Plasma Control of Separated Flows on Delta Wings at High Angles of Attack

摘要

This report results from a contract tasking Institute of Theoretical and Applied Mechanics as follows: At sufficiently high angles of attack the boundary layer globally separates from the leeward surface of delta wing. The flow field contains two strong vortices generated by the roll up of the shear layer emanating from the separation lines near the wing leading edges. For supercritical angles, the vortices demonstrate a large scale instability accompanied by strong oscillations and eventual breakdown of the vortical structure. This phenomenon, called vortex breakdown or vortex burst, leads to rapid decrease of the lift to drag ratio. If the vortex burst on one wing side occurs earlier than on the other, then strong yawing and rolling moments are induced due to flow asymmetry. It is well known that the leading-edge vortex flow is extremely sensitive to variations of the surface shape and/or external forcing produced near the separation line. Such forcing can be organized by means of dielectric barrier discharge actuators which may be advantageous compared to other modern control techniques (synthetic jets, MEMS and etc.). Dielectric barrier discharge has simple construction, does not change the aerodynamic shape or influence the wing functionality when it is not in use, allows for smooth variations of forcing frequency and power, and can be used for closed loop feedback control. This kind of activation was successfully used for control of boundary-layer separation near the leading edge of a subsonic airfoil at sufficiently high angles of attack. The problem will be studied experimentally in the ITAM low-speed wind tunnel. The experiments will be performed on a delta wing model of approximately 0.5 m chord for flow speeds 10 30 m/s. The model will simulate flow features of the generic 'Stingray' UAV model tested with the synthetic-jet actuators. Tests will be conducted at chord Reynolds numbers up to 1 million , which are typical for UAV applications.