Interaction of a Spanwise Non-Uniform Gust with a Flexible Wing: A Numerical Study

In recent years, there has been an increasing interest in the investigation of effects of gusts on aircraft wings using both experiments and computations. Most of these studies used rigid wings and a spanwise uniform gust to characterize the effect of different gust parameters. In the present study, the effect of a spanwise nonuniform gust on a flexible wing is investigated numerically. Three different methods were compared and contrasted with each other and with published literature: (a) where both the gust generator and wing were held fixed; (b) where the gust generator moved while the wing stayed fixed; (c) where the gust generator was fixed and the wing moved. The upper surface of the gust generator is prescribed as a velocity distribution in the form of ramp function, which maps to the surface. The velocity is turned on and off using a rectangle function that smoothly initiates and terminates the prescribed velocity distribution. By comparing the evolution of the unsteady coefficient of lift, the various gust implementation techniques are compared. Differences were found in the way the lift forces developed and in the evolution of the three-dimensional vorticity field as well. A major difference was observed in the formation and the pinching off of the leading edge vortex which formed in all the three cases considered.