The effect of longitudinal rocking motion on the wake flow of a vertical axis wind turbine

With the rapid development of offshore wind power and the tightening of nearshore site resources, floating offshore wind power suitable for deep and remote sea wind resource utilization has become the future development direction of offshore wind power in China. In vertical-axis wind turbines, the generator is located at the bottom of the entire unit. Given the high wind speeds and extreme sea conditions in deep and remote waters, vertical-axis designs, with their lower center of gravity, offer higher overall resistance to overturning in floating wind turbine applications. This paper employs Computational Fluid Dynamics (CFD) methods to study a two-blade vertical-axis wind turbine rotor. The effects of variations in pitch motion frequency on the wake characteristics of the vertical-axis wind turbine were analyzed under pitch amplitudes of 2° and frequencies of 2Hz and 5Hz, compared to the condition without pitch motion. The results indicate that pitch motion can promote the breakdown of the wake vortices; appropriately increasing the frequency can enhance the torque of the current wind turbine and accelerate the recovery speed of the wake. Additionally, this method effectively improves the negative torque resulting from changes in the angle of attack during the operation of vertical-axis wind turbines.