DNS of hypersonic flow over porous surfaces with a hybrid method

A numerical study is presented which investigates, through direct numerical simulation (DNS) of the Navier-Stokes equations, the characteristics of supersonic/hypersonic boundary layers over porous surfaces. Two different configurations are considered, namely a Mach 6 flow over a flat plate with periodic porosity in both the streamwise and spanwise directions, and a shock-boundary-layer-interaction (SBLI) case at Mach 2 with a localized porosity layer. The method used to carry out the numerical simulations consists of a 6th-order hybrid weighted-essentially-non-oscillatory/central-differencing (WENO-CD) scheme, which provides high numerical stability in the regions of strong gradients, while minimizing the numerical dissipation in smooth regions. A validation of the numerical code, by comparison with other high-order non-hybrid DNS codes is presented for both the configurations, as well as a grid convergence study. The effects of Reynolds number and wall cooling on the flow characteristics in the pore region and on the acoustic waves radiated by the pores are analyzed for the periodic porosity case. The role of a porosity region localized at two different streamwise positions along the flat plate on the bubble length, the mean flow features and the wall pressure is investigated for the SBLI configuration, and compared to the case of smooth wall. The results show the capabilities of the high-order finite-volume-based Cartesian-grid hybrid method in carrying out high-resolution simulations with relatively low computational cost, thus demonstrating its effciency andversatility for the DNS of multiscale hypersonic flow configurations over porous surfaces