Asymmetric Flow Separation in de Laval Nozzle
Operation conditions of rocket engines at sea-level and at high altitudes are different. The considerable difference in value of pressure of ambient air leads to different regimes of outflow from the nozzle - from the overexpanded regime at ground level to the underexpanded at high altitude. Different regimes of outflow from the nozzle cause considerable changes in flow pattern behind the nozzle outlet cross-section. One of the problems is the presence of shock structure in outgoing jet that causes flow separation from the wall of nozzle. It is known that separation point has no stable position on the nozzle surface, but fluctuates during the time. Boundary layer separation leads to the development of an asymmetric developed unsteady flow separation, and hence to unstable in time side-loads on the nozzle. Although modern rocket nozzles have a high longitudinal strength, they are not designed for side loads of high magnitude. The problem of high side loads was encountered in engine testing Vulcan rocket Ariane-5 [1, 2, 3]. Studies have shown that at the expiration of overexpanded regime two patterns of the jet of a nozzle implement, so-called free (Free Shock Separation, FSS) and restricted (Restricted Shock Separation, RSS) separation, with the side loads appearing in both cases .
KeywordsParticle Image Velocimetry Pressure Ratio Rocket Engine Laval Nozzle Side Load
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