Direct Numerical Simulation of the Transition Process in a Separated Supersonic Ramp Flow

Abstract

Despite intensive theoretical and experimental research, transition to turbulence in separated hypersonic ramp flows is still a challenge to predict. One of the most successful approaches to model the dominant mechanisms is direct numerical simulation, which has demonstrated the capability to generate reliable datasets. In the present study, different supersonic test cases are chosen from literature and compared with simulations using a high-order version of the DLR FLOWer code. The results using higher-order Pade-filter approaches are encouraging. With this validation as a background, a supersonic ramp case was chosen for study. Different ramp-angles and Reynolds numbers were investigated to determine a transitional test case, for which turbulence can be resolved behind re-attachment. A hypersonic ramp with 12° angle of attack was then chosen for three-dimensional DNS of the transition process. These DNS were carried out with different grid extents in the wall-normal direction and different sweep angles of the incoming flow with good success. Simulations of laminar-turbulent breakdown are presented using various perturbation spectra at the inflow.