Electrostatically driven synthetic microjet arrays as a propulsion method for micro flight

Abstract

A novel propulsion method suitable for micromachining is presented that takes advantage of Helmholtz resonance, acoustic streaming, and eventually flow entrainment and thrust augmentation. In this method, an intense acoustic field is created inside the cavity of a Helmholtz resonator. Flow velocities at the resonator throat are amplified by the resonator and create a jet stream due to acoustic streaming. These jets are used to form a propulsion system. In this paper a system hierarchy incorporating the new method is described and the relevant governing equations for the Helmholtz resonator operation and acoustic streaming are derived. These equations can predict various device parameters such as cavity pressure amplitude, exit jet velocity and generated thrust. In a sample embodiment, an electrostatic actuator is used for generation of the initial acoustic field. The relevant design parameters for the actuator are discussed and an equivalent circuit model is synthesized for the device operation. The circuit model can predict the lowest order system resonance frequencies and the small signal energy conversion efficiency. A representative resonator performance is simulated and it is shown that velocities above 16 m/s are expected at jet nozzles. The calculated delivered thrust by this resonator with 0.7 lm diaphragm displacement amplitude is 3.3 lN at the resonance frequency.

Axisymmetric Synthetic Jets: An Experimental and Theoretical Examination

“…Figure 17 presents the variation of the calculated virtual viscosity [Eq. (8)] of the three actuators with stroke ratio. The eddy viscosity of the equivalent continuous jet is also shown for comparison.…”

“…Additionally, the periodic vortex rings introduced into the flow exhibit an ability to influence the environment at a variety of length scales. All of these properties make synthetic jets attractive in a number of applications that include active flow control [2][3][4], electronic cooling [5,6], fluid mixing [7], and aerial [8][9][10][11] and underwater propulsion [12,13]. Although recent reviews of synthetic jets may be found in the literature [14][15][16], a brief overview of the background relevant to the present investigation is presented next.…”

Review of zero-net-mass-flux jet and its application in separation flow control

“…What is more, the ZNMF jet actuator can be highly integrated by MEMS technique with the development of material science and manufactory technique. Figure 24 presents the newly invented micro ZNMF jet actuator by Parviz et al [68] of Michigan University. The wafer contains about 1000 resonators configured in four individually addressable quadrants.…”

“…The wafer integrated with ZNMF jet actuators, next to a US quarter coin [68] . In the section at r/R=0.71, a closed recirculation flow region is formed on the surface of the stator vane down stream of the obstruction without control, and the ZNMF jet actuator just reduces the extent of the recirculation region.…”

Vacuum microfabrication on live fruit fly

“…Recent advances in microfabrication and microelectromechanical systems (MEMS) have enabled the fabrication of individual devices that can perform some of the above functions such as microactuation [1] and microsensing [2]. Other functions performed by Drosophila such as self-healing, energy storage/conversion and flight in a miniature system measuring only a few millimeters have proven more difficult to replicate [3,4]. Despite the ability of solidstate microfabrication technology to construct advanced devices, the level of complexity in multifunctional system integration inherent to Drosophila is far beyond the state-of-the-art in microengineering.…”