13、oftware TrainingUGM 2001Data exchange via Mesh/Faceted Geometry-2lPLOT3D files with Iblanking and/or of binary typenUse tfilter fe2ram from an operating system command prompt to first convert it to a Fluent/Fidap mesh filenImport the resulting mesh in Gambit.lImport of Mesh with hanging nodes is not

14、 supportedlMesh FilesnBoundary types are not preserved during import.nGenerates faceted geometry from surface or volume mesh import.nUse Virtual Geometry operations to work with entities.nConvert virtual geometry to real if needed.lFaceted Geometry FilesnSimilar to mesh but defining triangles unsuit

15、able for meshingnSTL lacks zone groupingsUse Feature Angle to separate facessWorks well for well-defined edges;otherwise use as last resort.Fluent Inc.9/29/202213Fluent Software TrainingUGM 2001CAD-to-Gambit Flowchart SummariesuIn general,translation options listed in order of decreasing preference(

16、left to right).uSome options require third party translator software.uBest translation path depends on quality of CAD data(model).Fluent Inc.9/29/202214Fluent Software TrainingUGM 2001Pro/E-to-Gambit FlowchartPro/EngineerGambitDirect(STEP)Direct TranslatorSTEPOptegra VisualizerMeshSTL(real geometry)

17、(faceted geometry)IGES*IGES native may produce virtual geometryACISDirect Integration of Pro/E with Gambit 2.0 Fluent Inc.9/29/202215Fluent Software TrainingUGM 2001Catia-to-Gambit FlowchartCatiaGambitIGES Solids(AIX only)Catia-ACIS TranslatorSTEPIGES Surfaces*MeshSTLACIS(real geometry)(faceted geom

18、etry)*IGES native may produce virtual geometry Fluent Inc.9/29/202216Fluent Software TrainingUGM 2001I-DEAS-to-Gambit FlowchartI-DEASGambitIGES*MSBOSTEPFaceted Part File(FTL)MeshSTL(real geometry)(faceted geometry)*IGES native may produce virtual geometry Fluent Inc.9/29/202217Fluent Software Traini

19、ngUGM 2001Unigraphics-to-Gambit FlowchartUnigraphicsGambitSTEPUnigraphics-ACIS Trans.ParasolidIGES*MeshSTLACIS(real geometry)(faceted geometry)*IGES native may produce virtual geometry Fluent Inc.9/29/202218Fluent Software TrainingUGM 2001SolidWorks-to-Gambit FlowchartSolidWorksGambitSTEPIGES*MeshST

20、LACIS(real geometry)(faceted geometry)Direct ACIS ExportParasolid*IGES native may produce virtual geometry Fluent Inc.9/29/202219Fluent Software TrainingUGM 2001CADDS-to-Gambit FlowchartCADDSGambitIGES*CADDS-ACIS TranslatorSTEPMeshSTLACIS(real geometry)(faceted geometry)*IGES native may produce virt

21、ual geometry Fluent Inc.9/29/202220Fluent Software TrainingUGM 2001OutlineuData exchange with other CAD/CAE systemsuClean-up and Construction strategiesuUseful TipsuNew Features of Gambit 2.0 Fluent Inc.9/29/202221Fluent Software TrainingUGM 2001Typical Cleanup Procedure for Imported DatalDelete unn

22、ecessary geometrylCheck validity of the geometry(visual+check commands)lCorrect invalid geometry(Healing and/or reconstruction)lCheck connectivity by color codinglEliminate short edgeslCheck connectivitylCreate additional geometry and form volumelSimplify/edit edges,faces,volumeslDecompose volume,if

23、 necessarylMesh the geometrylPlan aheadnSome operations will not work with virtual geometry(booleans,sweeps except edges,revolves,certain splits)nPostpone operations that create virtual entities.Fluent Inc.9/29/202222Fluent Software TrainingUGM 2001Check Real GeometryuChecks for geometrical and topo

24、logical inconsistencies.lTopology problems must be fixed before meshinglGeometry not C1,C2,G1or G2nIndicates lack of parametric/geometric continuitynOperations like real booleans,splits and sweeps may failsUse virtual splits as fallbacknDo not prevent meshinglFix real geometry problems by healing an

