CSAR Titan IV Remeshing

Orion Lawlor, 2004/9/15

We began with a Gen2.5 Rocflu (fluids) dataset of the Titan IV rocket core, partitioned for 480 processors. Bob Fiedler performed the run and provided an output dump at 32ms of simulated time (available on Turing at /csar/rfiedler/GEN2.5/Titanflu/HDFout_32ms.tar.gz).

The mesh is large:

800K vertices
3.93 million tetrahedra
800MB of volume solution data (including ghosts)
Partitioned for 480 processors

We ran our remeshing and solution transfer tool "Rocrem" (checked in under CSAR CVS as Rocstar/Rocrem) on this dataset on Turing, CSAR's linux cluster. The command line used was:
./charmrun ./remesh.x -v -s Rocflu 8.32 +vp480 +p32
The remeshing process took about 20 minutes, mostly in the TetMesh and solution transfer phases.

Remeshing Results

Rocrem currently performs remeshing using the surface remeshing tool YAMS and the tetrahedral remeshing tool TetMesh. These are Simulog's commercial versions of the popular INRIA meshing tools. Because these are serial tools, we must first reassemble the surface mesh (using the FEM framework) before calling YAMS and TetMesh, then partition the resulting mesh (again using the FEM framework).

First we examine the mesh near the star grain:

Original mesh, created by Gridgen

Remeshed mesh, created by YAMS/TetMesh

And near the nozzle:

Original mesh

Remeshed mesh

In detail, the original and remeshed mesh are completely different. However, overall, the original and remeshed mesh are quite similar, because very little burning has happened yet.

Solution Transfer Results

Reconstructed boundary condition patches: purple is the burning surface; red is non-burning.

Transferred solution data: fluids pressure.

Original solution data: fluids pressure, with cutting plane.

Transferred solution data: fluids pressure, with cutting plane.

Note that the minimum value is slightly larger in the original mesh. This slight blurring of the extreme values is common, especially when there is a sharp change, such as the near-discontinuity in the exit transient.

Orion Sky Lawlor