Towards controlling the three-dimensional wall jet development

Preliminary results are presented from a study aimed at manipulating the width of a three-dimensional wall jet. Single-point velocity measurements of the wall jet development were obtained at 15 outlet diameters downstream using hot-wire anemometry for both the uncontrolled and cases. The present actuation system consists of 6 synthetic jet actuators evenly distributed around the periphery of the jet nozzle and with all of the actuators operated in phase. Various excitation frequencies at multiples of the jet column mode were employed. This actuation methodology was found to successfully enhance the width of the three-dimensional wall jet. Moreover, actuation at one half of the frequency associated with the column mode instability, and not the column mode itself, produced the widest wall jet The relationship between the jet half widths and the maximum velocity in the excited cases proved to be quite complicated, indicating that the excitation did not simply cause the jet to develop slower. The results suggest that measurements in the full cross flow plane are required to understand the full effect that excitation has on the flow.