VSP File Types & VSP Meshing

Transcription

1 VSP File Types & VSP Meshing Rob McDonald Cal Poly VSP Workshop August 23, 2012

2 VSP Input Representations Input Parametric geometry (vsp) Background image (jpg) Surface textures (tga, jpg) Automation script (txt) Airfoil definition (af) Fuselage section definition (fxs) Cabin definition (cab) Wireframe as mesh (hrm) Wireframe as surfaces (hrm) Triangulated mesh (stl, NASCART) Vorlax case file (cas) Coming soon Design file (des, xdes, XDDM) 2

3 VSP Output Representations Output Parametric geometry (vsp) Screen capture (jpg) Automation script (txt) Wetted area/volume report (txt, csv) Drag buildup report (tsv) Area ruling report (txt) Mass properties report (txt) Wireframe (hrm) X3D 3D Web model (x3d) Felisa (fel) Untrimmed surfaces (3dm) Trimmed surfaces (srf) Unintersected triangulated components (tri, possibly others) Intersected triangulated components (stl, NASCART, tri, msh, pov) Isotropic triangulated surface mesh (stl, poly, tri, obj, msh, NASCART) Structural mesh (stl, NASTRAN, Calculix) Vorlax case file (cas) Vorlax geometry & input (inp) Coming soon Design file (des, xdes, XDDM) 3

4 Paths to Cart3D Quadrilateral Wireframe Export CART3d File (.tri) Unintersected Triangle Wireframe CompGeom Export CART3d File (.tri) CFD Mesh Output.tri Bicubic Bezier Surface Cart3D intersect Intersected Triangle Wireframe Triangle Mesh 4

5 Paths to Cart3D Quadrilateral Wireframe Export CART3d File (.tri) Unintersected Triangle Wireframe CompGeom Export CART3d File (.tri) CFD Mesh Output.tri Bicubic Bezier Surface Cart3D intersect Intersected Triangle Wireframe Triangle Mesh 5

6 Unintersected Triangle Wireframe Intersected Triangle Wireframe Quadrilateral Wireframe Triangle Mesh 6

7 Pros / Cons of Paths Unintersected CompGeom CFD Mesh Pros Speed Cons Robustness Derivatives with design framework Robustness Coincident faces Nacelles Extra step Pros Speed Cons Robustness Special cases Robustness Recommended for Today Pros Triangle Quality Cons Special cases Robustness 7

8 Export Unintersected (before)

9 Export Unintersected (after) 9

10 Execute CompGeom (before)

11 Execute CompGeom (after) 1 11

12 Export CompGeom

13 Practice Session Unintersected CompGeom Save for Cart3D tutorial Resolution Effects (quads to triangles directly) Num Pts Num XSecs 13

14 CFD Mesh Generator 14

15 CFD Mesh Surface mesh generator Isotropic triangles (no stretching) Bicubic Bezier surfaces Bezier intersection curves Sourcing control Curvature control Optional wakes Optional half-models Preferred for most CFD tools CBAero TetGen AFLR3 VLE 15

16 Local Radius of Curvature r Greatest Principal Normal Curvature r = 1 k 16

17 Curvature Meshing Criteria Max Gap Num Circle Segments g l l Num Circle Segments = 8 $ & l = % '& r > g; 2 2! r! g " g 2 r # g; 2! g # % l = $ % & N > 2; N " 2; r! 2!sin(! N ) r! 4 N 17

18 Growth Ratio Limiter Growth Ratio X Limits length of next edge to ratio of current edge. 18

19 Source Types Point Line Box 19

20 Sourcing Attached to components (u, w) Size in model units (length) Sphere of influence (radius) 20

21 Mesh Criteria Precedence Smallest Edge Across Criteria Subject to Constraints Above & Below Sources Max Edge Len Growth Ratio Max Gap Num Circle Segments Min Edge Len 21

22 Turning Mesh Criteria OFF Sometimes it is useful to turn a mesh criteria OFF. Criteria Direction Value Scaled? Max Edge Len large (scaled) Growth Ratio large 10.0 Sources none Max Gap large 10.0 (scaled) Num Circle Segments small Min Edge Len small (scaled) Max = Min will turn OFF Max Gap & Num Circle Segments Sources Max Edge Len Growth Ratio Max Gap Num Circle Segments Min Edge Len 22

23 Meshing Strategy 1. Set Max based on model dimensions Set Min = Max (turning off MG and NCS) No Sources Adjust Max & Min until satisfied (uniform coarsest) 2. Set Min to smaller value Say Min = Max/20 3. Choose MG or NCS as preferred curvature parameter (CP) Set other curvature parameter (OCP) OFF Adjust CP until satisfied Adjust Min as required (are smallest edges small enough?) 4. Adjust OCP (optional) 5. Add mesh sources as required Resolve flow features 23

24 Top Model Constant curvature (constant radius) Increasing curvature (decreasing radius) Extreme curvature (vanishing radius) 24

25 CFD Mesh GUI 25

26 Global Global Source Adjustment Global & Curvature Meshing Criteria Half Mesh Switch TetGen Far Field Mesh Output Go Button 26

27 Display Source Display Switch Mesh Display Switch Mesh Output Go Button 27

28 Output File Output Switches File Paths File Browser Button Mesh Output Go Button 28

29 Sources Component Chooser Add Default Button Source Type Chooser Component Source List Add/Delete Buttons Individual Source Editor Mesh Output Go Button 29

30 Wakes Wake Length Wake Angle Component Chooser Wake Switch Mesh Output Go Button 30

31 Practice Session CFD Mesh Top model Experiment with meshing parameters Turn all criteria off play with one at a time Follow meshing strategy Resolution Effects (quads to bicubic Bezier patches) Num Pts Num XSecs Computational cost (Build Target Map) CFD Mesh Your model Follow meshing strategy 31

32 Command Line Unintersected: vsp batch airplane.vsp tri CompGeom: vsp batch airplane.vsp compgeom tri CFD Mesh: vsp batch airplane.vsp cfdmesh 1.0 (1.0 is refinement factor) Each command will output corresponding airplane.tri. 32