Some peculiarities of the development of disturbances in supersonic flow under the variation of mean parameters

Abstract

The influence on linear stability of the variations of dynamic and thermal boundary layers of compressible gas at the implementation of various techniques of controlling the flow regimes (the use of the external flow gradient, distributed mass exchange (blowing or suction) and heat exchange in the form of a heating or cooling of the streamlined surface) at supersonic speeds is considered. At low Mach numbers (M = 2), vortex disturbances develop in boundary layers, and at the high ones (M = 5.35), they are completed by acoustic disturbances. The factors contributing to the damping of vortex modes are the negative external gradient, suction and cooling of the streamlined surface. They are followed by a formation of thinner and more filled (with high positive gradients of mean velocities in the near-wall region) of dynamic boundary layers. On the contrary, a positive external gradient, blowing, and heating thicken these layers and destabilize vortex disturbances. Acoustic waves react to the variations of mean parameters in different ways: at an external gradient and mass exchange, they respond unidirectionally with vortex ones, and in opposite direction at heat exchange. This is due to an opposite response on forming thermal boundary layers. The work considers in detail the cases when the anomalous dependencies are realized, which are related to a competitive influence of dynamic and thermal mean parameters. The curves of neutral stability and frequency sections are presented, which give the idea of the increments of disturbances. Information patterns help understanding the possible mechanisms of the effect on flow regimes.