Modeling of the acoustical field due to a jet engine with ground effect

The principal noise source for a jet engine is associated with the jet exhaust. The acoustical field that is generated by a jet engine before the take-off is considered. The turbulent jet and the mixing of the hot exhaust gas with the cold surrounding air forms an acoustical source. The compressible Navier-Stokes equations describe both flow field as well as sound generation. The acoustic theory uses the hypothesis that a part of the flow field (which is the source of the acoustic field) is distinct from the properties of the ambient flow field. Thus, the velocity vector, the pressure and the density are split into semi-compressible components and inviscid, irrotational acoustical components. The turbulent flow and mixing are computed by using Large Eddy Simulation (LES). The instantaneous LES provide the acoustical source for the Lighthill's wave equation, which is used to compute the acoustical field. The computed acoustical field agrees quite well with published experimental data.