Influence of Microjets on the Interaction Pattern of a Supersonic Jet with a Flat Barrier
N. P. Kiselev, V. I. Zapryagaev, I. N. Kavun, R. A. Styazhkin, A. A. Pivovarov
Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia
Keywords: underexpanded jet, impinging jet, microjet, barrier, self-oscillation regimes, pressure pulsations
Abstract
The characteristics of pressure pulsations on a flat semi-infinite barrier impinged by a supersonic underexpanded jet are investigated. The Mach number at the nozzle exit is M а = 1, the degree of underexpansion is n = 2,1, and the distance from the nozzle exit to the barrier is h/Dа = 2 ÷ 15 ( Dа is the nozzle exit diameter). It is shown that tangential injection of six microjets can significantly reduce pressure pulsations on the barrier. The mass flow through all microjets is 0,3 % of the mass flow through the main jet. It is established that when h/Da < 3, a self-oscillatory mass-flow regime of jet-barrier interaction occurs; when 3 < h/Da < 8, a self-oscillatory regime with acoustic feedback takes place; and when h/Da > 8, the turbulent aperiodic interaction regime is realized.
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