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ENH: cvMesh.org : moved to nonRelease
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doc/cvMesh.org
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doc/cvMesh.org
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# -*- mode: org; -*-
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#
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#+TITLE: cvMesh usage
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#+AUTHOR: OpenCFD Ltd.
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#+DATE: June 2011
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#+LINK: http://www.OpenFOAM.com
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#+OPTIONS: author:nil ^:{}
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#+STARTUP: hidestars
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#+STARTUP: odd
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* Method
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+ initial point seeding. These are the background points to
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- start the triangulation from (a subset)
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- do cellsize and alignment queries on
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+ mesh movement based on cell size and alignment
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+ surface conformation by introducing duplicate points
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+ do final simplification by face filtering
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* Typical work flow
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+ clean surfaces (surfaceClean, surfaceOrient)
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+ set in system/controlDict
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- startTime to latestTime
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- endTime to number of meshing iterations
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- writeInterval to large value
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+ select defaultCellSize [m]
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+ select refinement patterns based on e.g. surface
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(cellSizeControlGeometry)
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+ select autoDensity initial point seeding
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+ force output of unfiltered mesh (to save time) by specifying unobtainable
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mesh quality:
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continueFilteringOnBadInitialPolyMesh false;
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maxNonOrtho 1;
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+ check visually
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- features resolved?
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- cell size ok? Load in targetCellSize volScalarField.
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- if any surface protusions that are unacceptable
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- lower targetCellSize
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- lower maxSurfaceProtrusionCoeff (usually 0.1 of targetCellSize)
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+ restart. Repeat until surface good enough.
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+ produce final mesh
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- set initialPointsMethod to pointFile so it reuses the Delaunay vertices
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- re-enable mesh filtering
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continueFilteringOnBadInitialPolyMesh true;
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maxNonOrtho 65; //or whatever;
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* Debugging
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+ run surfaceFeatureExtract with -writeObj to dump all features
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+ set initialPointsMethod to pointFile
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+ set writeInterval to 1
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+ run e.g. topoSet to create slices
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* Annotated output
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#+BEGIN_EXAMPLE
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Create time
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Reading geometryToConformTo
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Reading cellSizeControlGeometry
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Selecting initialPointsMethod autoDensity
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Selecting relaxationModel adaptiveLinear
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Selecting faceAreaWeightModel piecewiseLinearRamp
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Conforming to feature points
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Inserted 32 feature vertices
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#+END_EXAMPLE
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In this particular case there are 8 straight corners so these can be recreated
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with a triplet each.
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#+BEGIN_EXAMPLE
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Inserting initial points
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autoDensity
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6922 points placed
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9139 locations queried
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0.7574132837 success rate
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#+END_EXAMPLE
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The initial points get created by the =autoDensity= method. It will accept only
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part (75% in this cae) of the initial points to create randomly distributed locations.
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#+BEGIN_EXAMPLE
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6922 points to insert...
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6922 points inserted
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Build coarse surface conformation
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Initial conformation
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Number of vertices 6962
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Number of surface hits 2245
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Number of edge hits 238
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#+END_EXAMPLE
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The initial points get inserted into the triangulation and it detects the number
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of surface pierces (surface hits) and the number of XXX (edge hits).
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#+BEGIN_EXAMPLE
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Stopping iterations when:
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total number of hits drops below 0.001 of initial hits (2)
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or
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maximum number of iterations (15) is reached
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#+END_EXAMPLE
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It will introduce additional duplicate vertices on either side of the surface
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pierce to conform to the geometry. This needs to repeated until the number of
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pierces is low enough.
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#+BEGIN_EXAMPLE
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Conformation iteration 0
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Number of vertices 12166
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Number of surface hits 234
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Number of edge hits 38
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..
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Conformation iteration 4
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Number of vertices 12908
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Number of surface hits 0
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Number of edge hits 0
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--- [ cpuTime 5.46 s, delta 0.8 s, "Conformation iteration 4" ] ---
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--- [ 5.46 s, mem size 114228 kB, mem peak 114228 kB, mem rss 28712 kB ] ---
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Total hits (0) less than limit (2), stopping iterations
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Storing surface conformation
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Stored 5946 vertices
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Store size and alignment
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#+END_EXAMPLE
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The vertices needed to create the conformation are stored together with the size
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and alignment.
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#+BEGIN_EXAMPLE
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Time = 1
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Relaxation = 1
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Looking up target cell alignment and size
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Determining vertex displacements
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Reinserting stored feature points
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Reinserted 32 vertices
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Inserting displaced tessellation
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4328 points to insert...
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4328 points inserted
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Reinserting stored surface conformation
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Reinserted 5946 vertices
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Total displacement = (0.03629314022 0.1324815449 -0.2774017193)
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Total distance = 159.3482907
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ExecutionTime = 8.16 s ClockTime = 8 s
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Time = 2
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Relaxation = 0.9875
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#+END_EXAMPLE
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