Effect of temperature on supersonic jet noise

Abstract

The influence of temperature on the sound field of supersonic, shock-free jets is studied experimentally by measuring the turbulent mixing noise in the far field from four 2-in.diam nozzles, operated in a carefully designed anechoic room that provides a free-field environment. The nozzles were operated at pressure ratios up to 7.4 and over the range of stagnation temperature ratios from unity to 3.3, thus providing exit velocity ratios in the range 0.35 to 2.8. To minimize the additional problems of convective amplification and refraction, the effects of temperature on mixing noise source strengths per se are established by examining the data at 90° to the jet axis only. In general, two sources of noise are apparent, one resulting from the familiar Reynolds shear stress fluctuations and a second attributable to density or temperature fluctuations promoted by the turbulent mixing of streams of dissimilar temperatures. Scaling laws for the velocity and temperature dependencies of the spectra of these noise components are derived and tested. Further, it is shown that these sources are not statistically uncorrelated as Presented as Paper No. 73-991 at the AIAA Aero-Acoustics Conference, Seattle, Wash., Oct. 15-17, 1973. This study forms a part of the larger program on supersonic hot jet noise research conducted at Lockheed-Georgia Co. and financed by the Air Force Aeropropulsion Laboratory and the U. S. Dept. of Transportation under Contract F33615-73-C-2032. Research Scientist. Senior Lecturer, University of Southampton; also Consultant to Lockheed-Georgia Company.