Flow separation due to jet pluming.

Abstract

D missile ascent rapidly decreasing ambient pressure causes the rocket exhaust plume diameter to equal and exceed the vehicle length. At sufficiently high altitudes, the plume interacts with the vehicle flowfield and produces a boundary-layer separation that can occur well forward of the vehicle base. Because this phenomenon significantly influences vehicle stability, heating, and stage separation, the conditions at which plume-induced flow separations can occur are naturally of interest. In a series of wind-tunnel experiments, large regions of plume-induced flow separation have been demonstrated by Falanga et al and by Vick et al using cold-flow jet simulation techniques. Since these available data indicate a considerable degree of configuration dependence, they cannot be used readily to predict flow-separation characteristics for arbitrary missile shapes. Furthermore, the adequacy of the jet simulation techniques used to simulate vehicle-plume interaction has not been demonstrated. Additional wind-tunnel tests now have been conducted in order to determine the plume-induced flow-separation pattern to be expected on several typical missile configurations. Furthermore, a flight program using one of the windtunnel configurations has served to check the validity of the jet simulation techniques. The results of these tests are reported in this note.