To predict harmful acoustic loading due to the intense acoustic waves generated by exhaust jets from propulsion systems of launch vehicles during lift-off, a numerical method based on computational fluid dynamics is developed. High-fidelity large-eddy simulations, or hybrid large-eddy and Reynolds-averaged Navier-Stokes simulations are employed for the computation of the hydrodynamic field. Computational aeroacoustic simulations based on full-Euler equations are applied to compute acoustic propagation to the farfield. Validation and verification studies are conducted using experimental results of free and impinging jets from a 2.4%-scale solid motor. It is found that the prediction accuracy with approximately 4 dB in overall sound-pressure level is obtained for both the free and impinging jets.

Aero-vibro acoustic simulation for the prediction of harmful acoustic loading at lift-off of launch vehicle is developed. In this simulation technique, high-fidelity large-eddy simulation with computational aeroacoutics based on full-Euler equations is employed for computing jet aeroacoustics and their propagation to the outside of payload fairing. Acoustic field inside the payload fairing is computed by the coupled vibro-acoustic simulation based on finite element method. A simplified fairing model is used for the validation of the present method. An impact hammer test and acoustic vibration test using a loudspeaker in an anechoic chamber are conducted for validating the structural model. Then, the accuracy of this method is validated by using the acoustic vibration test result with a subscale rocket engine.

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