A time domain approach for shock noise prediction with decomposition analyses of large-scale coherent turbulent structures in jets

摘要

Broadband shock-associated noise (BBSAN) is one dominant component from off-design supersonic jets. A time-domain BBSAN model is proposed and evaluated, which is based on the vector Green & rsquo;s function solution of the decomposed Navier & ndash;Stokes equations. The source term is the scalar product of the anisotropic velocities with the mean pressure gradient. The approach uses large-eddy simulation (LES) databases. Proper orthogonal decomposition (POD) is applied to the scalar source field to extract the large-scale coherent structures associated with BBSAN. The key features of the BBSAN spectra are preserved when only a small fraction of POD modes are used to reconstruct the source field. The leading POD modes of the source term show strong amplification in the observer direction. Noise source contour plots calculated with these POD modes reveal that most noise sources are distributed at the shock-turbulence interactions. Predictions are validated with the Ffowcs Williams and Hawkings method and experimental data.