Objective Predicting and assessing the aerodynamic performance and propulsion effect of rotor sails is crucial during the preliminary design phase for selecting the appropriate rotor configurations for ship applications.

Method First, unsteady-state numerical simulations of the aerodynamic performance of the rotor were performed using the computational fluid dynamics (CFD) method, with the reliability of the model validated against experimental data. Second, the influence of the foundation structure on the rotor's aerodynamic performance was investigated. Based on these findings, the aerodynamic characteristics of rotors with cylindrical foundations, under varying aspect ratios and diameter ratios, were systematically calculated and compared. Finally, the available power of rotors with different diameters at a fixed height was calculated and compared for power assessment.

Results The presence and structure of the foundation significantly affect the flow field distribution beneath the rotor, leading to a reduction in the extent of the low-pressure region on its surface and a decrease in the lift coefficient. Compared to the rotor without a foundation, those with cylindrical and square foundations show reductions in lift coefficient of 17.7 % and 25.5 %, respectively, at a velocity ratio of 4.5. When the rotor height is fixed, there exists an optimal aspect ratio (i.e., optimal diameter) that maximizes the available power of the rotor.

Conclusion The results of this study provide valuable insights for the design matching, optimal selection, and performance evaluation of marine rotor sails.