Flow characteristics of synthetic jet on torpedo shape model in cross flow

Abstract

Synthetic jet is a train of vortex rings generated by repetitive ejection and suction of fluid through an orifice. One complete cycle comprises an ejection stroke followed by a suction stroke of diaphragm. The net mass flux is zero across the orifice exit but it imparts a positive momentum to surrounding fluid. The shear layer zone of ejected fluid rolls at the orifice exit and propagates downstream due to both, momentum supplied by forward stroke and the self-induced velocity of vortex ring. In last two decades, it has gain a significant interest in range of applications like combustion, heat transfer enhancement, propulsion & maneuvering, drag reduction, jet control and boundary layer control. This study is related to the formation and characteristics of synthetic jet in cross-flow. The synthetic jet used in the present study is circular and flush mounted with the curved surface of model. The torpedo shaped model has 60 mm diameter and is placed inside the horizontal and recirculating water tunnel with test section cross sectional area equal to 400 mm × 400 mm. At flow velocities 0.072 m/s, the behavior of synthetic is investigated at three different actuation frequencies 2, 4 and 6 Hz in the range of velocity ratio equal to 1.69–4.77. The bulk flow visualization using color dye is shown in two orthogonal planes (side and top view) parallel to the cross-stream flow direction. A two-component Laser Doppler Velocimetry (LDV) technique is used for velocity measurement of synthetic jet in cross flow.