25、d/or by regenerating entitieslFix topology and virtual/faceted geometry problems by deleting(hiding)and reconstructing entities Fluent Inc.9/29/202223Fluent Software TrainingUGM 2001Typical Cleanup Procedure for Imported DatalDelete unnecessary geometrylCheck validity of the geometry(visual+check co

26、mmands)lCorrect invalid geometry(Healing and/or reconstruction)lCheck connectivity by color codinglEliminate short edgeslCheck connectivitylCreate additional geometry and form volumelSimplify/edit edges,faces,volumeslDecompose volume,if necessarylMesh the geometrylPlan aheadnSome operations will not

27、 work with virtual geometry(booleans,sweeps except edges,revolves,certain splits)nPostpone operations that create virtual entities.Fluent Inc.9/29/202224Fluent Software TrainingUGM 2001Healing Real Geometry-1uHealing is designed to detect and correct accuracy problems in ACIS modelsuACIS(geometry ke

28、rnel of Gambit),a high precision modeler,needs all entities to satisfy stringent data integrity checksuGeometry imported from other CAD systems often lacks the required accuracy&precision due to:lInherent numerical limitations in the original CAD systemlLimitations of data transfer through neutral f

29、ile formatslDifferences in tolerance settings between the original CAD system and Gambitu Three phases of Healing process:lGeometry simplification lStitching lGeometry building Fluent Inc.9/29/202225Fluent Software TrainingUGM 2001Healing Real Geometry-2uGeometry simplificationlConverts spline surfa

30、ces to corresponding analytic forms(e.g.,planes,cylinders,circular cones etc.)wherever possiblelResults in a reduction of data size&speed improvements in geometric operations.lGeometry simplification tolerancenWith tighter tolerance,only spline surfaces which are exact analytic surfaces get simplifi

31、ednWith relaxed tolerance,approximate analytic fits to spline surfaces are obtained.It may increase the gap between surfaces and healing in subsequent operations would be more difficultnThe default tolerance of 0.0001 should provide very good approximation in most caseslFor some cases,overall result

32、s may be better if simplification is disabled Fluent Inc.9/29/202226Fluent Software TrainingUGM 2001Healing Real Geometry-3uStitchinglStitch together the loose faces.lSimilar to volume stitch but can handle the gaps and does some geometry cleaning on the stitched data to handle small edges occurring

33、 in the body.l Main Characteristics:nHandles varying gapsnResolves multiple verticesnHandles small edgesnSplit edges appropriatelynEnsure consistent face normalslStitching tolerances:nIncremental stitching.nStarts with minimum tolerance and increases in steps towards maximum tolerancenMinimum tolera

34、nce must always be smaller than the length of the smallest edge in the modelnMaximum tolerance denotes the largest gap in the model.lThe result of stitching could give one or more acis volumes.Fluent Inc.9/29/202227Fluent Software TrainingUGM 2001Healing Real Geometry-4uStitching Fluent Inc.9/29/202

35、228Fluent Software TrainingUGM 2001Healing Real Geometry-5uGeometry BuildinglBuilds the geometry as necessary to correct the gaps&inaccuracies in the model.lImprove precision of face,edge,and vertex datalRecalculate the bad curves and points by recomputing intersections.Transversal Intersections:Gap

36、s are filled by extendingthe adjoining surfaces and recomputing the intersection Fluent Inc.9/29/202229Fluent Software TrainingUGM 2001Healing Real Geometry-6uGeometry BuildingTangential Intersection of AnalyticSurfaces:Surfaces are snapped to each otherusing linear transformationsTangential Interse

37、ction of SplineSurfaces:Correction via control points modification Fluent Inc.9/29/202230Fluent Software TrainingUGM 2001Typical Cleanup Procedure for Imported DatalDelete unnecessary geometrylCheck validity of the geometry(visual+check commands)lCorrect invalid geometry(Healing and/or reconstructio

38、n)lCheck connectivity by color codinglEliminate short edgeslCheck connectivitylCreate additional geometry and form volumelSimplify/edit edges,faces,volumeslDecompose volume,if necessarylMesh the geometrylPlan aheadnSome operations will not work with virtual geometry(booleans,sweeps except edges,revo

39、lves,certain splits)nPostpone operations that create virtual entities.Fluent Inc.9/29/202231Fluent Software TrainingUGM 2001Connecting edges provides connectivity between faces.This enables faces to be stitched together to form volume.Connect EdgeslNew option to preserve first edge shape during virt

