Numerical study of the helical behavior of wind turbine wakes

Vortices helical behavior plays a crucial role in the understanding of wind turbine wakes. The behavior involves the evolution and instability of vortex systems in wakes. Here a numerical method, large eddy simulations (LES) combined with actuator line method (ALM), is used to study the vortex helical behavior and the computational geometry is based on the three-bladed MEXICO rotor with a diameter of 4.5m. Both cases (namely, tip speed ratios of 6.67 and 4.17) are simulated. Results show that vortex helical behavior in wakes is closely related to the stretching and pairing of vortices. Moreover, the behavior will impact the turbulence intensity in wakes near blade tip/root of rotor.