Large-eddy simulation of the influence of hairpin vortex on pressure coefficient of an operating horizontal axis wind turbine.

• Effect of dynamic hairpin vortex on C p is dissected. • Mechanism of rotational augmentation on hairpin vortex formation is elucidated. • Driving mechanism of streamwise vortex evolution into hairpin vortex is revealed. • Evolution process of streamwise vortex into hairpin vortex is captured. • Role of primary hairpin vortex in promoting secondary hairpin vortex is clarified. The formation, evolution, and shedding of vortices around the blade of a rotating wind turbine affect the aerodynamic pressure distribution on the blade surface and consequently, the wind turbine output power. The mechanism of blade surface vortex flow affecting aerodynamic pressure is the basis of analyzing aerodynamic characteristics of wind turbines, which is of great significance to evaluate and guide the improvement of the aerodynamic performance of wind turbines. Combined with the large-eddy simulation (LES) and dynamic Smagorinsky model, the local mesh refinement in the rotating domain is used to analyze the evolution details of a streamwise vortex into a hairpin vortex. It is found that the streamwise vortex with a certain angle to the chord appears near 0.5C when the air passes through the blade's leading edge; the closer it is to the blade tip, the greater the inclination. In the radial region of 0.7–0.8R, the coupled effect of Coriolis and centrifugal forces enhanced by rotation increase the spanwise velocity and evolution of some streamwise vortices into hairpin vortices, so that the streamwise vortices and hairpin vortices play a dominant role in trailing edge vortices. This dramatically increases the trailing edge adverse pressure gradient, thus contributing to the improve the turbine aerodynamic performance. The results indicate that the coupled variation of Coriolis force, centrifugal force, and angle of attack affects the generation and evolution of the hairpin vortex, which in turn affects the aerodynamic performance of the wind turbine, providing new perspectives for the improvement of aerodynamic performance. [ABSTRACT FROM AUTHOR]