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Mass Injection in a Hypersonic Cavity Flow

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Technical Report

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The present report describes an experimental investigation of a hypersonic cavity flow with mass-injection into the separated-flow region. The experiments were carried out in a helium wind-tunnel at a free-stream Mach number of eleven. The injected gas was helium. Two parameters were varied during the study -- the mass injection rate and the height of the separation shoulder relative to the reattachment shoulder. The effects of these parameters on the distributions of pressure and heat transfer rate were investigated. Mass injection appeared to have no drastic effect on transition Reynolds number, and the cavity flow is believed to have been laminar throughout the present investigation. The effect on the cavity floor pressure of raising the separation shoulder relative to the reattachment shoulder was of the same order as the effect of mass injection, the two effects being virtually independent of one another. However, the flow in the immediate vicinity of the reattachment shoulder and downstream was primarily controlled by mass injection rate. Small amounts of mass injection were capable of completely removing the pressure peak at reattachment, and could produce a flow with almost constant pressure within and downstream of the cavity. Mass injection had a pronounced effect on the heat transfer rate in the vicinity of reattachment, and reductions of as much as a factor of six were obtained in the heat transfer peak in this region. Furthermore, the heat transfer rates up to about one cavity length downstream of the reattachment shoulder were reduced by as much as a factor of three by mass injection within the cavity.

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