Prediction of the low Mach number jet noise issued from rectangular nozzle is described. Firstly measurements of the jet noise were conducted at the low Mach number flow condition. We found that the sound power of the jet obeyed 6-th power of the jet velocity. This means the jet noise is not dominated by the quadrupoles distributed in the shear flow of jet, but by the dipole distribution on the surface of the exit of the nozzle. The model of vortex sound is applied as the sound generation mechanism in numerical simulation. The sound emission from the vortices in the shear flow is modified with the compact Green's function representing the scattering effect by the surface of the exit of the nozzle in the lower frequency range. It is also modified by the non-compact Green's function in the higher frequency range. Approximated analytical functions are derived for the Compact Green's functions. Lastly calculated sound spectra are compared with measured spectra. The comparison proved effectiveness of the prediction procedure.
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