Abstract
In the last decades, Synthetic jet actuators have gained much interest among the flow control techniques due to their short response time, high jet velocity and absence of traditional piping, which matches the requirements of reduced size and low weight. A synthetic jet is generated by the diaphragm oscillation (generally driven by a piezoelectric element) in a relatively small cavity, producing periodic cavity pressure variations associated with cavity volume changes. The pressured air exhausts through an orifice, converting diaphragm electrodynamic energy into jet kinetic energy. This review paper considers the development of various Lumped-Element Models (LEMs) as practical tools to design and manufacture the actuators. LEMs can quickly predict device performances such as the frequency response in terms of diaphragm displacement, cavity pressure and jet velocity, as well as the efficiency of energy conversion of input Joule power into useful kinetic power of air jet. The actuator performance is also analyzed by varying typical geometric parameters such as cavity height and orifice diameter and length, through a suited dimensionless form of the governing equations. A comprehensive and detailed physical modeling aimed to evaluate the device efficiency is introduced, shedding light on the different stages involved in the process. Overall, the influence of the coupling degree of the two oscillators, the diaphragm and the Helmholtz frequency, on the device performance is discussed throughout the paper.
Highlights
It has been many years since Synthetic Jet (SJ) actuators have been used for active flow control, for aerospace applications
This last model inspired the work of de Luca et al [32], who provided additional analytical and numerical insights on the frequency response of SJ actuators driven by piezoelectric thin elements
Very interesting comparisons of Lumped-Element Models (LEMs) results obtained by means of both the mechanical and electric approach were showed by Sharma [31], who computed the frequency response of the devices tested by Gallas et al [23], and compared his results to the stationary solutions of Gallas et al [23], obtained applying directly the method of the electrical impedances
Summary
It has been many years since Synthetic Jet (SJ) actuators have been used for active flow control, for aerospace applications. A physical model directly based on fluid-dynamics equations has been presented by Sharma [31], who considered the oscillating wall as a single-degree-of-freedom mechanical system, while the cavity-orifice arrangement is basically described by suited forms of continuity and Bernoulli’s unsteady equations This last model inspired the work of de Luca et al [32], who provided additional analytical and numerical insights on the frequency response of SJ actuators driven by piezoelectric thin elements (among others, the prediction of the coupled resonance frequencies and the conditions to maximize the peak velocity).
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