Analysis of Aerodynamic Performance and Application of Flettner Rotor

Ships equipped with rotating sails may generate propulsion by harnessing wind energy. The ability to regulate the spinning sails is essential for reducing ship emissions and conserving energy. This article examines the aerodynamic performance, thrust, net power, and energy-saving impact of a rotating sail (rotor) at various actual wind speeds and wind angles from the standpoint of practical application using Computational Fluid Dynamics (CFD) technology based on the Magnus effect. The study’s findings indicate that: the rotor's aerodynamic performance has a nonlinear relationship with the wind direction angle and is positively correlated with the true wind speed; the lift-drag coefficient is negatively correlated with the wind direction angle and positively correlated with the true wind speed. The 90° wind direction angle is where the lift-drag ratio and the lift-drag coefficient indicate an inflection point. The study also discovered that the energy-saving impact improves with increasing real wind speed at the same wind direction angle. The rotary sail's greatest energy-saving impact happens at a real wind direction angle of 90°, regardless of wind speed. The highest energy-saving result of installing a rotating sail can be up to 7.7% while the ship is sailing against the wind at a speed of 18 knots (wind speed of 10 m per second). On the other hand, under some unique situations, using the rotor will result in increased motor power consumption rather than a navigational assistance benefit. The study's findings can serve as a guide for those designing and implementing rotating sails, as well as for ship captains adjusting sails to maximize efficiency.