Microjet-Based Active Flow Control on a

A fixed wing, remote controlled, unmanned aerial vehicle (UAV), has been retrofitted with a system of microjet-based actuators to test microjet efficacy for flow control during flight. This allows one to evaluate the flow control system in a more complex and uncontrolled environment relative to the “clean” laboratory flowfield. The system is composed of off-the-shelf components and provides some appreciation of the challenges associated with implementing such an active control scheme in more “practical” configurations. A wing section with actuators was first tested in a low-speed wind tunnel to characterize microjet control efficacy in the laboratory using surface flow visualizations and particle image velocimetry (PIV). The laboratory results show that the microjet actuators are an effective means of controlling separation with fairly low supply pressures and flow rates. Only relatively robust and straightforward diagnostics can be used to determine the flow conditions on the UAV during flight. As such, tufts are installed on the aircraft’s wing to serve as a qualitative way of measuring control efficacy. Results from the flight tests confirm that this flow control system is capable of delaying flow separation in the complex flows occurring during flight.