Two new fluidic actuator designs were developed to control fluid flow in ways that will ultimately result in improved system performance and fuel efficiency in to improve the aerodynamic performance of a variety of vehicles. These flow control actuators, often referred to as fluidic oscillators or sweeping jet actuators, utilize the Coanda effect to generate spatially oscillating bursts (or jets). They can be embedded directly into a control surface (such as a wing or a turbine blade) to help reduce flow separation, increase lift, reduce drag, enhance mixing, or increase heat transfer. Recent studies show up to a 60% performance enhancement (such as increased lift or reduced drag) with fluidic actuators.

One of the actuator designs effectively decouples the oscillation frequency from the amplitude (i.e. mass flow through the actuator). A decoupled actuator can deliver high mass flow rates without changing the frequency, or deliver high- or low-frequency oscillating jets at minimal mass flow rates. The second actuator design enables inphase or anti-phase synchronization of the oscillating jets. This overcomes issues caused by the random oscillation of individual actuators when they are used in an array of actuators, and has particular benefit for flow-control applications. These new designs will provide better control authority over the fluidic actuator, increased actuator efficiency, decreased mass flow, and improved system performance.

The new actuator designs do not require any additional equipment—oscillations, decoupling, and synchronization are achieved in a passive manner, entirely via internal flow dynamics. Since these actuators have simple and compact structure and do not have any moving parts, they are basically maintenance- free, and highly scalable. They can be manufactured from many different materials and therefore can also be used in harsh environments.

This work was done by Mehti Koklu of Langley Research Center. LAR-18089-1/90-1

Motion Control & Automation Technology Magazine

This article first appeared in the June, 2014 issue of Motion Control & Automation Technology Magazine.

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