Fluid-structure coupling effects in synthetic jet devices

The operation of a synthetic jet actuator driven by a thin piezoelectric disk is both analytically and numerically investigated by means of a lumped element mathematical model, in order to obtain information about the frequency response of the device. It is shown that the actuator behaves as a two-coupled oscillators system and simple relationships are given in order to predict the two peak frequencies, corresponding to the modified Helmholtz and first-mode structural resonance frequencies. The model is validated through experimental tests carried out on three devices having different mechanical and geometrical characteristics, designed primarily to achieve an increasing coupling strength. A strict agreement between overall theoretical scaling laws and numerical computations is also found.