EFFECT OF AZIMUTHAL MODES ON THE STABILITY OF MICROJET FLOWS OF VIBRATIONALLY NONEQUILIBRIUM SF6
I.S. Tsyryul'nikov, T.V. Poplavskaya, S.G. Mironov
Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
Keywords: supersonic underexpanded jet, vibrational relaxation, stability, laminar-turbulent transition
Abstract
A numerical study is performed on the development of disturbances in weakly underexpanded vibrationally nonequilibrium and equilibrium SF6 jets issuing from axisymmetric sonic micronozzles into an SF6 medium. The numerical simulation is based on solving unsteady three-dimensional Navier - Stokes equations using a two-temperature model of relaxing flows. Spectral analysis of the velocity disturbances in the mixing layer with respect to frequencies and azimuthal wave numbers shows that the initial disturbance level of the first asymmetric azimuthal mode determines the position of the laminar-turbulent transition. In a nonequilibrium microjet, this level is an order of magnitude lower than in an equilibrium one, which leads to a longer laminar section of the microjet.
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