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Estimation of Unsteady Pressure Field for Space Vehicle

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Our customer is a subsidiary of a multi-national aerospace and defense corporation that provides civil and military space systems and services. They are the prime contractor for an expendable launch vehicle that is used to deliver payloads into geostationary orbits. They were interested in estimating unsteady the pressure field exerted on the external surface of the launch vehicle during its ascent for direct use in vibro-acoustic analysis. A numerical simulation tool to predict the unsteady field in the frequency range of 5 Hz to 1000 Hz was thus desired.

Zeus Numerix employed coupled CFD-CAA methodology for calculating noise sources generated by flow entrainment of rocket exhaust jets. Unsteady compressible flow field using URANS (Unsteady Reynolds Averaged Navier Stokes) was simulated using Zeus\' own proprietary CFD tools. Noise sources were classified along the jet boundary as mono-poles, dipoles and quadruples. Lastly, an FW-H (Ffowcs-Williams Hawkings) acoustic solver was developed to calculate noise at target points.

Illustration
Control surface enclosing the zone of turbulence in rocket jet

The customer was delivered with the detailed numerical analysis report containing data for sound pressure level (dB) at different frequencies, noise propagation around the jet and acoustic load on fairings. It was concluded that mesh sizes greater than 15 million cells were a must for reasonable prediction. Higher mesh refinements and LES turbulence model will be needed to simulate for frequencies greater than 200 Hz.

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