Space-marching method on unstructured grid for supersonic flows with embedded subsonic regions

A space-marching algorithm on an unstructured grid to solve supersonic flows that may contain embedded subsonic regions is proposed. The method employs a domain-marching algorithm in which a bandlike computational subdomain is marched in the hyperbolic direction starting from the upstream boundary of the flowfield. A masking procedure is employed where the outside of the selected domain is masked during the flux computations to minimize the overall arithmetic operations. The unmasked domain is integrated in time to get a locally converged solution. If embedded subsonic regions are present, the unmasked region is enlarged to cover the entire subsonic regions surrounded by supersonic points. The method is applied to calculations of a fully supersonic flow in a scramjet and a supersonic flow with embedded subsonic regions around a blunt-nose body. It is demonstrated that the computational work can be reduced by as much as a factor of 10 as compared to conventional, time-marching unstructured grid methods.