Experimental investigation of disturbance development in the hypersonic boundary layer on a conical model

摘要

Investigations of laminar-turbulent transition at hypersonic speeds are very important because of its influence on heat transfer and drag of vehicles. Along with applied interest, these studies have a fundamental significance because they are directly related to the problem of turbulence origin. There are few experimental studies of instability of boundary layers at high Mach numbers, probably, because they are complicated and expensive. The research has been conducted for more than three decades. The latest achievements are published in [1,2]. Recently the first experiments have been performed in Germany and in Russia [3,4]. The evolution of natural disturbances has been studied in all these works, i.e., the disturbances arising in the boundary layer without any interference of the researcher. More informative is the simulation of unsteady wave processes using artificially introduced disturbances. A high frequency glow discharge is used to generate the artificial wave packets at super- and hypersonic speeds [5]. Such a packet consists of many inclined waves. The development of this wave train in the boundary layer is registered by a hot-wire anemometer. As a result, three-dimensional distributions of pulsations are obtained, which are decomposed into a Fourier series. Some results of experimental investigations of disturbance development in the hypersonic boundary layer on a 7°conical models (500mm and 166mm long) at zero angle of attack are presented in this paper. Experiments were carried out in T-326 wind tunnel of ITAM SB RAS in Novosibirsk at free stream Mach number M_∞=6 and unit Reynolds number Re_1=12.5·10~6 M~(-1). Constant temperature hot wire anemometer was used for flow pulsations measurements.