Effect of tip vortex on wing aerodynamics of micro air vehicles

Tip vortex induces downwash movement, which reduces the effective angle of attack of a wing. For a low-aspect-ratio, low-Reynolds-number wing, such as that employed by the micro air vehicle (MAV), the induced drag by the tip vortex substantially affects its aerodynamic performance. In this paper we use the endplate concept to help probe the tip-vortex effects on the MAV aerodynamic characteristics. The investigation is facilitated by solving the Navier-Stokes equations around a rigid wing with a root-chord Reynolds number of 9 x 10(4). It is confirmed that with modest angles of attack the endplate can improve the lift-to-drag ratio by reducing the drag. However, as the angle of attack becomes substantial, the wing tip vortex is stronger and the endplate loses its effectiveness. Detailed fluid flow structures are presented to offer insight into the physics responsible for the observed phenomena.