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

This study examined the effect of a spanwise angle of attack gradient on the growth and stability of a dynamic stall vortex in a rotating system. 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 modelling 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, increasing 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 areas of low circulation generation to areas of high circulation generation, acting to reduce local circulation and stabilise 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. Therefore, an understanding of this phenomenon has the potential to facilitate optimised wind turbine design.

Understanding Sources of Knowledge for Coaches of Athletes with Intellectual Disabilities

Background: Recent research has investigated development of coaching knowledge; however, less research has investigated the development of coaches who coach athletes with intellectual disabilities. The purpose of this study was to understand how coaches of athletes with intellectual disabilities gain their knowledge. Method Forty-five Special Olympics Canada coaches participated in structured telephone interviews investigating actual and ideal sources of coaching knowledge. Coaching knowledge was categorized across the dimensions of competition, organization and training. Results Coaches primarily learned by doing and by consulting with coaching peers. Information about ideal sources of coaching knowledge demonstrates that coaches would value structured coaching courses, learning from mentors and from administrative support, in addition to learning on their own and from peers. Discussion Results suggest that a broader approach to education should be incorporated into coaching athletes with intellectual disabilities. Recommendations for achieving such goals are provided.