Implicit LU Time Integration Using Domain Decomposition and Overlapping Grids

An implicit LU-SGS (Lower-Upper Symmetrie Gauss-Seidel) algorithm is used for the simulation of reactive and non-reactive three dimensional high speed flows (supersonic combustion). The numerical method is based on an all Mach number preconditioning to enable convergence of the compressible flow solver in the low Mach number limit. The code is fully vectorized and may be used on massively parallel computers using MPI. Parallelization is performed by domain decomposition which causes losses in efficiency of the implicit numerical solver. Therefore overlapping domains are introduced to reduce both losses in convergence rate as well as in robustness. A comparison with non-intersecting grids demonstrates the effectiveness of this method. To investigate both approaches a 3-D turbulent Mach 3.85 supersonic ramp flow with shock wave boundary-layer interaction is chosen. The simulations use up to 256 nodes on a Cray T3E and up to 16384 blocks for the discretization of the computational domain. In addition results for a 3-D supersonic ramp combustor are presented. The finite-rate chemistry reaction mechanism involves 20 reactions and 9 different species.