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VSP File Types & VSP Meshing - PDF file VSP File Types & VSP Meshing. 2 VSP Input Representations • Input – Parametric geometry (vsp) – Background image (jpg) – Surface textures

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Text of VSP File Types & VSP Meshing - PDF file VSP File Types & VSP Meshing. 2 VSP Input...

  • Rob McDonald – Cal Poly

    VSP Workshop August 23, 2012

    VSP File Types & VSP Meshing

  • 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)

    http://www.openvsp.org/wiki/doku.php?id=representations

  • 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)

    •  Coming soon –  Design file (des, xdes, XDDM)

    –  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)

    http://www.openvsp.org/wiki/doku.php?id=representations

  • 4

    Paths to Cart3D Quadrilateral

    Wireframe

    Cart3D intersect

    CompGeom

    Export… CART3d File (.tri)

    Export… CART3d File (.tri)

    Unintersected Triangle

    Wireframe

    Triangle Mesh

    Intersected Triangle

    Wireframe

    CFD Mesh Output .tri

    Bicubic Bezier

    Surface

  • 5

    Paths to Cart3D Quadrilateral

    Wireframe

    Cart3D intersect

    CompGeom

    Export… CART3d File (.tri)

    Export… CART3d File (.tri)

    Unintersected Triangle

    Wireframe

    Triangle Mesh

    Intersected Triangle

    Wireframe

    CFD Mesh Output .tri

    Bicubic Bezier

    Surface

  • 6

    Quadrilateral Wireframe

    Unintersected Triangle

    Wireframe

    Triangle Mesh

    Intersected Triangle

    Wireframe

  • 7

    Recommended for Today

    Pros / Cons of Paths

    •  Pros –  Speed –  Robustness –  Derivatives with

    design framework

    •  Cons –  Robustness

    •  Coincident faces •  Nacelles

    –  Extra step

    Unintersected

    •  Pros –  Speed –  Robustness –  Special cases

    •  Cons –  Robustness

    •  Pros –  Triangle Quality –  Special cases

    •  Cons –  Robustness

    CompGeom CFD Mesh

  • 8

    Export Unintersected (before) 1

    2

    3

    4 5

  • 9

    Export Unintersected (after)

  • 10

    Execute CompGeom (before) 1

    2

    3

  • 11

    Execute CompGeom (after)

    1

  • 12

    Export CompGeom 1

    2

    3

    4 5

  • 13

    Practice Session •  Unintersected

    •  CompGeom –  Save for Cart3D tutorial

    •  Resolution Effects (quads to triangles directly) –  Num Pts –  Num XSecs

  • 14

    CFD Mesh Generator

  • 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

  • 16

    Local Radius of Curvature

    Greatest Principal Normal Curvature r = 1k

    r

  • 17

    Curvature Meshing Criteria

    l = N > 2; r !2 !sin ! N( ) N " 2; r ! 4 N

    #

    $ %

    & %

    l = r > g; 2 2 ! r ! g" g 2

    r # g; 2 ! g

    $ % &

    '&

    g

    l

    l

    Num Circle Segments = 8

    Max Gap Num Circle Segments

  • 18

    Growth Ratio Limiter

    0 2 4 6 8 10

    1

    1.2

    1.4

    1.6

    1.8

    2

    X

    G ro

    w th

    R at

    io

    Limits length of next edge to ratio of current edge.

  • 19

    Source Types Point Line Box

  • 20

    Sourcing

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

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    Mesh Criteria Precedence

    Max Gap Num Circle Segments

    Min Edge Len

    Max Edge Len

    Sources

    Growth Ratio

    Smallest Edge Across Criteria

    Subject to Constraints

    Above & Below

  • 22

    Turning Mesh Criteria ‘OFF’

    Criteria Direction Value Scaled? Max Edge Len large 100.0 (scaled) Growth Ratio large 10.0 Sources none Max Gap large 10.0 (scaled) Num Circle Segments small 0.00001 Min Edge Len small 0.000001 (scaled)

    Sometimes it is useful to turn a mesh criteria ‘OFF’.

    Max = Min will turn ‘OFF’ Max Gap &

    Num Circle Segments Max Gap Num Circle Segments

    Min Edge Len

    Max Edge Len

    Sources

    Growth Ratio

  • 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

  • 24

    ‘Top’ Model

    http://hangar.openvsp.org/vspfiles/106

    Constant curvature (constant radius)

    Increasing curvature (decreasing radius)

    Extreme curvature (vanishing radius)

  • 25

    CFD Mesh GUI

  • 26

    Global Global Source Adjustment

    Global & Curvature Meshing Criteria

    Half Mesh Switch

    TetGen Far Field

    Mesh Output

    ‘Go’ Button

  • 27

    Display Source Display Switch

    Mesh Display Switch

    Mesh Output

    ‘Go’ Button

  • 28

    Output File Output Switches

    Mesh Output

    ‘Go’ Button

    File Paths

    File Browser Button

  • 29

    Sources Component Chooser

    Add Default Button

    Source Type Chooser

    Add/Delete Buttons

    Mesh Output

    ‘Go’ Button

    Component Source List

    Individual Source Editor

  • 30

    Wakes Wake Length

    Wake Angle

    Component Chooser

    Wake Switch

    Mesh Output

    ‘Go’ Button

  • 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

  • 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’.

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