Modes of unsteadiness in shock wave and separation region interaction in hypersonic flow over a double wedge geometry

This study investigates different modes of unsteadiness that could be seen in a hypersonic flow over a double wedge configuration with a large separation region size. In the previous studies with a double wedge or a double cone configuration, small turn angles of the surfaces are seen to produce a small separation region that does not interact with the outside shock structures and produce a steady flow. However, a large separation region can be observed with large wedge angles that could interact with the outside shock waves and produce different types of unsteady flows. Some recent numerical studies on the double wedge configuration with a large fore-wedge angle (θ1) of 30° and various aft-wedge angles (θ2) at the free-stream flow Mach number (M∞) of 7 have shown that the flow exhibits periodically oscillating states. The current study investigates this geometric configuration over the parameter space of wedge length ratios (L1/L2) of 0.5, 1.0, 1.5, and 2.0 and aft-wedge angles (θ2) of 45°, 50°, 55°, and 60°. Three modes of unsteadiness are observed, namely, vibration mode, oscillation mode, and pulsation mode. The effect of the variation in geometric parameters on switching between different modes of unsteadiness is assessed, and it is shown that the unsteady characteristics of the flow are determined by the size of the separation region and location of the shock waves with respect to it.