A Highly Scalable Direction-Splitting Solver on Regular Cartesian Grid to Compute Flows in Complex Geometries Described by STL Files

We implement the Direction-Splitting solver originally proposed by Keating and Minev in 2013 and allow complex geometries to be described by a triangulation defined in STL files. We develop an algorithm that computes intersections and distances between the regular Cartesian grid and the surface triangulation using a ray-tracing method. We thoroughly validate the implementation on assorted flow configurations. Finally, we illustrate the scalability of our implementation on a test case of a steady flow through 144,327 spherical obstacles randomly distributed in a tri-periodic box at Re=19.2. The grid comprises 6.8 billion cells and the computation runs on 6800 cores of a supercomputer in less than 48 h.