固体ロケットモータのフリージェットに関する経験的音響環境予測について

摘要

Acoustic field in static-firing tests of a solid motor is analyzed using an empirical method, NASA SP-8072, and numerical simulation. It is revealed from the numerical study that the Mach wave radiated from the fluctuating jet shear-layer is a dominant noise source. The numerical simulation reasonably predicts the SPLs at all measured points within the accuracy of 4 dB in OASPL. On the other hand, the empirical method overestimates the far-field SPLs located close to the jet axis by more than 10 dB. By comparing with the measured data and numerical results, the potential-core length model and the directivity model are quantitatively evaluated. It is confirmed from the results that the discrepancy originates in the directivity model and the model has a considerable impact on the prediction accuracy.