Offshore multi-rotor wind turbines : tandem turbine interactions

Abstract

Multi-rotor turbines are emerging as a promising upscaling solution for offshore wind farms, yet optimization of these systems, particularly in floating configurations, has received limited attention in the literature. This study examines the wake recovery and performance of tandem, floating multi-rotor turbines under surge motion, focusing on wake velocities and dynamic loads experienced by a quad-rotor system. Using a validated actuator line model, multiple realistic surge conditions are simulated to assess the effects of motion kinematics on wake behavior and rotor performance. It is demonstrated that tandem quad-rotor systems exhibit superior wake recovery compared to single rotors, due to enhanced mixing and faster wake diffusion. While surge motion has minimal effect on average power and thrust coefficients, particularly at low frequencies, it significantly impacts the wake structure and increases dynamic loads. Findings also indicate that quad-rotor configurations can mitigate wake effects, improving wind farm efficiency and reducing the risk of dynamic load-induced fatigue. Thus, insights into wake dynamics and rotor interactions from this study can practically guide the design and operation of future offshore wind farms providing new insights on how surge motion influences wake recovery and blade loads in such environments.