Flow Characteristics of a Supersonic Open Cavity

Abstract

An open cavity flow exhibits intense self-sustained oscillations. This transient behavior stimulates violent pressure fluctuations because of multiple-order cavity tones. Detached eddy simulation was conducted to simulate the cavity flow at the freestream Mach number of 1.19. In order to improve the understanding of the shear layer convection processes and frequency characteristics the velocity of the flow field at cavity mid-span was studied using the dynamic mode decomposition (DMD) algorithm. The first three modes of the supersonic cavity flow were extracted to describe the flow configuration at the dominant frequencies. The two-vortices, three-vortices, and four-vortices are the corresponding first three DMD modes. The simplified mode structures are proposed to explain the flow dynamics in a supersonic cavity. When a feedback compression wave encounters the extrusion wave at a special location, an “analogous sonic boom” phenomenon appears causing violent noise in the cavity.