Methods for the Accurate Computations of Hypersonic Flows: I. AUSMPW+Scheme

In order to overcome some difficulties observed in the computation of hypersonic flows, a robust, accurate and efficient numerical scheme based on AUSM-type splitting is developed. Typical symptoms appearing in the application of AUSM-type schemes for high-speed flows, such as pressure wiggles near a wall and overshoots across a strong shock, are cured by introducing weighting functions based on pressure (AUSMPW). A newly improved version of the AUSMPW scheme, called AUSMPW+, is developed to increase the accuracy and computational efficiency of AUSMPW in capturing an oblique shock without compromising robustness. With a new definition of the numerical speed of sound at a cell interface, capturing an oblique shock is remarkably enhanced, and it can be proved that an unphysical expansion shock is completely excluded. With simple Mach number interpolation functions, AUSMPW+ is efficient to implement. Extensive numerical tests from supersonic frozen flows to hypersonic nonequilibrium flows validate that the AUSMPW+ scheme provides accurate solutions for the computation of high-speed flows.