Wake interaction of dual surging FOWT rotors in tandem

To investigate the wake interaction between floating offshore wind turbines (FOWTs), this work presents large
eddy simulations of two full-scale surging FOWT rotors in tandem. Rotors are modeled using actuator line
technique with the possibility of prescribing surge degree-of-freedom. The study examines two main aspects:
the different configurations of fixed and surging rotors, and the phase differences of surging motions when both
upstream and downstream rotors are surging. Throughout the simulations, different spacings between the two
rotors and different inflow conditions (laminar/turbulent) are explored, leading to a large database of highly
resolved simulations. The analysis of different fixed–surging configurations suggests that surging motions are
generally beneficial to the system’s power output (up to 2% at realistic turbulence intensities) compared to
the fixed configuration. The power output increase is claimed to be associated with the surging motion itself
and the faster wake recovery. Moreover, we discover that the phase differences of the surging motions have
subtle effects on the rotor performance of the downstream rotor, especially for the cases with larger spacing
between the two surging FOWTs. As an outcome, the relative difference between the power outputs are smaller
than 0.4% when the rotor spacing is five rotor diameters. With the aim that this area can be further explored,
selected animations, benchmark data, and the numerical solver developed during this study have been made
publicly available through this article.