Growth Characteristics of Turbulent Wakes

Abstract

Recent advances in the experimental study of hypersonic wakes at the Defence Research Establishment Valcartier have led to spatially resolved measurements of the behavior of the important physical variables which characterize the wake. Previous measurements pertained mainly to the wake growth, and they were achieved by an integrated-type technique using a schlieren system under test conditions different from those utilized at this establishment. To assist in relating the new measurements with the earlier ones, and to provide a basis for comparing growth results obtained from the spatially resolved measurements, schlieren films of model wakes taken during this program have been utilized to obtain wake growth data at the same velocities and pressures as those of the spatially resolved measurements. Both cone and sphere wakes have been investigated. Results show that the effect of P∞D (pressure times body diameter) on wake growth is negligible, while the Mach number has a strong effect. Turbulent wake growth can be described by the expression: [Formula: see text], where both the wake width Dw and the axial distance X have been normalized by the drag diameter [Formula: see text]. The factor C is a function of the Mach number M∞: C = 0.56 + 0.032 M∞.