The Use of Small Air Jets to Simulate Metal Chevrons

This is a brief summary of numerical and experimental studies, conducted between about 2003 and the present, on various types of injection methods for jet noise reduction. The work included studies of both water and air microjets and a number of different aerodynamic or fluidic chevron designs. The experimental tests were run in a subscale dual-stream nozzle facility using nozzle geometries that were representative of full scale engines. The facility had the capability of simulating full scale total pressures and temperatures, with free-stream velocities up to about Mach 0.28. During the course of this work, it was discovered that aerodynamic chevron nozzles could be designed that did not require the use of an auxiliary air supply. The study of these new nozzle designs then became the main focus of the work and is the main emphasis of this paper. It is shown that this new nozzle design is very flexible and can give significant noise reduction for a variety of applications. I