Flowfield and Noise Characteristics of Twin Supersonic Impinging Jets

A way of controlling the acoustic and aerodynamic characteristics of ideally expanded impinging twin jets has been proposed. As a means of control, microjets were used at the nozzle exit. The effect of the controlling method on the flowfield and acoustic field was investigated. Particle image velocimetry was used as the main tool for flowfield diagnostics. The results show that the predominant unsteady character of the impinging twin jets was reduced considerably by the control. Consequently at certain ground plane heights, up to 5 dB reductions in overall sound pressure level of jet noise was observed and up to 25% of the lift loss was recovered. The lift loss recovery was obtained by decreasing the entrainment of the ambient fluid into the main jet and thus lowering suction pressures on the lift plate. On the other hand, no significant effect of control on the fountain flow, which helps lift recovery with upwash, was found. [PUBLICATION ABSTRACT]