Unsteady Nature of Flow Separation Inside a Thrust Optimized Parabolic Nozzle

Kurzfassung

An experimental investigation was carried out to study the unsteady nature of flow phenomenon in thrust optimized parabolic rocket nozzles as a function of nozzle pressure ratio especially during the transition phase during which the separation shock jumps downstream at a certain nozzle pressure ratio. The study was conducted using wall pressure measurements both in axial and circumferential directions, color Schlieren images of exhaust plume and surface oil visualization technique. The experiments reveal the jump in separation front during the transition phase to be asymmetric (for the first time) that is accompanied by violent fluctuations of the separation shock. Such an unsteady asymmetric transition process seems to be the prime cause of considerably high side-loads observed earlier rather than just the downstream jump in separation front.