A hybrid-driven underwater glider (HUG) is a new type of unmanned underwater vehicle which combines the advantages of traditional underwater gliders (UGs) and autonomous underwater vehicles (AUVs). In this paper, a new design scheme, equipping a foldable wing module on the top of the HUG, is proposed to reduce the drag force generated by the wing in AUV mode. And the effect of wing position lifting on the motion performance in UG mode is studied by computational fluid dynamics (CFD) methodology and motion simulation. The results show that the wing lifting reduces the lift force of the glider and increases the drag force. But the wing lifting makes the movable block movement distance smaller, which is required for the glider to reach the target gliding angle.
An underwater glider (UG) is a special type of autonomous underwater vehicle which is controlled by adjusting its buoyancy. For the characteristics of low energy consumption, low cost and long range, several typical UGs have been developed and broadly applied in physical and biological oceanography, such as Slocum (Webb, 2001), Spray (Sherman, 2001) and Seaglider (Eriksen, 2001). The gliding speed of traditional UGs is usually very slow, and a thruster is sometimes added to improve the speed. The UG equipped with a thruster is usually called the hybrid-driven underwater glider (HUG). When the thruster is working, the HUG has higher velocity, but the wing produces much drag force. So, a new design scheme, equipping a foldable wing module on the top of the HUG, is proposed to reduce the drag force in this paper. There is no doubt that the change of wing structure will affect the gliding motion performance of the glider. And some scholars have studied these effects. Shankar and Vijayakumar (2020) studied the effect of wing position on the hydrodynamic characteristics of a UG by computational fluid dynamics (CFD) methodology. The results show that positioning the wing at the farthest point aft improves the performance of the glider but the increase is very small and visible at higher attack angle. Javaid (2017) studied the effect of wing form on the hydrodynamic characteristics of a UG. The results show that the glider with rectangle wings has higher lift force and drag force than the glider with tapered wings due to a larger wetted area. Zhang (2014) developed a prototype of a gliding robotic fish with two types of wings with the same wingspan but different aspect ratios. The results show that the larger wings result in shallower gliding paths but a slower gliding speed compared with the smaller wings. Liu (2014) designed an orthogonal test to study the impact of wings on the movement efficiency and stability of a HUG. The results show that the chord length has the most remarkable effect on the movement efficacy and the sweep angle has the most significant impact on the stability of the HUG.
