Experimental investigation on drag and heat flux reduction in supersonic/hypersonic flows: A survey

Drag reduction and thermal protection is very important for hypersonic vehicles, and a counterflowing jet and its combinations is one of the most promising drag and heat release reduction strategies. In the current survey, research progress on the drag and heat release reduction induced by a counterflowing jet and its combinations is summarized. Three combinatorial configurations are considered, namely the combination of the counterflowing jet and a forward-facing cavity, the combination of the counterflowing jet and an aerospike, and the combination of the counterflowing jet and energy deposition. In conclusion, some recommendations are provided, especially for jet instability protection, for the tradeoff between drag and heat release reductions, and for the critical points for the operational and geometric parameters in the flow mode transition.

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A survey of drag and heat reduction in supersonic flows by a counterflowing jet and its combinations

A blunt-nosed hypersonic missile mounted with a forward-facing cavity is a good alternative to reduce the stagnation heating rates. The effects of a forward-racing cavity on heat transfer and aerodynamic coefficients are addressed in this paper. Tests were carried out in
hypersonic shock tunnel HST2, at a hypersonic Mach number of 8 using a 41 deg apex-angle blunt cone. The aerodynamic forces on the test model with and without a forward-facing cavity at various angles of attack are measured by using an internally mountable accelerometer force balance system. Heat flux measurements have been carried out on the
test model with and without a forward-facing cavity of the entire surface at zero degree angle of attack with platinum sensors. A numerical simulation was also carried out using the computational fluid dynamics code (CFX-Ansys 5.7). An important result of this study is that the smaller cavity diameter has the highest lift-to-drag ratio, whereas the medium cavity has the highest heat flux reduction. Theshock structure around the test model has also been visualized using the Schlieren flow visualization technique. The visualized shock structure and the measured aerodynamic forces on the missile-shaped body with cavity configurations agree well with the axisymmetric numerical simulations.

Investigation of Missile-Shaped Body with Forward-Facing Cavity at Mach 8

Parametric study on the drag and heat flux reduction mechanism of forward-facing cavity on a blunt body in supersonic flows

A study of performance parameters on drag and heat flux reduction efficiency of combinational novel cavity and opposing jet concept in hypersonic flows

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, flowfield 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 smalland large-amplitude fluctuations. Agreement between experiment and computations is good for the flowfield structure and surface heating of shallow cavity flows. Sharp lips produce both a recirculation region that cools the outer surface, and severe heating just inside the cavity. Rounding the lip eliminates the recirculation region and alleviates heating inside the cavity. Experimental results show that the strong oscillations associated with deeper cavities may produce a cooling effect.

B. Yuceil

Papers

Experimental and numerical study of hypersonic forward-facing cavity flow