A synthetic jet actuator, which can be micromachined if desired, generates a synthetic jet stream characterized by a series of successive vortices that can be used for effectively entraining adjacent fluid. The synthetic jet actuator can be used to bend, or vector, a jet stream from another jet actuator. Further, because the synthetic jet actuator exhibits zero net mass flux, the synthetic jet actuator can be used within a bounded volume. In structure, the synthetic jet actuator comprises a housing defining an internal chamber and having an orifice. A flexible metallized diaphragm forms a wall of the housing and can change the volume of the chamber when moved. An electrode is disposed adjacent to and spaced from the diaphragm, and an electrical bias is imposed between the metallized diaphragm and the electrode by a control system to force movement of the diaphragm. As the diaphragm moves, the volume in the internal chamber changes and vortices are ejected from the chamber through the orifice.

Synthetic jet actuator and applications thereof

Briefly described, the present invention is concerned with cooling heated bodies and/or heated fluid with synthetic jet actuators in either open or closed systems. A first preferred embodiment of a cooling system of the present invention comprises a synthetic jet actuator directed to impinge directly on a heat producing (or heated) body. The synthetic jet actuator generates a synthetic jet stream comprised of cool ambient fluid that impinges on the heated surface thereby cooling this surface. As an example, the heated surface/body could be a microchip array in a microcomputer. After coming into contact with the heated surface, the fluid moves along the surface and is finally rejected to the ambient where it mixes and cools down. The synthetic jet may be incorporated into a modular unit that may be clipped on to a circuit board or other heat producing element to provide added, `ad hoc` cooling. In another configuration, a synthetic jet actuator may be positioned, relative to the heated surface, to create a synthetic jet stream to flow along the heated surface. In this embodiment, the flow would be approximately tangential to a surface of a heat producing body. This embodiment may further comprise a cyclical flow of the fluid jet, along the heated body and about a heat sink surface.

Synthetic jet actuators for cooling heated bodies and environments

The present invention involves micromachined synthetic jet actuators, or “microjet” actuators. These fluidic control devices may be fabricated using standard silicon micromachining techniques and comprise an orifice situated atop an actuator cavity which is bounded at least partially by a flexible membrane. Alternatively, microjets may be formed in more robust substrates, such as metals or ceramics. Vibration of the membrane using either electrostatic or piezoelectric drives results in a turbulent air jet formed normal to the microjet orifice. The jet stream is synthesized by a train of vortex rings. Each vortex is formed by the motion of the diaphragm and is advanced away from the jet under self-induced velocity. Alternatively, the microjet actuator can comprise a “piston in cylinder” to take the functional place of the vibrating diaphragm. This can be accomplished by changing the aspect ratio of the actuator cavity to a deeper, more cylindrical shape. A piston-like actuator can then be realized by using a “bossed” diaphragm. An improvement to microjets is the use of modulators with the jet actuators. Modulators are generally devices to selectively cover and uncover the orifice of a synthetic jet actuator in order to prevent either flow into or out of the jet cavity. Such modulators are fabricated as either vertical drive, lateral drive or constricting modulators.

Micromachined synthetic jet actuators and applications thereof

An active perturbation-producing element on the solid surface is driven to induce oscillations in the boundary layer of the fluid stream about an axis substantially perpendicular to the solid surface, to enhance the mixing of the boundary layer in the fluid stream. The method is particularly applicable for increasing the lift of a wing, but may also be used for increasing the divergence angle of a diffuser.

Method and apparatus for delaying the separation of flow from a solid surface

An LED assembly is provided herein. The assembly comprises a thermally conductive housing (201), wherein a portion of said housing is equipped with a plurality of fins (203); an LED (205) disposed in said housing; and a synthetic jet actuator (207) adapted to direct a synthetic jet onto said portion of the housing.

Synthetic jet cooling system for LED module

The lift generated by delta wings is due primarily to large vortices associated with the flow separation near the leading edge. The invention includes a perturbation device to control the separation shedding of those vortices and manipulate their frequency and pairing. This results in different growth rates of the vortices downstream of the device and thus the lift produced by the large bound vortices may be controlled. If the invention is applied to both leading edges, the total lift of the wing will be altered; if the perturbation is preferentially applied on only one side of the wing, the moment around the roll axis of the aircraft is controlled. A first embodiment uses a piston coupled to a cavity and slot to produce the desired perturbation. Alternative embodiments are described which achieve the results without moving parts.

Randy A. Srnsky

Papers

Method and apparatus for controlling bound vortices in the vicinity of lifting surfaces