Acoustic and heat transfer characteristics of an impinging elliptical synthetic jet generated by acoustic actuator

The acoustic aspects and average heat transfer characteristics of an elliptic synthetic jet impinging on a heated flat plate were experimentally investigated and compared with circular, rectangular and square orifices having same equivalent diameter. The aim of the study is to investigate the effect of orifice shape, aspect ratio and operating parameters of the synthetic jet at which optimum acoustic and heat transfer performance is obtained. It is found that irrespective of the shape of the orifice, the synthetic jet generates the minimum sound pressure level when operated at its resonance frequency, which is equal to the diaphragm frequency in the present case. The maximum heat transfer enhancement is obtained at the resonance frequency for elliptical orifice of aspect ratio 1.4 at the jet to plate spacing (z/de) of 3, where z is the axial distance and de is the equivalent diameter of the orifice. The aspect ratio of an orifice is a sensitive parameter as with increase in the aspect ratio, reduction in the Nusselt number is observed. For low jet to plate spacing ratios (z/de