An axisymmetric synthetic jet actuator based on a loudspeaker and five types of flanged\nnozzles were experimentally tested and compared. The first (reference) type of nozzle was a common\nsharp-edged circular hole. The second type had a rounded lip on the inside. The third nozzle type was\nassembled from these two types of nozzlesâ??it had a rounded lip on the inside and straight section\non the outside. The fourth nozzle was assembled using orifice plates such that the rounded lips were\nat both inner and outer nozzle ends. The last nozzle was equipped with an auxiliary nozzle plate\nplaced at a small distance downstream of the main nozzle. The actuators with particular nozzles were\ntested by direct measurement of the synthetic jet (SJ) time-mean thrust using precision scales. Velocity\nprofiles at the actuator nozzle exit were measured by a hot-wire anemometer. Experiments were\nperformed at eight power levels and at the actuator resonance frequency. The highest momentum\nflux was achieved by the nozzle equipped with an auxiliary nozzle plate. Namely, an enhancement\nwas approximately 31% in comparison with an effect of the reference nozzle at the same input\npower. Furthermore, based on the cavity pressure and the experimental velocity profiles, parameters\nfor a lumped element model (mass of moving fluid and pressure loss coefficient) were evaluated.\nThese values were studied as functions of the dimensionless stroke length.
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