Plasma Control for a Maneuvering Low-Aspect-Ratio Wing at Low Reynolds Number

Abstract

Plasma-based flow control was explored as a means of enhancing the performance of a maneuvering flat-plate wing. For this purpose, a numerical investigation was conducted via large-eddy simulation (LES). The wing has a rectangular planform, a thickness to chord ratio of 0.016, and an aspect ratio of 2.0. Computations were carried out at a chord-based Reynolds number of 20,000, such that the configuration and flow conditions are typical of those commonly utilized in a small unmanned air system (UAS). Solutions were obtained to the Navier–Stokes equations, that were augmented by source terms used to represent body forces imparted by plasma actuators on the fluid. A simple phenomenological model provided these body forces resulting from the electric field generated by the plasma. The numerical method is based upon a high-fidelity time-implicit scheme and an implicit LES approach, which were applied to obtain solutions on an overset mesh system. Specific maneuvers considered in the investigation all began at 0 deg angle of attack, and consisted of a pitch-up and return, a pitch-up and hold, and a pitch-up to 60 deg. The maximum angle of attack for the first two maneuvers was 35 deg, which is well above that for static stall. Two different pitch rates were imposed for each of the specified motions. In control situations, a plasma actuator was distributed in the spanwise direction along the wing leading edge, or extended in the chordwise direction along the wing tip. Control solutions were compared with baseline results without actuation in order to assess the benefits of flow control and to determine its effectiveness. In all cases, it was found that plasma control can appreciably improve the time integrated lift over the duration of the maneuvers. The wing-tip actuator could achieve up to a 40% increase in the integrated lift, above that of the baseline value.