Dynamic Performance of Parallel Dual-Wing Sails for an Unmanned Sailboat with Multiple Navigation States

Unmanned surface vehicles (USVs) play a crucial role in various fields, including ocean climate change monitoring, marine resource exploitation, and ecological environment exploration. Out of the many types of USVs, unmanned sailboats have gained considerable attention for their ability to conduct green, large-scale ocean observations. Building on this concept, this paper proposes an unmanned sailboat propelled by parallel dual-wing sails, which is designed to meet the demands of extensive and three-dimensional marine comprehensive observation and data collection. With a focus on the parallel dual-wing sails, this study particularly investigates the effects of variations in the airfoil’s angle of attack and the impact of the spacing ratio between the dual sails on propulsion performance. It further analyzes the influence of one sail’s angle of attack on the performance of the other sail, as well as the flow field between the two sails. For the air navigation and underwater states, the force characteristics of the dual sail under different inflow velocities were investigated. The research findings indicate that, under certain conditions, the thrust coefficient exhibits a trend of first increasing, then decreasing, and finally increasing again with alterations in the angle of attack α. Different single-sail angles of attack have varying impacts on the opposite sail and the flow field between the dual sails. Moreover, the generated forces are positively correlated with inflow velocity in the air navigation and underwater states. The findings reveal that it is possible to reduce drag, mitigate the adverse effects of sail interaction, and thereby enhance the propulsion performance and overall navigational stability of the sailboat by applying an optimal spacing ratio design and adjusting the angle of attack and inflow velocity.