VSP File Types & VSP Meshingopenvsp.org/wiki/lib/exe/fetch.php?media=workshopv... · – Untrimmed...
Transcript of VSP File Types & VSP Meshingopenvsp.org/wiki/lib/exe/fetch.php?media=workshopv... · – Untrimmed...
Rob McDonald – Cal Poly
VSP Workshop August 21 & 22, 2014
VSP File Types & VSP Meshing
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VSP v2 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) – Design file (des, XDDM)
http://www.openvsp.org/wiki/doku.php?id=representations
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VSP v3 Input Representations • Input
– Parametric geometry (vsp) (vsp3) Incompatible change – Background image (jpg) – Surface textures (tga, jpg) – Automation script (txt) (as) Incompatible change – Airfoil definition (af) (dat) VSP, Selig, Lednicer formats – Fuselage section definition (fxs) – Cabin definition (cab) Removed – Wireframe as mesh (hrm) – Wireframe as surfaces (hrm) Removed – Triangulated mesh (stl, NASCART) (tri) Added Cart3D – Vorlax case file (cas) Removed – Design file (des, XDDM)
http://www.openvsp.org/wiki/doku.php?id=representations
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VSP v2 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) – Design file (des, 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
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VSP v3 Output Representations • Output
– Parametric geometry (vsp) (vsp3) Incompatible change – Screen capture (jpg) – Automation script (txt) Removed – Wetted area/volume report (txt, csv) – Drag buildup report (tsv) – Area ruling report (txt) (txt) Added planar slice – Mass properties report (txt) – Wireframe (hrm) – X3D 3D Web model (x3d) – Felisa (fel) Removed – Untrimmed surfaces (3dm) (stp) Replaced with STEP – Design file (des, 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 Removed
(stl, NASTRAN, Calculix) – Vorlax case file (cas) Removed – Vorlax geometry & input (inp) (csv, m) Added Degen Geom
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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
Smooth Bezier
Surface
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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
Smooth Bezier
Surface
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Quadrilateral Wireframe
Unintersected Triangle
Wireframe
Triangle Mesh
Intersected Triangle
Wireframe
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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
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Export Unintersected (before) 1
2
5
4
3
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Export Unintersected (after)
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Execute CompGeom (before) 1
2
3
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Execute CompGeom (after)
1
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Export CompGeom 1
2
5
4
3
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Practice Session • Unintersected
• CompGeom – Save for Cart3D tutorial
• Resolution Effects (quads to triangles directly) – Num Pts – Num XSecs
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CFD Mesh Generator
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CFD Mesh • Surface mesh generator
– Isotropic triangles (no stretching) – Smooth Bezier surfaces – Bezier intersection curves – Sourcing control – Curvature control – Optional wakes – Optional half-models – Optional domain modeling
• Preferred for most CFD tools – CBAero – Pointwise – AFLR3 – Fun3D – FlightStream – TetGen
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Local Radius of Curvature
Greatest Principal Normal Curvature r = 1k
r
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Curvature Meshing Criteria
l =N > 2; r ⋅2 ⋅sin π
N( )N ≤ 2; r ⋅ 4 N
#
$%
&%
l = r > g; 2 2 ⋅ r ⋅ g− g2
r ≤ g; 2 ⋅ g
$%&
'&
g
l
l
Num CircleSegments = 8
Max Gap Num Circle Segments
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Growth Ratio Limiter
0 2 4 6 8 10
1
1.2
1.4
1.6
1.8
2
X
Gro
wth
Rat
io
Limits length of next edge to ratio of current edge.
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Rigorous 3D Growth Limiting
Off (faster)
On (slower)
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Source Types Point Line Box
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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
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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
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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
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‘Top’ Model
File on the wiki.
Constant curvature (constant radius)
Increasing curvature (decreasing radius)
Extreme curvature (vanishing radius)
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CFD Mesh GUI
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Global
Global Source Adjustment
Global & Curvature Meshing Criteria
Intersect Subsurfaces
Choose Set
Mesh Output
‘Go’ Button
Rigorous Limiting Switch
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Display
Display Switches
Mesh Output
‘Go’ Button
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Output File Output Switches
Mesh Output
‘Go’ Button
File Paths
File Browser Button
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Sources Component Chooser
Select Surface
Source Type Chooser
Add/Delete Buttons
Mesh Output
‘Go’ Button
Component Source List
Individual Source Editor
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Domain Half Mesh Switch
Far Field Switch
Far Field Mesh Size
Far Field Comp/Box Switch
Mesh Output
‘Go’ Button
Far Field Component List
Far Field Box Controls
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Domain Modeling
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Wakes Wake Length
Wake Angle
Component Chooser
Wake Switch
Mesh Output
‘Go’ Button
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Practice Session • CFD Mesh
– ‘Top’ model – Experiment with meshing parameters – Turn all criteria off – ‘play’ with one at a time – Follow meshing strategy
• CFD Mesh – ‘Your’ model – Follow meshing strategy
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Command Line / API Coming Soon!