40、ual edge connectlTypical Procedure:nSpecify Real and Virtual ConnectsReal connects attempted first.sSpecify initial Tolerance or Shortest Edge%sConnect on all edges.nRepeat above step with successively larger tolerances.nInclude T-junction option as final step.sInvoking too early may result in very

41、small edges.nForce Connect remaining disconnected edges.lFailure to stitch together volume will result in error message identifying problem edges.Fluent Inc.9/29/202232Fluent Software TrainingUGM 2001Connect Edges:TolerancesuTolerances used for connect should be much less than mesh size.lMesh within

42、 the tolerance region gets pushed back to edge.sFor faces separated by a large gap,create new face to fill the gap.sFor faces that overlap by large amount,split each face with the intruding edge and form new face in center.Tolerance used to connect edges to create two connected virtual faces.Faces o

43、verlappingFaces with gapFaces connected Fluent Inc.9/29/202233Fluent Software TrainingUGM 2001Connect Edges:T-Connect OptionuUsing T-Connect Option with relatively low tolerance can generate unwanted small edges.lUse Highlight Shortest Edge to check length before and after operation.lCan pick which

44、vertices are to be involved in edge splits in Vertex list box(default is all).Tolerance used to connect edges will account for small gaps but not the larger ones.Small edges formed as a result of improper use of T-Connect Option.Fluent Inc.9/29/202234Fluent Software TrainingUGM 2001Typical Cleanup P

45、rocedure for Imported DatalDelete unnecessary geometrylCheck validity of the geometry(visual+check commands)lCorrect invalid geometry(Healing and/or reconstruction)lCheck connectivity by color codinglEliminate short edgeslCheck connectivitylCreate additional geometry and form volumelSimplify/edit ed

46、ges,faces,volumeslDecompose volume,if necessarylMesh the geometrylPlan aheadnSome operations will not work with virtual geometry(booleans,sweeps except edges,revolves,certain splits)nPostpone operations that create virtual entities.Fluent Inc.9/29/202235Fluent Software TrainingUGM 2001Simplify/Edit

47、faceslEliminate sliver facesnMerge face with neighborsAvoid merging together connected faces that form a sharp angle(90).nMerge remaining edgeslEliminate sharp corners and anglesnSplit the face to isolate the bad anglenMerge the new face to an adjacent facenMerge the edgeslCollapse versus mergenMerg

48、e for similar faces and sliver facesnCollapse for symmetry,blends,fillets,etc.(collapse adds extra layer of topological information)lIf tolerance is larger than element size,or if element size is smaller than faces that were merged/collapsed,meshing may fail on merged surfaces Fluent Inc.9/29/202236

49、Fluent Software TrainingUGM 2001Virtual Cleanup During IGES ImportuAttempts virtual cleanup through automated sequence of Connects/Merges.lMerges edges based on length.nUsing merge tolerance.lMerges edges based on angle.ngeometry.edge.VIRTUAL_MERGE_MIN_ANGLElReal connects of vertices,edges,faces.lVi

50、rtual connects of vertices,edges,faces.nUsing connect tolerance.lEdge connects with T-Option.nIf any changes are made,repeats Virtual connect of edges,faces.lAttempts volume-stitch-virtual.lCan also be used after importsOpen the IGES Import formsClear the File Name fieldsClick Virtual Cleanup checkb

51、oxsClick Accept Fluent Inc.9/29/202237Fluent Software TrainingUGM 2001OutlineuData exchange with other CAD/CAE systemsuClean-up and Construction strategiesuUseful TipsuNew Features of Gambit 2.0 Fluent Inc.9/29/202238Fluent Software TrainingUGM 2001Geometry Tips-1lIf a particular boolean/split opera

52、tion fails to worknCould be due to complexity/quality of the model or due to difficulty in finding imprints of connected entitiessDisconnect the face/volume with adjacent entities by copying itsDelete the original face/volumesPerform the boolean/split on the copied entitysConnect them back before me

53、shinguUse alternative operations le.g.,an alternative to a split is:sGet intersection of tool and the target while retaining the targetsSubtract the result(intersection)from the target while retaining the toolsDo a connect nIf the tool is enclosed by the target,intersection of the two is not needed.

