Wind tunnel wall interference effects on an oscillating aerofoil in the stall regime

In order to extract aerodynamic data from multi-degree-of-freedom wind tunnel tests, it is necessary to account for various interference effects, including those of the tunnel walls. As a precursor to developing a technique for estimating wall interference effects in 3 dimensions, a 2D aerofoil undergoing oscillations in the stall regime is investigated and a means of accounting for the wall interference proposed. Computational fluid dynamics is utilized to obtain the aerodynamic load and its accuracy is assessed by comparison with published experimental data. Besides comparing the pressure distribution and lift force loops, a five parameter Leishman-Beddoes model is identified to fit the computational results. For dynamic experiments, the pressure augmentation is accompanied by an increase in lift slope during the up stroke. When tunnel wall height increases, the capability of tracking static lift tends to be improved and the model overshoot reduces. The present methodology proves to be a reliable approach to evaluate the interference of tunnel walls for 2D wings, and could be used to extrapolate the wind tunnel data to generate a free flight aerodynamic model with a good degree of efficiency and accuracy.