Numerical investigation for effects of actuator parameters and excitation frequencies on synthetic jet fluidic characteristics

Numerical investigation is performed to further address the effects of geometric parameters and excitation frequency of the actuator on the synthetic jet fluidic characteristics by utilizing a two-dimensional unsteady Reynolds-averaged Navier-Stokes model. The vibrating diaphragm is modeled as a movable wall varying in sinusoidal mode. Computations are carried out by using FLUENT software with the coupled user definition function (UDF) describing the diaphragm movement. The results show that the geometric parameters of the actuator, such as the cavity depth and diameter, as well as orifice thickness and diameter, have important influences on the synthetic jet fluidic characteristics. The velocity output could be maximized if the geometric parameters of the synthetic jet actuator are designed to ensure that the cavity acoustic Helmholtz resonance frequency is coincided with the diaphragm excitation frequency. For a fixed actuator cavity, when the diaphragm excitation frequency is consistent with the Helmholtz resonance frequency of actuator cavity, the relative pressure insides the cavity is obviously great during the ejection stroke while low during the suction stroke. In the presented actuator parameters, the synthetic jet is enhanced as the decrease of cavity depth for the fixed orifice. The change of cavity diameter in the vicinity of corresponding cavity acoustic resonance diameter has relatively weaker influence on the synthetic jet. When the diaphragm is excited at high frequency, small orifice diameter will restrict the ejection and suction capacity of the synthetic jet actuator.