IL04 CHARACTERIZATION OF SUPERSONIC JET NOISE PRODUCTION AND METHODS FOR ITS SUPPRESSION

As supersonic aircraft and their turbojet engines become more powerful they emit more noise. The principal physical difference between the jets emanating from supersonic jets and those from subsonic jets is the presence of shocks in the supersonic one. This paper summarizes a study of noise reduction technologies applied to supersonic jets. The measurements are performed with a simulated exhaust of a supersonic nozzle representative of supersonic aircraft. The nozzle has a design Mach number of 1.56 and is examined at design and off-design conditions. Several components of noise are preset including mixing noise, screech, broadband shock associated noise and crackle. Chevrons and fluidic injection by microjets and a combination of them are shown to reduce the noise generated by the main jet. These techniques provide significant reduction in jet noise. PIV provides detailed information of the flow and brings out the physics of the noise production and reduction process.