Flight effects on the far-field noise of a heated supersonic jet

The influence of forward flight on the far-field noise of an underexpanded heated supersonic jet has been studied experimentally with a 12.5-cm-diam convergent nozzle operated in the NASA Ames Research Center 12.2 X 24.4 m (40 X 80 ft) wind tunnel. The nozzle was operated at nozzle pressure ratios up to 4.5 and stagnation temperature ratios from 2.45 to 3.45. The resulting velocity (based on fully expanded condition) range is from 586 to 858 m/s. The freestream Mach number was varied from 0 to 0.32. Par-field narrow band spectra were obtained at angles (measured from the inlet axis) covering a range from 30 to 155 deg. A small amplification of the overall sound pressure level (2 dB) due to forward flight is observed in the forward quadrant. The mixing noise reduction in the aft quadrant due to forward flight is much smaller than that observed in corresponding cold jets.