The growing global demand for green energy requires the development of innovative solutions. Floating offshore wind turbines (FOWTs) present significant potential by enabling the harvesting of wind in deep-sea waters. However, as this technology is still in its early stages, the impact of the added six degrees of freedom (6-DOF) motion on wake dynamics and power performance remains unclear. Understanding these effects is critical for the design of floating wind farms. In this work, large eddy simulations and an actuator line model are employed to investigate the wake behavior and power output of the IEA-15MW reference turbine mounted on several floating platform concepts. To explore wake interactions in wind farm scenarios, two tandem FOWTs are modelled. The simulations are carried out in AMR-Wind, coupled with OpenFAST for the platform and blades' motion.
Initial cases are conducted with a laminar inflow to isolate fundamental wake mechanisms. Then, a neutral atmospheric boundary layer (ABL) is recreated to perform investigations with realistic offshore conditions.
Platform motions are found to induce velocity fluctuations in the wake and promote vortex-pairing. High-frequency and large-amplitude motions particularly enhance wake recovery in the upstream wake, although this effect is less pronounced in the downstream wake. Among all 6-DOF, surge is identified as the main driver of wake dynamics.
FOWTs generate larger turbulence levels than their fixed counterparts during laminar inflow. Notably, when the downstream turbine moves in phase with the incoming wake, the resulting interaction leads to the superimposition of the wake structures, forming large, separated low-speed regions.
In contrast, under turbulent conditions, FOWTs generate lower turbulence in the near wake, but similar levels further downstream. In these cases, the differences in mean wake velocity between floating and fixed turbines decrease significantly with distance.
The tandem FOWTs are found to produce less total power when operating at rated speed during neutral ABL conditions. However, the downstream FOWTs exhibit power gains of up to 20\%, indicating that larger floating wind farms are likely to generate more electricity than traditional bottom-fixed offshore wind farms.