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A M odular D esign for a P arallel M ultifrontal M esh G enerator. J.P. Boufflet, P. Breitkopf, C. Longeau, A. Rassineux, P. Villon. Université de Technologie de Compiègne. UMR CNRS 6599 HeuDiaSyC (department of computer science) - PowerPoint PPT Presentation
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UMR CNRS 6599 HeuDiaSyC, UMR CNRS 6066 Roberval
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A Modular Design for a Parallel Multifrontal
Mesh Generator
J.P. Boufflet, P. Breitkopf, C. Longeau, A. Rassineux, P. Villon
Université de Technologie de Compiègne
UMR CNRS 6599 HeuDiaSyC (department of computer science)UMR CNRS 6066 Roberval (department of computational mechanics)
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Parallel volume mesh generator:
• parallelize a mesh generation code
• decompose the data
Re-use of an existing sequential volume mesh generator
Two strategies are possible:
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The sequential volume mesh generator used
•the initial data: a triangular surface mesh•needs a closed envelope•generates the internal tetrahedrons •less initial data than generated data
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Splitting of a closed envelope (1)
•based on a Moving Least Square technique•updating the cutting plane
position and direction•by using an attenuation function only the points « close enough » to the
current cutting plane are taken into account•balance the number of surface node
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Splitting of a closed envelope (2)
We obtain a cutting plane splitting the initial triangular surface mesh into two parts havingroughly the same number of nodes
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geometric decomposition
Triangular surface mesh(the domain envelope)
Module 1
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Interface mesh generation (1)
•define the interface surface nodes close to •with this boundary area define a border line C•project the surface nodes of C to •generate a surface mesh using this geometry with a standard 2D mesh generator•fit this new surface mesh to initials coordinates of the interface surface nodes
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Interface mesh generation (2)define the interface surface nodes close to
(1)
We obtain two open subdomains and a boundary area near the cutting plane
S1 the triangular finite elements on one side of
S2 the triangular finite elements on the other side of
S3 the triangular finite elements near
distance criterion the boundary area
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Interface mesh generation (3)define the interface surface nodes close to
(2)
We assign the triangular finite elements of the boundary area
“crown”
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Interface mesh generation (4)define the interface surface nodes close to
(3)
That defines a border line C composed of interface surface nodes splitting the initial triangular surface mesh into two open subdomains
C
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Interface mesh generation (4)•project the surface nodes of C to •generate a surface mesh using this geometry with a standard 2D mesh generator
We obtain a new plane surface mesh
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Interface mesh generation (5)fit this new surface mesh to the initial
coordinates of the interface surface nodes
Merge this new surface mesh with the two open subdomains
By restoring the initial coordinates of the surface nodes of C
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Interface mesh generation (6)
We obtain two new triangular surface meshescorresponding to two closed envelopes compatiblewith the sequential volume mesh generator used
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geometric decomposition
interface mesh generator
Triangular surface mesh(the domain envelope)
Module 2
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Sequential volume mesh generator
We apply the sequential volumemesh generator on each closed envelope of each subdomain
We obtain two volume meshes
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geometric decomposition
interface mesh generator
sequential volume mesh generator
Triangular surface mesh(the domain envelope)
Module 3
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Volume mesh merging
The interface surface mesh is the same
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geometric decomposition
3D volume mesh
interface mesh generator
sequential volume mesh generator
volume mesh merging
Triangular surface mesh(the domain envelope)
Module 4
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geometric decomposition
3D volume mesh
interface mesh generator
sequential volume mesh generator
volume mesh merging
scheduler
Triangular surface mesh(the domain envelope)
n=2 h
Module 5
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Complex geometry
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Complex geometry
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Complex geometry
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More complex geometry
•Multiple contour•Contour with hole inside
•we know where is the material•detection of the connected components•re-assigning strategy for small parts
(intersection with
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re-assigning strategy for small parts
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Two examples of interface mesh generatedwith two different
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geometric decomposition
3D volume mesh
interface mesh generator
sequential volume mesh generator
volume mesh merging
scheduler
Triangular surface mesh(the domain envelope)
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Conclusion• the preliminary results have to be confirmed on other benchmarks• the results have to be compared with the meshes computed with the sequential volume mesh generator alone • several issues have to be addressed :
• piloting strategy for the cutting plane according to the attenuation function and the shape of the initial surface mesh• the behavior of each module has to be studied
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Future works
• design of the scheduler• coupling the parallel volume mesh generation with a solver
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Questions ?
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Clue (1.0) piloting strategy for the cutting plane according to the
attenuation function and the shape of the initial surface mesh
X the first center of gravity
the first cutting plane
material Two boundary areas the first normal vector
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Clue (1.1)
We compute the weight: wi=wref(distance(h(Xi),X)/r)
Where : • h(Xi) is the projection of surface nodeXi to the normal of
• r is a radius (area of influence)• wref(d) is an attenuation function where :
wref(d) = 0.5 (1+cos(d)) if d [0,1] and 0 otherwise
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Clue (1.2)
• detect the two boundary area• for each, compute a new center of gravity• for each boundary area, adjust a new quantity r according to each local geometry• run the partitioning algorithm on each part
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Clue (1.3)
X1
X2r1 r2
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Clue (1.4)
X1
X2
r1
r2