Complex dynamics of downwind floating offshore wind turbines due to tower shadow and platform motions

As the wind power industry expands into deeper waters and adopts floating wind turbines, downwind floating offshore wind turbines are becoming increasingly attractive due to their elimination of tip clearance requirements and improved yaw stability. However, the aerodynamic and structural complexities introduced by tower shadow effects, platform motions, and aeroelasticity present significant challenges. This study conducts a detailed simulation and analysis of a 5 MW downwind floating wind turbine using flexible multibody dynamics, actuator line method (ALM), and large eddy simulation (LES). The coupling effects of tower shadow, surge motion, and blade flexibility on the turbine’s aerodynamic performance and structural responses are investigated. Results indicate that tower shadow causes notable decreases in angles of attack (AOAs) and aerodynamic loads, leading to intensified blade vibrations and higher-order frequency oscillations. Blade vibrations result in high-frequency fluctuations in AOAs, particularly near the blade tip, which jeopardize power generation stability. Additionally, simulations reveal that platform surge motions induce periodic blade oscillations, increasing the amplitude of bending vibrations and further destabilizing aerodynamic loads. The combined effects of aeroelasticity, tower motion, and platform movement produce unique aerodynamic performance patterns, with periodic variations in thrust and torque synchronized with surge motion frequency.