Flow Topology of Laminar Separation and Reattachment on a Wall-Bounded Wing

Airfoil performance at transitional Reynolds numbers depends strongly on the dynamics of boundary layer separation and reattachment. Though it is convenient to assume two-dimensional flow, recent evidence suggests wing-wall junctions affect transition dynamics, particularly for low aspect ratio wings. Here, a NACA 65(1)412 airfoil with aspect ratio $AR=3$, is set between two end walls, and at $alpha = {0, 2, 4, 6, 8, 10}^{circ}$, with Reynolds number, Re$_c = {2, 4, 6, 8} imes 10^4$. Two-dimensional PIV is used to quantify the flow topology at midspan, the end walls, and within the boundary layer of the airfoil suction surface. Both spanwise and chord-normal directions are investigated. A curved laser sheet is employed to capture the flow at the suction surface in the spanwise-streamwise directions. The line of laminar separation depends only weakly on Re, and inside the separation region, spanwise velocities up to $0.2U_{infty}$ are found. The flow is never two-dimensional, and implications of this for control strategies are considered.