Abstract
An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged nozzles were experimentally tested and compared. The first (reference) type of nozzle was a common sharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was assembled from these two types of nozzles—it had a rounded lip on the inside and straight section on the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were at both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate placed at a small distance downstream of the main nozzle. The actuators with particular nozzles were tested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity profiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were performed at eight power levels and at the actuator resonance frequency. The highest momentum flux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement was approximately 31% in comparison with an effect of the reference nozzle at the same input power. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters for a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated. These values were studied as functions of the dimensionless stroke length.
Highlights
Synthetic jets (SJs) are fluid flows created by fluid pulsations and are formed in free space behind a nozzle [1]
(a) evaluated synthetic jet (SJ) thrust, (b) SJ thrust divided by the jet thrust values of the reference case—nozzle A
The compound of both previous nozzles—its shape was rounded with a straight section at the nozzle nozzle type had a special design with fillets at the inner and outer nozzle exits, with a small sharp exit
Summary
Synthetic jets (SJs) are fluid flows created by fluid pulsations and are formed in free space behind a nozzle [1]. The fluid is periodically pushed and pulled through the nozzle with one end exiting into a cavity. The nozzle is the only inlet/outlet into/out of the cavity; the time-mean mass flux through the nozzle is zero. This is why SJs are often referred to as zero-net-mass-flux jets [2]. The momentum flux along the nozzle axis, is non-zero. It causes the flow to continue downstream of the nozzle exit, forming a jet flow similar to the continuous jet
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