Transition and Turbulence in Hypersonic Wakes

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Abstract
Schlieren photographs are shown of hypersonic wakes behind cones and smooth spheres with diameters d between ⅛ in. and ½ in. for free‐stream Mach numbers M = M∞ in the range 5 < M < 20 and at pressures from 0.05 atm to atmospheric. An analysis is made of the laminar wake core, of the distance xtr to transition, and of the wake diameter dw as a function of the distance x behind the missile. For slender cones, the formula ξtr = xtr/d = K(α)M1.3(Re × 10−4)−0.5 fits the data well over the range specified, 2α being the cone vertex angle. Correlations with local Mach and Reynolds numbers are also given. For all shapes, rw = Ax1/3 approximately for x > 50d. The effective ``turbulence Reynolds number,'' defined as Ret = Δ(δw3)/CDΔξ, where δw = dw/d and ξ = x/d, is found to be about unity for all turbulent hypersonic wakes observed. However, the photographic evidence does not support the hypothesis of universal similarity in turbulent hypersonic wakes. Qualitative discussions are given of observed bifilar and ablation wakes.