Description: The high-intensity level acoustic load generated by large launch vehicle lift-off propulsion is of major concern for the integrity of the launch complex and the vehicle payloads. The currently practiced computational methods are unable to offer the reliability of both the noise generation mechanism and acoustic environment. In order to uniquely address both of these critical aspects, the proposed approach will unify the physics of noise production with propagation and structural interactions. This method will utilize hybrid LES/RANS modeling established in NASA production flow solvers (Loci-Chem and OVERFLOW) capable of realistic descriptions of flow-acoustic interactions. A non-dissipative acoustic Boundary Element Method (BEM) will be coupled with the well-resolved noise source for high-quality acoustic environment predictions, equipped with the Fast Multipole Method (FMM) for solution acceleration. In Phase I, merits of the proposed approach will be investigated for plume impingement problems. A high-performance simulation architecture, easy user interfaces and post-processing utilities will be developed for complex geometries and efficient large-scale simulations. Phase II efforts will involve refinements and extensive evaluations for high-resolution noise source modeling, transition of mixed speed flow regimes, wave propagation through non-uniform flow, and supercomputing capabilities facilitating new insights into rocket exhaust acoustic loading and comprehensive noise suppression analysis.

Benefits: The proposed innovation offers significant advantages over aeroacoustic prediction tools currently available in industry. The hybrid LES/RANS and acoustic BEM modeling will provide a unique combination of high-precision multi-physics tools. The proposed approach will offer a great technology advantage through its ability of high-quality predictions and fast simulation turnout. The toolset will be invaluable to launch service providers and payload system and sensitive instrument developers, particularly for one-of-a-kind DoD, NRO, and NOAA satellites. At the end of the SBIR, this technology will be readily available for analysis of micro-jet or other active/passive control systems, conventional and vertical landing jet engine noise, and airframe noise in general.

The Computational Aero-Acoustics (CAA) tool will be of first order importance in defining lift-off environments for Shuttle and new heavy lift launch vehicle designs, and for the analysis of noise suppression techniques such as targeted placement of water deluge systems or shaping of launch platform surfaces and exhaust ports to reduce the noise sources. The developed tool will provide greater confidence to NASA acoustics engineers offering accurate, quantitative acoustic loading predictions from first principle CFD/CAA simulations for specific launch vehicle configurations. The tool will also be invaluable to payload system and instrument developers, particularly for one-of-a-kind and experimental optics and telescope systems.