Unsteady Aerodynamic Response of a Flat Plate Encountering Large-Amplitude Sharp-Edged Gust

Abstract

This study presents numerical findings of the response of a flat plate to transverse, sharp-edged gusts at a low Reynolds number (). A split velocity method was implemented in a three-dimensional Navier–Stokes solver to simulate a rigid flat plate wing at steady velocity and 0° angle of incidence encountering a sudden sharp-edged gust. The gust perturbations in the flow domain were prescribed to the grid points, and source terms were added to the governing equations to account for the full interaction between the wing and the gust. Two sharp-edged gust profiles are considered: 1) a top-hat profile gust of finite width and 2) a step profile gust of infinite width. The gust amplitude varies from 4 to 120% of the freestream velocity (). The split velocity method was found to be capable of capturing the physical phenomenon of flat plate undergoing sharp-edged gust, and the predicted lift coefficient is found to be in good agreement with that of experiments. The duration and magnitude of the wing–gust interaction were both found to affect the airfoil response. In the step gust encounter, the lift behaves similarly to that predicted by the Küssner’s model for small-amplitude gusts where . The lift buildup is nonlinear for larger gust amplitudes where . Convolution with the computed step gust response shows good agreement with the simulated response during long and large gust encounters. However, both computational fluid dynamics and Küssner-convolution-based methods fail to predict the exit phase from gust and the recovery to a steady-state value.