Experimental Study of Wakes Produced by Hypersonic Cones in Free Flight

Abstract

This paper describes an experimental study of the wakes produced by hypersonic cones flying at a velocity of 15 000 ft/s in Range 3 at the Defence Research Establishment Valcartier (DREV). Three basic cone shapes have been flown: 0.7 in. base diameter, 20° included angle cones with sharp and blunted noses, and a 1.0 in. base diameter, 44° included angle sharp nose cone. Because of the complexity of the flow field generated by these cones usually flying at some angle of attack, the experimental study was limited to one set of ambient conditions, namely, a cone velocity of 15 000 ft/s and an ambient pressure of 100 Torr of air.The measurement of the wake velocity distribution by means of the sequential spark technique constituted the backbone of the experimental program on cone wakes. The technique is based on the formation of an ionized luminous path in the wake by a first spark and on the periodic reillumination of the displaced ionized path by successive sparks. Over 100 profiles of velocity were measured behind the cone shapes. Additional diagnostic tools for this study included the photoattitude and velocity measurement system of the range which was used to determine the flight history and to measure the drag coefficient of the models and also the schlieren technique which was used to measure wake growth and deflection. A wealth of original data has been obtained on the behavior of the wake generated by the three different conical models. The measurements have revealed the presence of an asymmetry in the transverse profile of axial velocity and the presence of a lateral velocity component in the wake of high lift to drag ratio cones flying at angle of attack. The variation of the wake axis and wake front velocity with axial distance has been derived and shows good agreement with other theoretical and experimental results. Due to the presence of angles of attack of different amplitude and orientation, it was not possible to determine the transverse distribution of the mean axial velocity. Nevertheless, these results should contribute to a better understanding and also to an accurate modeling of the wake of cones.