Large eddy simulation of compressible turbulent jets

Increasing noise regulation at urban airports force jet engine manufactures to develop and build quieter engines. Over the last 10-15 years, a signicant reduction in fan and mechanical noise has been achieved. However, the reduction in jet noise over the same time period is fairly small and a major reduction in acoustic emissions of jet engines has to come from a reduction in jet noise. Traditional jet mixing-noise predictions are based on a statistical description of the jet turbulence; space-time correlations of the Lighthill quadruples (Lighthill 1952, Lighthill 1954) are specied in the jet. Further renements are, however, needed to obtain a reasonable prediction of the directivity and spectral distribu-tion of the radiated noise (Goldstein 1976). Signicant improvements are achieved by modeling the eects of source-convection (Lighthill 1954, Ffowcs Williams & Hawkins 1969) and mean-flow refraction (Mani 1976). Reynolds-averaged mean flow calculations can be used to provide the source-strength distribution and the length and time-scale estimates needed in the source models (Bechara et al. 1994). The empirical input needed in such an approach places limits on the range of appli