54、Fluent Inc.9/29/202239Fluent Software TrainingUGM 2001Geometry Tips-2uGambit 1.2.0&higher support booleans of multiple entities(faces/volumes)in one steplUse intersection/subtraction option to split one entity with multiple entitiesuOccasionally,real volume stitch may produce unwanted edge splitslAC

55、IS-specific problem(incorrect topology being generated)lUse Heal Faces in place of volume stitch command to create the volumelMay need to disconnect the faces if connected to other entitieslReconnect them before meshing lVirtual volume stitch can also be used Fluent Inc.9/29/202240Fluent Software Tr

56、ainingUGM 2001Geometry Tips-3lTo create real face by wireframe on noncoplanar surface,use a set of 3 or 4 edges per facelUse alternative methods of face creation(e.g.,net surface)wherever applicablelNew face creation methods and face primitives are available with Gambit 1.2.0 and higherlCombine prim

57、itives,booleans and bottom-up tools for faster model building Fluent Inc.9/29/202241Fluent Software TrainingUGM 2001Meshing Tips-1 uVertex types may be changed for Boundary Layers onlyuAllows desired BL creation in regions near vertices while maintaining desired face or volume meshing scheme Example

58、:Meshing a circular face with Map(square topology)and boundary layersVertex types=End,for mesh schemeVertex types=Side,for boundary layers Fluent Inc.9/29/202242Fluent Software TrainingUGM 2001Meshing Tips-2 Poor mesh by mapper on highly curved surface Projection to the surface distorts the mesh Lim

59、itation of algorithm Smooth the face mesh by“winslow”to fix it Fluent Inc.9/29/202243Fluent Software TrainingUGM 2001Meshing Tips-3uFinal exact projection of mesh on the surfacenMay take long time or produce skewed elements on complex/bad spline surfacesnShould be turned off(using the default MESH.F

60、ACE.PROJECT_TO_SURFACE)nCheck the mesh to ensure desired accuracy of geometry representation Fluent Inc.9/29/202244Fluent Software TrainingUGM 2001Meshing Tips-4uNumber of triangles on a single face exceed the default limit(100,000)lIncrease the limit using the default MESH.TRIMESH.MAX_FACESlA value

61、 of-1 indicate no restrictionuIf there is a resource constraintlMesh the whole model in several partslMesh one part,export the mesh and then delete it but keep the surface mesh at the interface(for conformal mesh)lDo the same for each part.lMerge all the meshes with tfilter tmerge3d or by reading th

62、em in TgridlDuplicate nodes at the interface can be merged together either in Fluent 5 by fusing the zones or in Tgrid by merging the nodes.Fluent Inc.9/29/202245Fluent Software TrainingUGM 2001Parametric Study:Tips-1uTest the model for the most extreme values first.uAdvanced parameterization might

63、be needed to avoid bad cell aspect ratio/skewness.lExample:Edge mesh density as a function of distanceintervals(4+(INT($fact*($h2-$h1)Fluent Inc.9/29/202246Fluent Software TrainingUGM 2001Parametric Study:Tips-2uUse mapped mesh when parameters have large variation span,since mesh can be stretched wi

64、thout severe distortion(compared to paved mesh).uUse different journal files for different parameter combinations.lExample:Pipe junction Pipe intersectionlThese are two topologically different models(3 faces,8 edges vs.2 faces,5 edges)uDo not use virtual mesh splits,since these are node-number depen

65、dent.Fluent Inc.9/29/202247Fluent Software TrainingUGM 2001OutlineuData exchange with other CAD/CAE systemsuClean-up and Construction strategiesuUseful TipsuNew Features of Gambit 2.0 Fluent Inc.9/29/202248Fluent Software TrainingUGM 2001New Features of Gambit 2.0uG/TurbouDirect Pro/E IntegrationuSi

66、ze FunctionuEnd User Customization(Dynamic GUI)uGeneral Meshing Enhancements(3d Boundary Layer,Mesh Link,Connect Preserving Mesh)uMesh Export UpgradeuGeneral Geometry EnhancementsuGeometry Kernel UpgradeuMiscellaneous Fluent Inc.9/29/202249Fluent Software TrainingUGM 2001G/TurbouAdd-on for automated preprocessing for turbomachineryuAutomated geometry construction and meshing for blade row modelslStarts from basic curve data defining blade,hub,and casing shapeslflexible meshingnstructured(H,H-C&H