Principles of a High-Bandwidth Microactuator Producing Supersonic Pulsed Microjets

This paper explores the principles of a high-bandwidth microactuator that potentially can be used for the active control of high-speed shear and boundary layer flows. The microactuator is capable of producing pulsed microjets at a desirable frequency (1-60 kHz), with high unsteady momentum and energy suitable for controlling the unstable structures of supersonic flows. In principle, the actuator consists of a source microjet that underexpands into a cylindrical cavity with multiple micro-nozzles at the opposite side through which the unsteady microjet array emanate. A lumped element modeling (LEM) approach is used to explore the characteristics of the actuator. The natural resonance frequency of the actuator system is derived from the basic principles of physical acoustics and compared with the experimental data for actuators with different geometries. While good agreement is found for cavity volumes of less than 5 mm 3 and the overall trend is correctly predicted, the deviations for large actuator cavities are significant, suggesting that model refinement is needed for handling these cases.