FLIP-FLOP JET NOZZLE EXTENDED TO SUPERSONIC FLOWS

An experiment studying a fluidically oscillated rectangular jet flow w as conducted. The Mach number was varied over a range from low subsoni c to supersonic. Unsteady velocity and pressure measurements were made using hot wires, piezoresistive pressure transducers, and pitot probe s. In addition, smoke flow visualization using high-speed photography was used to document the oscillation of the jet. For the subsonic flip -flop jet, it was found that the apparent time-mean widening of the je t was not accompanied by an increase in the mass flux. Fluidically osc illated jets up to a Mach number of about 0.5 have been reported befor e, but to our knowledge there is no information on fluidically oscilla ted supersonic jets. It was found that it is possible to extend the op eration of these devices to supersonic flows. The streamwise velocity perturbation levels produced by this device were much higher than the perturbation levels that could be produced using conventional excitati on sources such as acoustic drivers. In view of this ability to produc e high amplitudes, the potential for using a small-scale fluidically o scillated jet as an unsteady excitation source for the control of shea r flows in full-scale practical applications seems promising.