Airfoil gust response in low reynolds numbers

A computational study of the low-Reynolds gust response of two-dimensional airfoils is presented, with an emphasis on thin cambered airfoils which are used by low-Reynolds flyers. Gust responses were computed via laminar Navier-Stokes simulations. Sharp-edge gust responses of parabolic airfoils, as well as those of thin symmetrical airfoils, were similar to the Küssner function, however, they had a signature drop in the lift when the gust front reached the trailing edge, and in general the responses were slightly higher. The concept of convolution was examined for discrete gusts of one-minus-cosine distribution and continuous sinusoidal gusts. For both gust types, the potential flow solution yielded poor predictions, while convolution with simulated sharp-edge gust response gave accurate prediction for a wide range of amplitudes, indicating that the response is linear. The role of the lift-drop, present in the sharp-edge gust response, was found to be crucial only in the prediction of highly unsteady responses to fast gusts. New approximation functions are suggested to replace the Küssner and Sears functions, for small-camber parabolic airfoils in low-Reynolds flow.