ABSTRACT

A coupled large eddy simulation and aero-hydro-moor-servo dynamics code is used to perform numerical simulations of a floating offshore wind turbine (FOWT) under yawed conditions. The atmospheric boundary layer wind field is simulated by large eddy simulation (LES) with sufficient simulation duration as the inflow wind condition. Two cases with 15° and 30° yaw angles of wind turbine are performed, and the results of aerodynamics, hydrodynamics and wake characteristics are compared and analyzed with that of non-yaw scenario. It is concluded that the rotor power of FOWT decreases with increase of yaw angle, whereas the rotor thrust of 15° yaw angle is slightly larger than that of non-yaw situation. There is no distinct difference of platform surge motion and pitch motion between the 15° yaw angle and non-yaw scenario, whereas the two motions of 30° yaw angle are significantly less than that of non-yaw scenario. The platform sway motion increases with the increase of yaw angle due to the crosswise component of rotor thrust of wind turbine. What's more, faster wake recovery and more significant wake deflection with increase of yaw angle is observed, which is beneficial for the inflow wind condition and power generation of downstream wind turbine.

INTRODUCTION

In recent years, the wind energy has become a hot topic due to its advantages of non-pollution, renewable and rich resources (Rohrig et al., 2019). The wind energy harvesting consists of two parts: onshore and offshore. Compared to onshore wind energy, the offshore wind energy resources are more abundant, and without the limitations of land space and noise (Li et al., 2020). In addition, the most of wind energy resources are distributed in deep water area, i.e., more than 80% of offshore wind resources are available in sea area with depth > 60 m. The bottom-fixed offshore wind turbine is not suitable for deep water scenario, because the construction cost of bottom foundation will increase dramatically with the increase of water depth, which is commercially expensive and impractical. One possible solution is to change the fixed foundation to floating foundation. Consequently, in order to harvest the wind resources in deep water area and ensure it is commercially feasible, the design and development of floating offshore wind turbine (FOWT) becomes an attractive work (Ramachandran et al., 2022).

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