A SIMPLE AERODYNAMIC RULE FOR HYPERSONIC SMALL DISTURBANCE FLOWS
Technical Report,01 May 1967,31 Dec 1967
AIR FORCE FLIGHT DYNAMICS LAB WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB
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A revival of interest in perfect gas hypersonic small disturbance theory is brought about by the practical possibilities of hypersonic vehicles whose slenderness, combined with the high altitude environment, makes the frozen flow, perfect gas assumption reasonable. In many cases of experimental slender body aerodynamics the predominant effect of reacting real gases is associated not with the flow over a model but rather with nonequilibrium effects in the hypersonic nozzle of high energy wind tunnels. Primarily to eliminate problems associated with wide variations and mismatch of Mach number and additional difficulties in the accurate measurement of Mach number in high energy facilities a rule is developed for the pressure coefficient for hypersonic small disturbance flows in which neither the Mach number nor the hypersonic similarity parameter appears explicitly. The solutions which result, generalized to planar and axisymmetric flows by the tangent-wedge and tangent-cone theories, accurately approximate the inherent nonlinearities of hypersonic flow for Mtau or 1, a region where classical hypersonic similarity is most important. However, the need to invoke similarity is eliminated by the availability of practical solutions. The only requirements for correlating two different inviscid flow situations over similar bodies are that gamma be known but need not necessarily be the same and that both satisfy the usual limitations of hypersonic small disturbance theory.