ИСТИНА

Installation of aeroengines near aircraft's wing can give rise to an effective additional sound source associated with the interaction of the jet and the wing, which for low frequencies cannot be accounted for jet noise diffraction on the wing trailing edge. It is experimental observation that the intensity of such aeroacoustic interaction increases exponentially with approaching the jet to the wing. This effect can be explained by the fact that the hydrodynamic pulsations of the jet near field are scattered by the wing trailing edge into acoustic waves. To clarify this mechanism, a two-dimensional model problem is considered, in which an acoustic plane wave is scattered by two rigid semi-infinite plates with offset edges, the upper plate is simulating the wing while the lower plate is simulating the nozzle wall. The problem is reduced to a matrix Wiener- Hopf equation. Factorization of the kernel matrix is performed by the combination of Padé approximation and pole removal techniques. The solution obtained has shown that the approach of the wing to the mixing layer, so that the wing trailing edge protrudes into the region of instability wave dominance, gives rise to sound waves with intensity proportional to that of the instability wave near the trailing edge. The latter fact explains exponential dependence of the scattered acoustic field on the distance between the jet and the wing. Thus, the results of the present work demonstrate that the scattering of non-radiative, in the absence of the wing edge, hydrodynamic perturbations, can play significant role in the jet noise intensification in the installed configuration.