The impact of pitch motion of a platform on the aerodynamic performance of a floating vertical axis wind turbine

The flow-field around the offshore floating vertical axis wind turbines (OF-VAWTs) is affected by the six-degrees of freedom (6-DOF) movement of the platforms. Understanding the impact of a certain DOF motion on the aerodynamics is beneficial to the design of wind turbines. In this paper, the aerodynamics and performance of a scale OF-VAWT in pitch motion are investigated. The computational fluid dynamics (CFD) method with the turbulence model of improved delayed detached eddy simulation (IDDES) and the overset mesh technique are employed to analyze the characteristics of pitch motion of wind turbines. The CFD model is verified by the experimental data from available literature when the turbine has no-pitch motion. Then, the aerodynamic forces, power, and wake of an OF-VAWT in periodical pitch motion are analyzed. Because of the varying wave loads, an unsteady aerodynamic analysis considering the pitch motion with different periods and amplitudes is performed. The results show that the pitch motion can improve the power output of the OF-VAWTs, and enlarge the variation ranges of aerodynamic force coefficients. Meanwhile, the graphs of the vortex structure show that the complex flow interaction emerges around the rotor blades. Additionally, the power coefficient and the instantaneous aerodynamic forces coefficients sensitively change with different pitching periods and pitching amplitudes.