Rotor configuration effects on coupled aero-hydro-mooring dynamics of spar-type floating vertical axis wind turbines

The selection of the rotor configuration for floating vertical axis wind turbines (VAWTs) plays a major role in their energy capture efficiency and structural reliability. The objective of this work is to investigate the differences in performance between different rotor configurations and to clarify the dominant coupling mechanisms under floating conditions. A high-fidelity computational fluid dynamics (CFD) framework is established by combining dynamic fluid-body interaction (DFBI) and volume of fluid (VOF) models to capture the fully coupled aero-hydrodynamic response. A comparative analysis of full-scale H-type and Φ-type floating VAWTs with the same swept area is performed. The results show that the more compact support structure of the Φ-type rotor reduces flow losses, leading to a higher time-averaged power coefficient of 0.378, compared with 0.201 for the H-type rotor. Although the H-type rotor generates higher torque on the upwind side, its overall power output is weakened by downwind torque fluctuation, tip-vortex effects, and support-arm interference. The wake of the H-type rotor shows stronger flow disturbance and lateral diffusion, while the Φ-type rotor maintains a more coherent downstream wake due to its closed blade-end connections. Due to its larger upwind projected area, the thrust coefficient of the H-type rotor is approximately 9% higher than that of the Φ-type rotor, resulting in larger surge drift and a redistribution of mooring tensions. These findings provide guidance for the rotor–platform integration of floating VAWTs and highlight key design trade-offs that should be considered in future large-scale offshore deployments.