Wing-Gust Interactions: The Effect of Transverse Velocity Profile: INVITED

摘要

The flow field and force produced during a wing-gust encounter have been compared between a top-hat and a sine-squared transverse gusts. Experiments are performed at Reynolds number between 20 000 and 30 000 in a water tow tank. Both gusts are generated by disturbing the flow in a section of the tank at different velocities, resulting in gust ratios, GR, equal to 0.5, 0.75, 1.0, and 1.5. Time-resolved force and flow field measurements are analysed and compared with linear theories. The force results show a smoother increase in lift for the sine-squared gust accompanied by a lower maximum lift. The specific range of GRs was selected to capture the non-linear behaviour of the top-hat gust on lift. However, for the same gust ratios, the sine-squared gusts remained in the linear regime. As a result, Kiissner's theory is found to accurately predict the loads resulting from the sine-squared gust for a larger range of gust ratios than the top-hat gust. The non-linear behaviour of the top-hat gust on the lift force is linked to higher levels of circulation shed from the wing edges and the development of non-planar wakes. It is concluded that the gust shape is a critical parameter determining the wing-gust encounter characteristics.