Separation Control Characteristics of Synthetic Jets with Circular Exit Array

Abstract

This paper presents experimental and computational investigations on the characteristics of synthetic jets with a circular exit array. Flow characteristics of a piezoelectrically driven synthetic jet with a circular exit array have been investigated under various flow conditions. Step-by-step experiments were conducted to find an improved configuration of a circular exit array while some parameters are kept the same, such as oscillation frequency, input voltage, and exit area. Comparative studies were conducted for a quiescent condition, a forced separated flow, and a separated flow on a high angle of attack. For a quiescent condition, the jet characteristics depending on the total hole perimeter and the oscillation frequency were compared by measuring velocity profiles using a hot-wire anemometry. For a forced separated flow, pressure distributions on an inclined flat plate were examined by changing parameters, such as hole diameter, hole gap, synthetic jet array type, and oscillation phase. Experimental results were analyzed with the help of the computed vortical structures in a quiescent condition and a forced separated flow condition. Based on the comparisons, proper range of design parameters for an improved circular exit array was obtained, and it was observed that the circular exit array based on the design parameters provides a better performance in terms of separation control. For a separated flow over an airfoil at a high angle of attack, the flow control performance of a synthetic jet was verified by measuring aerodynamic coefficients. Based on various comparisons, a synthetic jet with an improved circular exit array was found to be effective for flow separation control.