Assessment of Jet Noise Analysis Codes for Multistream Axisymmetric and Forced Mixer Nozzles

Abstract

Jet noise effects produced by an axisymmetric multistream exhaust nozzle have been examined using computational and experimental techniques. The current approach for designing low noise exhaust systems uses empirical rules and computational e uid dynamics (CFD) calculations aimed at lowering peak velocities and/or temperatures. Engineers need to be able to predict noise directly and use predictions to support their specie c design goals. The computational approach utilized in this paper applies a state-ofthe-art CFD Navier ‐ Stokes analysis (NASTAR), in conjunction with a computationally based aeroacoustics analysis. The aeroacoustic analysis uses mean e ow properties and turbulent kinetic energy/ dissipation variables as input parameters for the aeroacoustic solver. Predictions have been made and compared to experimental data obtained in NASA Lewis Research Center’ s open-jet facility. More specie cally, comparisons of aerodynamic and acoustic parameters have been made for axisymmetric nozzles to identify the effects of turbulence level, compressibility, geometrical sizing, and forward e ight on measured levels of jet noise. Applicability of this analysis approach to three-dimensional forced mixer cone gurations has also been explored, with a limited degree of success.