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Effort has recently been devoted to finding a means to alleviate the effects of the reflection at the walls of the range tank of the bow and wake shock system originating with a hypersonic projectile. (Author)

A comprehensive experimental program has been conducted in the ballistics range facilities of the U. S. Naval Ordnance Laboratory to determine various aerodynamic characteristics of wakes behind hypervelocity bodies. The effects of Mach number, Reynolds number, and wall-to-stagnation enthalpy ratio on base flow geometry and transition from laminar to turbulent wake flow were investigated. It was found that the wake transition characteristics can be described in terms of two wake transition Reynolds numbers. The transition Reynolds numbers increase with both increasing flight Mach numbers and increasing wallto-stagnation enthalpy ratios. In a certain Reynolds number region the transition Reynolds numbers are independent of the body Reynolds number. The growth of laminar and turbulent wake behind cones of various half-angles and spheres was investigated. It was found that the higher the pressure drag coefficient, the steeper the growth of the turbulent near wake. The behavior of the edge of the turbulent wake was studied and described in terms of statistical parameters. It was found that the edge roughness increases at the same rate as the average wake width, and the small-scale structure of the hypersonic turbulent boundary layer persists for some distance in the near wake.

References 1 Wilson, L. N., "Body shape effects on axisymmetric wakes: transition," AIAA J. 4, 1741-1747 (1966). 2 Clay, W. G., Labitt, M., and Slattery, R. E., "Measured transition from laminar to turbulent flow and subsequent growth of turbulent wakes," AIAA J. 3, 837-841 (1965). 3 Lees, L., "Hypersonic wakes and trails," AIAA J. 2, 417428 (1964). 4 Wilson, L. N., "Far wake behavior of hypersonic spheres," General Motors Defense Research Labs. TR 66-19 (1966); also AIAA J. (to be published). 5 Behrens, W., "Flow field and stability of the far wake behind cylinders at hypersonic speeds," PhD Dissertation, California Institute of Technology (1966). 6 Webb, L., Hromas, L., and Lees, L., "Hypersonic wake transition," AIAA J. 1, 719-721 (1963). 7 Hromas, L. and Lees, L., "Effect of nose bluntness on the turbulent hypersonic wake," Ballistics Systems Div. TDR-62354 (1962).