Control of Separated Flow Using Actuated Compliant Membrane Wings

Abstract

Membrane wings exhibit several aerodynamic advantages at low Reynolds numbers, passively adapting to flow conditions and delaying stall to significantly higher angles of attack relative to rigid wings. Rigid wings, on the other hand, often rely on active flow control mechanisms to achieve high angles of attack, injecting momentum to induce vortex roll-up in the shear layer. Active flow control for membrane wings is limited by the flexible nature of the wing surface. However, it is possible to achieve active flow control with a membrane wing by using a dielectric elastomer actuator as the membrane material. In this work, the performance of a sinusoidally actuated membrane wing is characterized for a range of actuation frequencies, freestream velocities, and angles of attack. Lift measurements show lift enhancement of up to 20%. Time-resolved membrane kinematics are used to calculate the coefficient of added momentum of the actuator, and the effect on the flow field is shown using phase-averaged particle image velocimetry measurements. Dynamic mode decomposition is used to show vortical structures being shed from the leading edge in phase with actuation, and comparisons are made with synthetic jet literature to show the similarities to separated flow control techniques used on rigid wings.