General Reduced-Order Model to Design and Operate Synthetic Jet Actuators

Synthetic jets are used in various applicat\nions from flow contro\nl to thermal management\nof electronics. Controlling the jet operating\npoint using a simple voltage to velocity\ncalibration becomes unreliable in case of ext\nernal pressure field disturbances or varying\nactuator characteristics. This paper pres\nents a general lumped parameter model for a\nsynthetic jet actuator with electromagnetic\nor piezoelectric driver. The fluidic model\naccurately predicts the synthetic jet operati\nng point (i.e. Reynolds number and stroke\nlength) based on the measured cavity pre\nssure. The model requires only two empirical\ncoefficients characterizing\nnozzle fluid damping and inertia\n. These can be obtained via\ncalibration or estimated from pressure loss co\nrrelations and the governing acoustic radiation\nimpedance. The model has been validated\nexperimentally for a ci\nrcular and rectangular\norifice. The effect of nozzle damping on\nthe nonlinear system response is discussed.\nAnalytical expressions are given for the two resonance frequencies characterizing the system\nresponse, as a function of the diaphragm a\nnd Helmholtz resonance frequencies. The optimal\ndesign of an impinging synthe\ntic jet actuator is discusse\nd in terms of the thermal and\nacoustic efficiency. Guidelines for selectin\ng the optimum combination of diaphragm and\nHelmholtz resonance frequency are presente\nd and compared to previous studies.