Tohoku University
Sendai 980, Japan
The paper consists of two main parts. The first part represents an overview of previously developed 2D and 3D adaptive unstructured Euler solvers. The solvers are based on triangular (2D) and tetrahedral (3D) boundary-fitted unstructured grids, the classical adaptive transient h-refinement/derefinement technique and a second-order non-oscillatory Godunov-type scheme. Considerable attention is given to efficient data structures developed for 2D and 3D cases, scalar and vector processing. Special procedures for vectorization and parallelization are also discussed.
Then the above adaptive codes are applied to the investigation of 2D and 3D problems dealing with regular-to-Mach reflection transition for essentially unsteady \forcenl flows. Firstly, an attempt is undertaken to get precisely the transition location for a truly unsteady flow with curved shocks and to conclude about applicability of the von Neumann theory to unsteady flows. It turns out that the current preliminary data with the grid resolution of about 6 microns (while the characteristic scale of computational domain chosen on the basis of available experimental data is about 36 cm) allowing quite interesting speculations are still not sufficient to get an ultimate conclusion. A new run with minimal grid spacing of 0.7 microns is under way now.
Secondly, initially plane shock wave reflection from an inclined circular cylinder is considered. The Regular-to-Mach reflection transition takes place on the cylinder side wall. The computations show remarkable peculiarities of the transition. In particular, it is reasonable to suggest that Mach reflection may start away from the ground wall and during some time two transition points may co-exist simultaneously on the cylinder surface.
Both the above studies lean essentially on interferometric experimental data and advanced postprocessing techniques creating experimental-like images from unstructured numerical data.