Offshore multi-rotor wind turbines: Blade interactions under surging conditions

The need to reduce the levelized energy cost of floating offshore wind turbines has spurred interest in scaling up rotor blades . However, this approach poses challenges related to material strength , manufacturing, and logistical hurdles in transportation. An emerging alternative is multi-rotor configurations on a single platform and tower structure. The present study concerns floating multi-rotor wind turbines operating under surge conditions. A comprehensive characterization of rotor and blade loads, power generation dynamics, and a thorough frequency domain analysis are performed within an actuator line model coupled with the OpenFOAM® Navier–Stokes solver. Results show that global loads and power generation associated with a multi-rotor configuration exhibit variability contingent upon blade azimuth and surge displacement, but heightened rotor power and loads compared to single-rotor configurations. Frequency analysis unveils the dominance of the surge frequency alongside the presence of secondary peaks attributed to rotor-to-rotor interactions. The angle of attack is shown to be primarily influenced by surge motion rather than inter-rotor interactions, underscoring the impact of platform motions on load dynamics. The outcomes of this study have significant implications for designing and optimizing multi-rotor wind turbines , particularly in mitigating load-induced fatigue effects, rendering this work a basis for further efforts in this field.