Wind tunnel investigation of jet interference for underwing installation of high bypass ratioengines

Abstract

Current design proposals for many swept-winged aircraft have large engines of high bypass ratio wih short fan cowls on short pylons under the wing, with the annular fan nozzle close to the wing leading edge. With such an arrangement there may be significant changes in the wing pressure distribution induced by the jet flow, particularly that from the fan. In consequence, the normal method of simulating the engine flow in a wind tunnel model, by using simple open ducts, and no representation of the jet thrust, might not be adequate. The tests reported here were planned as an initial investigation of jet interference for this type of configuration. Results show that for conventional locations of the nacelle on the wing, representation of the cruising jet thrust has only a small effect upon the wing pressure distribution and then only on the lower surface.