Calcul du spectre acoustique d'un jet libre subsonique soumis à une injection de masse

Abstract
We give a model of the acoustic radiation field of a cylindrical free jet. This model is based on Lighthill's equation with a simplified source term. The theoretical expression of the radiated acoustic field includes the coherence of acoustic sources present in the jet. That means that a normalized cross-spectral density according to a convected Gaussian form function of correlation is assumed for the source quantity. We define then the coherence parameters of this function which are introduced in the computation. As this values can't be determined from theoretical considerations, they are derived from experimental investigations. The sound power spectrum and level of a turbulent free jet in interaction with a injection wreath of cold air are then computed.