Relation between shock unsteadiness and the origin of side-loads insidea thrust optimized parabolic rocket nozzle

Abstract

This paper reports the results from tests carried out on a thrust optimized parabolic (TOP) nozzle to study the influence of the unsteady characteristics of fluctuating separation and reattachment shocks towards the possible origin of lateral forces in rocket nozzle flows. The study was conducted using wall pressure measurements both in axial and circumferential directions, surface oil visualization technique and from strain gauges installed on the nozzle bending tube. Experiments reveal that the nozzle pressure ratios, at which the peaks in maximum rms values occur for separation and reattachment shocks, to coincide with the nozzle pressure ratios at which peaks in strain gauge signal are observed. This indicates that the fluctuating nature of separation and reattachment shocks as directly responsible for origin of side-loads in rocket nozzle flows.