Wind Shear, Gust, and Yaw-Induced Dynamic Stall on Wind-Turbine Blades

[摘要] This study examined the effect of a spanwise angle of attack gradient on the growth and stability of a dynamic stall vortex on a rotating blade. It was found that a spanwise angle of attack gradient induces a corresponding spanwise vorticity gradient, which, in combination with spanwise flow, results in a redistribution of circulation along the blade. Specifically, when replicating the angle of attack gradient experienced by a wind turbine at the 30% span position during a gust event, the spanwise vorticity gradient was aligned such that circulation was transported from areas of high circulation to areas of low circulation. This in turn increased the local dynamic stall vortex growth rate, which corresponds to an increase in the lift coefficient, and a decrease in the local vortex stability at this point. Reversing the relative alignment of the spanwise vorticity gradient and spanwise flow results in circulation transport from towards areas of high circulation generation, which acted to reduce local circulation and thereby stabilize the vortex. This circulation redistribution behaviour describes a mechanism by which the fluctuating loads on a wind turbine are magnified, which is detrimental to turbine lifetime and performance.

[发布机构] Department of Mechanical and Materials Engineering, Queen's University, Kingston; ON; K7L 3N6, Canada^1

[关键词] Dynamic stalls;Fluctuating loads;Lift coefficient;Local dynamics;Redistribution behaviour;Rotating blades;Vorticity gradients;Wind turbine blades