Effects of trim of wind-assisted propulsion ships on wing sail aerodynamic performance: A numerical study

Wind-assisted propulsion technology can effectively reduce a ship's fuel consumption and pollutant emissions. The aerodynamic performance of wing sails on wind-assisted very large crude carriers during trimming remains unclear. This study employs numerical simulation to investigate the influence of stern trim on the aerodynamic performance of a twin wing sail system. The evolution of the aerodynamic characteristics of twin sails under different trim values is analyzed. It reveals the coupling mechanisms between trim-induced geometric effects, gradient wind effects, and flow disturbance around the hull. Compared to the ship's upright condition, at stern trim values of 1, 2, 3, 4 and 5 m, the system's average thrust coefficient across all wind directions decreases by 1.5%, 1.6%, 1.6%, 1.4% and 1.4%, respectively. Furthermore, the installation position of the wing sail along the ship's length plays a decisive role in its aerodynamic performance under trim conditions. The flow field results indicate that the effect of the ship's trim on the aerodynamic performance of the wing sail is the coupling result of changes in the sail's projected area and pressure distribution caused by geometric effects, and variations in the incoming wind velocity resulting from gradient wind effects.