Considering the shortcoming and inability of the conventional piezoelectric synthetic jet actuator (PE-SJA), a novel multi-diaphragm PE-SJA was designed and made in this paper, and some detailed experimental study was carried out upon it. Using the hotwire anemometry, the optimum resonance frequency of the actuator was obtained. Then, under this special frequency, velocity magnitude was measured at different positions along the axis of the orifice. And then the orifice exit velocity of different numbers of diaphragm was measured, analysized and compared, which showed that the mean and peak axis velocity of one diaphragm PE-SJA were only the half of those of the five diaphragms PE-SJA., while the performance of three diaphragms PE-SJA was almost the same as that of the five diaphragms., which meant that although the performance of the PE-SJA increased with the number of the piezoelectric diaphragm, it was not in linearly ways. From the experimental result it was also shown that: For frequency f = 560Hz, the optimum diameter and depth of the orifice was 2.5mm and 2mm, respectively. Therefore, the optimum depth/diameter ratio was 0.8 for the present actuator and frequency. And then the performance of the multi-diaphragm PE-SJA with taper-jet exit orifice was much better than that of the straight orifice. Finally, the PIV was used to measure the structure of vortex of the flowfield.

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