Synthetic Jet Actuators with the Same Cross-Sectional Area Orifices-Flow and Acoustic Aspects

In this paper, synthetic jet actuators (SJAs) with three different orifice shapes (circular, square, and slot) with the same cross-section area were investigated. The SJA efficiency and the synthetic jet (SJ) Reynolds number were calculated based on the time-mean reaction force measurement. The momentum velocity was measured with hot-wire anemometry and additionally, the sound pressure level (SPL) was measured. The efficiency was equal maximally to 5.3% for each orifice shape, but the square orifice characterized the higher Reynolds number. The compared centerline (axial) velocities and the radial velocity profile at a distance of 112 mm were similar for each orifice type. The SPL measurement results were surprisingly constant in relation to each other. The square orifice generates the lowest SPL, approximately 2.8dB lower than the circular orifice, and approximately 4.2dB lower than the slot orifice, at each investigated real power. Finally, the differences to other papers and limitations of the approach to comparing orifices presented in the present paper were indicated.