Internal:IMR 2018 Short Course

Notes

• A parallel advancing front grid generation scheme, Rainald Löhner, Int. J. Numer. Meth. Engng. 2001 [1]

Summary

A parallel advancing front scheme has been developed. The domain to be gridded is first subdivided spatially using a relatively coarse octree.

Boxes are then identified and gridded in parallel. A scheme that resembles closely the advancing front technique on scalar machines is recovered by only considering
the boxes of the active front that generate small elements.

 

Grid generation

 

The algorithm uses many passes.

In each pass the faces of the front are divided using an octree. From faces in "far enough " octree leaves points are advanced simutaneusly

only the boxes covering the active front in regions where the smallest
new elements are being introduced are considered.

Shared Faces between leaves are eliminated shifting the octree leaves and remeshing the front.

Work balancing is achieved using overdecomposition of the octree.

Mesh Improvement

Swapping

Checks are done in parallel , actual flipping sequentially

Removal of bad elements (Edge Contraction)

Indentify edges around bad elements in parallel , contract them either by collapsing an endpoint onto the other or both onto a new point in the middle.

Laplacian Smoothing

Color edges/elements  into independent sets and run in parallel. When negative volume elements are created, remove them together with adjacent elements and remesh the hole.

For surface meshing (preprocessing) each surface patch is meshed in parallel.

Results

Shared memory.

Performance more than 50% efficiency in 16 cores