A novel energy conservation method for wind-assisted propulsion ships based on sails thrust optimization

The interference and aerodynamic performance of the sails are affected by changes in wind direction. Investigating the thrust optimization potential of multiple-sail systems is essential for enhancing wind energy utilization. A full-scale three-dimensional numerical simulation model of the multiple-sail system is established using validated computational fluid dynamics methods. The sail's interference and aerodynamic characteristics are analyzed across 30°–150° apparent wind direction, and found that these are closely related to wind direction. A multiple-stage optimization framework is then proposed, integrating simulation data, Kriging surrogate models, Genetic algorithms, and Expectation improvement strategies. The results show that the thrust coefficient (CT) of the sail system is effectively improved during the optimal operation, with an improvement range from 0.4 % to 10.6 %. Under bow and side winds, the aerodynamic performance of the downstream sail is enhanced through optimization, resulting in an increased CT, while the upstream sail's CT is improved at a quartering wind direction. Finally, a modified fuel consumption model is employed to evaluate the energy-saving effects of sail thrust optimization. The optimal operation resulted in a 5.4 % reduction in fuel consumption compared to the traditional synchronized approach during the Sunda Strait to Lomé, clearly demonstrating substantial energy conservation through thrust optimization.