NACA-RM-L53H21

Abstract

INTRODUCTION <br>Considerable interest is shown currently in the aerodynamic characteristics of bodies of revolution at supersonic speeds and special attention is shown to the Reynolds number for transition and to the effects of Reynolds number upon the skin-friction drag, In references 1 and2 results are presented of an investigation of the friction drag and boundary-layer transition on cone-cylinder bodies over a range of Mach number. In this investigation, variations in Reynolds number were made by lengthening the cylindrical portion of the bodies. Reference 3 to 6 have also presented a considerable amount of aerodynamic data on a series bodies. In these tests, variations in Reynolds number were accomplished by changes in tunnel stagnation pressure. These investigations illustrate two techniques for obtaining the effect of Reynolds number upon skin friction. <br>In reference 3 data are presented which indicate a dependence of the Reynolds number for transition upon stagnation pressure. It was suggested that changes in tunnel turbulence level were responsible for this effect. <br>Additional data for bodies of revolution indicating this same phenomenon have been published in references 2 and 6 with results for several hollow cylinders presented in reference 7. Although the temperature was held nearly constant for the wind-tunnel tests, it was not clear that similar results could not have been obtained by variations in temperature, in which case the results would be more properly expressed as a function of Reynolds number per unit length. The need for further research on this phenomenon is apparent. <br>The purpose of the present investigation was to determine the effects of Mach number and stagnation pressure upon the Reynolds number for transition, and to obtain the Zero-lift skin-friction drag from measurements of total drag, base drag, and forebody pressure drag for a series of eight cone-cylinder models of varying fineness ratio. Some objections have been raised about the use of cone-cylinder bodies for skin-friction investigations because of the severe adverse pressure gradient and the possibility of local separation at the juncture of the cone and the cylinder. These objections are based on the belief that this local separation or the adverse pressure gradient or both would make the results of questionable value in assessing theoretical predictions. Although there is some justification for objections on this basis, there is also sufficient reason to investigate these bodies in that they are employed in several current and proposed missiles and have the advantage of simplified construction. <br>The tests were conducted at Mach number of 1.62, 1.93, and 2.41 over a Reynolds number range from about 0.3 X 10⁶ to 10 X 10⁶ for the condition of zero heat transfer.