Abstract:

ESDU 88023 introduces a computer program for the prediction of the natural shielding effect of two parallel identical jets. The shielding levels are predicted in one-third octave frequency bands over a range specified by the user for an observer in the far-field at any distance and angle to the jets except in the 40 degree quadrant centred on the downstream axis of the jet. The method takes account of the velocity and temperature of the jets, their diameters and the ratio of jet density to ambient. It considers each jet in turn as a point noise source and the other as the shielding jet and superimposes the sound fields so obtained. The theory is outlined and comparison of predictions obtained with experimental results is made that shows a root mean square error between measurements and predictions of less than 0.5 dB. The method of providing the input data and the format of the output is illustrated with a worked example. The program is provided in two forms as ESDUpac A8823 and as VIEWpac M8823.