Numerical study on flow field characteristics of full-scale tidal current turbines in different array configurations

The array effect of tidal current turbines (TCTs) represents a critical challenge that restricts the large-scale development of marine renewable energy. To overcome the limitations of scaled experiments and simplified models in addressing Reynolds number effects and geometric details, and to resolve the trade-offs among array configuration, wake losses, and the balance between energy capture and load stability, this study develops a high-fidelity CFD framework for a full-scale 120 kW TCT. The framework is based on Large Eddy Simulation with the WALE subgrid model. It is validated against sea-trial power output and Cp data, with the Cp deviation <1.3% at optimum TSR and quantitative error metrics of RMSE = 1.81%, MAE = 1.79%, and MRE = 3.97%. Three representative staggered configurations (2–1, 1–2, 3–2) are examined under longitudinal spacings of 1D/5D/15D and co-versus counter-rotation, focusing on power performance, wake field structures, and load fluctuation characteristics. Power spectral density analysis is further employed to reveal the nonlinear mechanisms of wake-induced interference. Results reveal a non-monotonic spacing effect: counter-rotation at intermediate spacing (5D) delivers the higher total power (438 kW of 2–1 and 435 kW of 1–2) with the smaller fluctuations, compared with the long and compact spacing. Furthermore, counter-rotation is found to effectively weaken tip-vortex coherence and suppress low-frequency load oscillations, although severe performance degradation remains unavoidable in complex multi-row topologies (3–2). Based on these findings, a hybrid design strategy coupling rotational control with geometric optimization is proposed, providing a reliable reference for the optimized configuration of large-scale TCT arrays.