Effect of gas compressibility on the stability of a boundary layer above a permeable surface at subsonic velocities

In the present study we investigate the stability of a boundary layer for the condition that the velocity perturbations at the permeable surface are nonzero. The stability for the boundary layer of an incompressible liquid in such a formulation was considered in [1]. For the case of subsonic velocities the effect of compressibility on the flow inside the boundary layer is weak, and in the present article this effect was neglected. The unsteady flow in narrow pores of a permeable covering depends strongly on the compressibility of the gas. Therefore, in the derivation of the relation connecting the pressure oscillations at the permeable surface with the oscillations of the flow through it, the effect of the compressibility was taken into consideration. It is shown that the boundary conditions, and therefore also the stability of the boundary layer at the permeable surface, depend considerably on the Mach number, even for a subsonic exterior flow.     

Excitation by sound of Tollmien-Schlichting waves in a supersonic boundary layer

The interaction of sound with a supersonic boundary layer is considered. Because of the dependence of the main flow on the longitudinal coordinate, a sound wave generates unstable oscillations within the boundary layer. Calculations made for Mach number M = 2.0 and dimensionless frequency 2πfv_e/U_e ² = 0.91·10^?4 showed that near the lower branch of the curve of neutral stability a Tollmien—Schlichting wave can be excited with an intensity 2–3 times greater than that of the external acoustic wave.     

Interaction of hydrodynamic external disturbances with the boundary layer

Disturbances produced by external flow vorticity in a supersonic boundary layer are studied. It is shown that both vortical and nonvortical waves play an important role. The calculations are performed for subsonic and supersonic flows for a Mach number M=2.     

Erratum to: “Giant Gamow-Teller Resonance in Neutron-Rich Nuclei”

Physics of Atomic Nuclei -     

Synthesis of 4-styryl-2,3-dihydro-1H-1,5-benzodiazepin-2-ones

4-Styryl-2,3-dihydro-1H-1,5-benzodiazepin-2-ones were synthesized and their structure was established by means of PMR spectra and mass spectroscopy.Dnepropetrovsk State University Named in Honor of 300th Anniversary of the Reunion of Ukraina and Russia, Dnepropetrovsk 320625. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1560–1562, November, 1987.