EVALUATION OF FLIP-FLOP JET NOZZLES FOR USE AS PRACTICAL EXCITATION DEVICES

This paper describes the flowfield characteristics of the flip-flop je t nozzle and the potential for using this nozzle as a practical excita tion device. It appears from the existing body of published informatio n that there is a lack of data on the parameters affecting the operati on of such nozzles and on the mechanism of operation of these nozzles. An attempt is made in the present work to study the important paramet ers affecting the operation and performance of a flip-flop jet nozzle. Measurements were carried out to systematically assess the effect of varying the nozzle pressure ratio (NPR) as well as the length and volu me of the feedback tube on the frequency of oscillation of this device . Flow visualization was used to obtain a better understanding of the jet flowfield and of the processes occurring within the feedback tube. The frequency of oscillation of the flip-flop jet depended significan tly on the feedback tube length and volume as well as on the nozzle pr essure ratio. In contrast, the coherent velocity perturbation levels d id not depend on the above-mentioned parameters. The data presented in this paper would be useful for modeling such flip-flop excitation dev ices that are potentially useful for controlling practical shear flows .