Prediction of farfield jet/trailingedge interaction noise for engine overthewing installations
Abstract
Semiempirical equations for calculating the farfield radiated noise due to the interaction of an engine jet exhaust with the trailing edge of a shielding surface have been derived. The effect of nozzle placement relative to the shield surface and the effect of airplane forward velocity are included. The analysis shows that, if the shield is shorter than the jet potential core length, the characteristic frequency of the interaction noise is independent of relative velocity and scales directly with jet velocity and inversely with the shield length. Experimental confirmation of the effect of shield length on the characteristic frequency is presented. It has also been experimentally determined that jet/trailingedge interaction noise is reduced by airplane forward velocity and scales with relative velocity to the fifth power. The scaling implied by the prediction equations confirms this result if the shield is shorter than the exhaust jet potential core length. If the shield is longer than the potential core length (which is stretched due to forward velocity), the analysis shows a dependence on the product of jet velocity squared and relative velocity cubed. No experimental data is available for this case.
 Publication:

American Institute of Aeronautics and Astronautics Conference
 Pub Date:
 July 1976
 Bibcode:
 1976aiaa.confR....F
 Keywords:

 Engine Noise;
 Far Fields;
 Jet Exhaust;
 Trailing Edges;
 Noise Spectra;
 Nozzle Geometry;
 Prediction Analysis Techniques;
 Strouhal Number;
 Acoustics