Relationship between Shock-cell Length and Noise of Jets from Rectangular and Elliptic Disk Nozzles

TLDR: In this paper, the effects of aspect ratio, measurement plane (major vs. minor) and directivity on the sound pressure levels of rectangular and elliptic disk nozzles of various aspect ratios have been analyzed.

Abstract: Jets issuing from rectangular and elliptic disk nozzles of various aspect ratios have been studied for their noise characteristics. The overall sound pressure level and directivity were measured for these jets. The effects of aspect ratio, measurement plane (majorvs. minor-) have been analyzed. The results show that the sound pressure levels are entirely different for higher and lower aspect ratio elliptic and rectangular jets. At lower aspect ratios (AR=2:1), the noise emissions from major axis plane dominate while for higher aspect ratios jets (AR>2), the noise from minor axis plane dominate. Further, the relationship between sound pressure level and average shock-cell length is observed to be quadratic at emission angles of 30° and 90° for both rectangular and elliptic jets.