Dynamics of Unsteady Shock Wave Reflections Using Overset Mesh Approach

The reflection of an oblique shock wave over a straight reflecting surface was investigated numerically in the classical inviscid gas-dynamics framework. A wedge in a steady supersonic flow was used to generate an oblique shock wave that was reflected from a symmetry plane. It is well known that for the steady reflection there exist only two possible configurations: the Regular Reflection (RR) and the Mach reflection (MR). The criteria of transition between them are well established for steady flows. In the present work, the leading edge of the wedge was subjected to slow/rapid rotation or periodic oscillation with different amplitudes creating unsteadiness in the flow. Such unsteadiness may cause premature RR → MR transition. However, little research has been conducted to show the effect of a continuous excitation on the dynamic development of shock wave reflections. For the rotation and oscillation of the wedge an overset framework is employed, where components are meshed individually (multiple cell zones) and typically embedded in a background mesh. The resulting multiple overlapping cell zones are connected by an overset interface. Overset grids maintain grid quality during mesh motion. The results for a flow Mach number M = 4.0 contradict the state-of-the-art knowledge regarding the RR → MR transition in steady flows, particularly for higher rates of wedge rotation. Well-conducted experimental data is often obtained in low-noise wind tunnels and numerical studies ensured disturbance-free computations to match with the experimental data. Unlike previous reports, for unsteady flows created by periodic perturbations, flow sustained a stable MR pattern well beyond its steady-state dual solution boundary.