STABILIZATION OF SUPERSONIC BOUNDARY LAYER IN MOLECULAR GAS BY LOCAL EXCITATION OF THE VIBRATIONAL MODE

The paper investigates the influence of local energy input on the stability of a supersonic boundary layer on a flat plate with a Mach number M = 4.5 using a two-temperature model of a single-mode vibrationally excited gas. A source with a Gaussian power profile of low variance was placed near the upper boundary of the boundary layer. The real process of pumping the vibrational mode with laser radiation was modeled, in which part of the energy is transferred directly into heat. It is shown that in all cases, most of the layer is heated, its temperature increasing monotonically with the fraction of energy directly converted into heat. Calculations of the neutral stability curves showed that with increasing temperature, the critical Reynolds numbers Re_δcr increase. In all regimes, the critical Reynolds numbers exceed the corresponding value for a perfect gas without energy input. This leads to the conclusion that the stabilizing effect of the source is achieved through heating of the upper and middle parts of the layer, leading to a decrease in the effective Reynolds number of the flow. A comparison of the critical Reynolds numbers Re_δcr and of the transition Reynolds numbers Re_δT was performed during pumping of the oscillatory mode with cooling of the wall up to the temperatures T_w = T_∞ , where T_∞ is temperature of the carrier flow. The obtained data allow us to conclude that the compared methods are quite competitive.

linear stability, local energy source, vibrational mode, critical Reynolds number, wall cooling