Investigation of single and twin jet interactions with plates with cut-outs

Abstract

The design and testing of the launch vehicle structure and its subsystems to withstand the lift-off acoustic loads is quite a daunting task in itself. Any effort to minimize these loads can prove to be highly beneficial as it directly influences the design, weight, and qualification of the launch vehicle components and hence the overall vehicle operating cost and time. The components of launch pad such as the launch platform and jet blast deflector are known to be the principal noise sources of the intense acoustic loads generated during lift-off. They contribute to the overall noise levels experienced by the launch vehicle by either reflecting the noise generated by the jet exhaust or by creating additional sources of noise. Earlier studies showed that the presence of cut-outs in the launch platform significantly affects the overall acoustic loads experienced by the launch vehicle. The present paper attempts to characterize the influence of cut-outs in the launch platform on the noise levels experienced by the launch vehicle, by investigating single and twin jets impinging on flat plates with and without cut-outs at varying lift-off distances. The results from acoustic measurements carried out in the near and far-field of scaled down single and twin jet launch vehicle models are discussed. The paper also attempts to relate changes in acoustic field, brought about by the different platform configurations, to the changes in flow field through flow visualization using the schlieren technique.