Experimental and numerical study of hypersonic forward-facing cavity flow

Hypersonic flow over the nose of a blunt body with a forward-facing cavity is studied both experimentally (Mach 5 blowdown tunnel) and numerically (commercial finite volume code). Trends are established for the pressure oscillations within the cavity, flow-field structure, and surface heating for different cavity depths and lip radii. Resonant pressure oscillations within the cavity are an experimental flow feature but occur numerically, for the cavity geometries studied, only if freestream fluctuations are present. The oscillations are dominated by the quarter-wave frequency of the cavity. In the numerical simulations, the oscillation strength increases with cavity depth. In the experiments, oscillation strength generally increases with cavity depth; however, for a specific midrange of cavity depths, experiments show that the pressure oscillations switch randomly between two modes of behavior involving small- and large-amplitude fluctuations. Agreement between experiment and computations is good for the flow-field structure and surface heating of shallow cavity flows. Experimental results show that the strong oscillations associated with deeper cavities may produce a cooling effect. (Author)