Enhanced Jet Mixing to Reduce Jet Aircraft Engine Noise

摘要

The downstream development of jet flow emanating from different nozzle shapes was investigated. This experiment was motivated by a desire to reduce the jet exhaust flow noise by increasing the mixing between the jet flow and its surroundings. Water tunnel dye flow visualization experiments were conducted on baseline straight circular cross-section nozzle, converging circular cross-section nozzle, and converging two-chevron saw tooth trailing edge nozzle. Both the converging circular and two-chevron nozzles were tapered at a 10 degree convergence angle. Flow visualization results indicated that the peak and valley geometry of the converging two-chevron nozzle modified the jet flow structure substantially. Although the jet appeared to be squeezed along the peak to peak plane, the flow escaped radially outwards in the trough to trough plane by a substantial amount. Such an expansion in the jet width is thought to enhance the mixing between the jet flow and its surroundings.