Hybrid aquatic-aerial vehicles (HAAVs) are a kind of marine transportation equipment capable of operating in both aquatic and aerial environments, showing a promising prospect for marine exploration applications. This paper proposes a novel trans-medium unmanned sailboat scheme. The sailboat is driven by deformable wing sails using clean ocean energy, which can autonomously switch between surface, underwater, and aerial modes to enable multi-environment ocean exploration. Surface navigation driven by the wing sails is the main operating mode of the unmanned sailboat. Based on computational fluid dynamics (CFD), this paper focuses on analyzing the aerodynamic characteristics and propulsion performance of the parallel dual-wing sails in this mode, including structural parameters, such as aspect ratio, taper ratio, and spacing between two wing sails, control parameters, such as attack angle and sail angle, as well as the impact of flow field on the sail performance. The results indicate that when aspect ratio is between 2 and 3, taper ratio is no less than 0.6, and the spacing between two wing sails is at least 1.5 times the chord length of wing sail, the parallel dual-wing sails achieve relatively optimal aerodynamic performance. When the wind angle is less than 90°, the wing sails should be adjusted to optimal attack angle to utilize lift for propulsion. When the wind angle exceeds 90°, the upstream area of wing sails should be increased to use drag for propulsion, thereby improving propulsion efficiency. The flow field interference between two wing sails mainly manifests as blocking effects and tip vortex merging, resulting in severe imbalance in aerodynamic performance. The results provide theoretical support for profile design and surface navigation performance prediction of hybrid aquatic-aerial vehicles.
