Scarfed Nozzle for Jet Installation Noise Reduction

The effects of scarfed nozzles on the jet-installation noise were experimentally investigated using unheated subsonic jets in an anechoic jet noise facility. The experiments were carried out for four different types of scarfed nozzles with increasing nozzle lip angles. Installation effects were investigated at a plate distance of one jet diameter away from the jet for Mach numbers ranging from 0.3 to 0.8. The use of scarfed nozzles has been known to deflect the flow away from the center axis and induce asymmetry in the jet shears leading to azimuthal variation in the spectra and thus noise reduction. In this study, the possibility of jet-installation noise reduction with the use of scarfed nozzleshas been explored at subsonic flow conditions. The characteristics of the jet hydrodynamic pressure fluctuations were investigated in the axial direction using far-field measurements. The near-field flow features were studied using surface pressure transducers installed on the flat plate for the installedconfigurations. Detailed spectral, coherence, and correlation analysis were carried out to determine noise reduction mechanisms involved with scarfed nozzles at the proximity of a flat plate.