Contribution of jet flow noise sources to the far-field sound power

Abstract

Jet noise is the dominant source of noise during aircraft takeoff. This study uses direct numerical simulation (DNS) data of subsonic jet flow obtained from computational fluid dynamics (CFD) simulations to perform acoustic analyses. The non-negative contribution technique (NNC) is employed to identify aeroacoustic sources of jet noise with the greatest contribution to far-field sound power. The NNC technique uses the Lighthill source distribution with an acoustic impedance matrix constructed from radiation kernels of the free-field Green’s function. The fast multipole method (FMM) is integrated with the NNC technique to reduce computational cost arising from decomposition of the acoustic impedance matrix as well as from the high number of CFD grids associated with the DNS data. The results showed that the dominant aeroacoustic sources are associated with the first component of the Lighthill tensor (T11) and are concentrated along the jet centerline, downstream of the nozzle exit.