An experimental investigation was carried out on a supersonic jet of air issuing from an M = 1.44 converging-diverging rectangular nozzle of aspect ratio 4. Particle Image Velocimetry measurements of the flow field, along with acoustic measurements, were obtained. The effects of a small amount of water (about 5 percent of the mass flow rate of the jet), injected into the shear layers of the jet, on the unsteady flow structure and sound generation were examined. The presence of the water droplets in the jet modified the turbulence structure significantly, resulting in rms velocity reductions greater than 30 percent as compared to those of a normal jet. Similar reductions of the forcing term of the Phillip's equation, which represents the generation of the pressure fluctuations in the jet, were also found. The changes observed in the near-field noise measurements, due to water injection, are consistent with the unsteady flow modifications. (Author) 13; 13
