The numerical calculation of unsteady two dimensional airloads which act upon thin airfoils in subsonic ventilated wind tunnels is studied. Neglecting certain quadrature errors, Bland's collocation method is rigorously proved to converge to the mathematically exact solution of Bland's integral equation, and a new three-way equivalence is established between collocation, Galerkin's method and least squares whenever the collocation points are chosen to be the nodes of the quadrature rule used for Galerkin's method. The computer program displays remarkable convergence with respect to the number of pressure basis functions employed, and agreement with known special cases is demonstrated. New results are obtained for the combined effects of wind tunnel wall ventilation and wind tunnel depth to airfoil chord ratio, and for acoustic resonance between the airfoil and wind tunnel walls. A new boundary condition is proposed for permeable walls through which mass flow rate is proportional to pressure jump, and promising research areas for further work are discussed.
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