Wall distance search algorithm using voxelized marching spheres

Minimum distance to a solid wall is a commonly used parameter in turbulence closure formulations associated with the Reynolds Averaged form of the Navier Stokes Equations (RANS). This paper presents a new approach to e ciently compute the minimum distance between a set of points and a surface. The method is based on sphere voxelization, and uses fast integer arithmetic algorithms from the eld of computer graphics. An unstructured grid around an aircraft con guration (DLR-F6) is chosen as the test case for demonstration and validation. Multi-processor computations (up to 256 processors) are conducted to study e ciency and scalability. Encouraging results are obtained, with the sphere voxelization algorithm demonstrated to be more e cient than all of the alternate methods for computing minimum distances. However, a load imbalance does exist, which negatively impacts the scalability for large number of cores. A simple method for load re-balancing is formulated and tested, which results in signi cant improvements in both e ciency and scalability.