An improved panel method for unsteady aerofoil flows

This paper presents some improvements to a low-order panel method for computing unsteady, inviscid, incompressible potential flows. An explicit Kutta condition for equalization of the trailing edge pressures is defined and implemented iteratively in a linearised form yielding improved prediction of pressures at the trailing edge. The wake shedding model, which possesses an arbitrary parameter for this type of low-order method, is also examined and a method for removing the indeterminacy of the wake-shedding parameter on a rational basis is put forward. These improvements are incorporated into a two-dimensional panel method and results obtained for a NACA0012 section in transient and oscillatory motions. Results are compared with those from a moving-mesh finite-volume Euler solver for incompressible flow, and the two methods are shown to agree closely for the lift and pitching moment predictions, while comparison of the computed wakes shows major differences. Additional results are also shown for the panel method for the case of the convection of a point vortex past a moving aerofoil and its wake.