Characteristics of Weakly Nonlinear Interaction of the Instability Waves in a Supersonic Boundary Layer

The results of an experimental study of weakly nonlinear interaction mechanisms of the instability waves in a supersonic boundary layer on flat plate at Mach number М = 2 are presented in the paper. The downstream evolution of artificial disturbances of small amplitude was studied experimentally. The wave characteristics of traveling disturbances were determined. Obtained, that disturbances evolution at basic frequency was happen in according to the linear theory of hydrodynamical stability. Confirmed, that subharmonical resonance on asymmetrical wave triplet was the reason of amplification of the high inclined subharmonic pulsations. The role of high-frequency disturbances was not significant in the region of weakly nonlinear interactions. The initial stage of a parametrical resonance was characterized by appearance of a stationary wave, jumps of a phase on 180° on frequency of a subharmonic in a cross-section direction, and also not symmetry in amplitude β-spectra.

Asymmetrical Ejection of Matter in a Thermonuclear Model of a Supernova Explosion

With the recent Supernova 1987a in the LMC, new and interesting possibilities have arisen for the solution of a problem relating to the explosion mechanism of supernovae. The presupernova was probably a B3Ia, the blue supergiant, and not a red giant as it was earlier thought likely. Calculations of the evolution, which have been made recently, show that the loss of hydrodynamical stability may be connected with carbon burning in the stellar core during the blue giant stage. This loss of stability of the CO core is the main factor in our explanation of the recent event of SN 1987a.Before we consider the thermonuclear model of a supernova based on a thermal flash in the degenerate CO core, let us dwell on the present situation in the theory of supernovae. The main problem in supernova theory is the simultaneity of births of a compact remnant and an expelled envelope. The compact remnant later becomes a neutron star. The expelled envelope determines the curve of brightness. Now, it is clear that a supernova explosion may result in either the total disruption of a star or in the simultaneous production of a compact remnant and an expelled envelope.