Abstract: Hybrid aquatic-aerial vehicle (HAAV) is a kind of marine transportation equipment that can operate in both aquatic and aerial environments, and holds a bright prospect for marine exploration applications. This paper firstly proposes a novel trans-medium unmanned sailboat scheme. The sailboat is driven by deformable wing sails using clean energy from the ocean, which can autonomously switch between surface, underwater, and air modes to enable multi-environment ocean exploration. For the unmanned sailboat, driving on surface by the wing sails is the main navigation mode. Based on Computational Fluid Dynamics (CFD), this paper will focus 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 of two wing sails, control parameters, such as attack angles and sail angles, as well as the impact of flow field on the wing sails performance. The results indicate that when aspect ratio is between 2 and 3, taper ratio is not less than 0.6 and spacing of two wing sails is at least 1.5 times the chord length of wing sail, the parallel dual-wing sails can 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. Meanwhile, when the wind angle exceeds 90°, the upstream area of wing sails should be increased to use drag for propulsion, then the wing sails can obtain a higher propulsion efficiency. The flow field interference between two wing sails is mainly manifested as blocking effect and tip vortex merging, leading to a serious aerodynamic performance imbalance. The research results can provide theoretical support for profile design of the hybrid aquatic-aerial vehicle and prediction of its surface navigation performance.

Key words: unmanned sailboat, parallel dual-wing sails, aerodynamic characteristics, interference effect, transmedia