Abstract
The structure of the flow behind a three dimensional aerofoil, which performs pure heaving oscillations, is examined for a flow Reynolds number of 164, and heaving Strouhal numbers between 0.2 and 0.4. Dye flow visualization is used to study the flow from the front, side and rear of the aerofoil. A comparison with the flow around an infinite-span aerofoil with the same thickness and chord, and which operates at the same Reynolds number and Strouhal numbers, reveals that the three dimensional and two dimensional heaving aerofoil flows are substantially different. The structures in a two dimensional foil flow are predominantly orientated along the spanwise direction. In contrast, v-shaped vortex structures, which are partially aligned with the aerofoil wingtips, are formed in a finite-span aerofoil flow.