Empirical modelling of noise from high aspect ratio rectangular jets

Noise measurements have been performed on rectangular jets of aspect ratios ranging from 49 to 987 with the aim of determining the appropriate velocity and length scaling to be used in an empirical noise prediction model. The results have shown that the velocity exponent is a function of the nozzle aspect ratio, decreasing with increasing nozzle aspect ratio. In an effort to establish a general prediction model, the velocity exponent of 7 was chosen as the best compromise to represent all the measured data. The analysis of the noise measurements from high aspect ratio nozzles of varying jet height and width has shown that, for the range of aspect ratios considered, the jet sound power level scales with the nozzle height to the power of 3 and the nozzle width to the power of 1. The derived jet noise scaling has been validated with independent experimental data and shows good agreement.