Membrane wing gust response in low Reynolds numbers

A computational study of the low-Reynolds gust response of two-dimensional rigid airfoils and elastic membrane wings is presented. Gust responses were computed via laminar Navier-Stokes simulations. For the parabolic airfoils and the thin symmetrical airfoils studied the sharp-edge gust response was similar to the Küssner function, however, it has a signature drop in the lift when the gust front reaches the trailing edge. For the thicker airfoils, the sharp-edge gust response was fundamentally different from the Küssner function. Responses to one-minus-cosine gust profiles of various amplitudes and lengths were simulated within the flow solver, and computed via convolution with the sharp-edge gust response, and with the Küssner function. Convolution with the sharp-edge gust response yielded good prediction of the simulated response, while convolution with the Küssner function yielded a poor match, thus indicating that the signature lift drop in the sharpedge gust response is significant, and is important for lift prediction by convolution. Initial results of sharp-edge gust response of an elastic membrane wing show that in general the lift buildup is similar to that of the rigid airfoil. However, the elastic membrane oscillates due to the gust perturbation, and the final lift value is larger due to the increase in camber.