Installation Effects on the Flow and Noise of Wing Mounted Jets

摘要

It is known experimentally that a jet mounted under a wing generates more noise than the same jet in isolation. The excess noise is referred to as installation noise. Installation noise is largely of aerodynamic origin. The principal mechanism is believed to be the impact of the downwash of the wing flap on the jet flow. The downwash causes the jet to deflect downward and to distort laterally. This brings about an increase in turbulence in the jet. The increase in the level of turbulence, in turn, leads to the emission of additional noise. The modeling and computation of the downwash, the distorted jet flow, and the excess noise radiation are the objectives of this investigation. It will be shown that calculated results at high frequencies compare well with experimental measurements.