Underwater gliders are winged, autonomous underwater vehicles that are broadly applied in physical and biological oceanography. The wings have an important impact on the hydrodynamic performance of the underwater glider. In this paper, the effect of wing flexibility on hydrodynamic performance of an underwater glider is studied by computational fluid dynamics (CFD) methodology. The results show that the wing deformation will reduce the lift force, drag force and pitch moment of the underwater glider. The larger the Young's modulus of the wing, the smaller the influence of the wing flexibility on the hydrodynamic performance of the underwater glider.
An underwater glider 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 underwater gliders have been developed and broadly applied in physical and biological oceanography, such as Slocum (Webb, 2001), Spray(Sherman, 2001) and Seaglider(Eriksen, 2001).
Underwater gliders move in the horizontal plane through the hydrodynamic force acting on the wings. Therefore, the wings greatly affect the hydrodynamic characteristics of underwater gliders. And some scholars have studied these effects. Fan and Woolsey (2013) studied the effect of a few geometric parameters on the steady wings-level gliding and steady spiral motion of a glider. The conclusions include the fact that using smaller wingspans can attain to higher speed but smaller lift-drag ratio. Positioning the wings father aft can improve the stable of the glider's longitudinal dynamics. Liu (2014) studied the impact of wing layout on the movement efficiency and stability of a hybrid underwater glider by orthogonal test. The results show that the chord length is the most important influence factor to the lift-drag ratio and the sweep angle has the most significant impact on the stability of the glider. Javaid (2017) investigated the effect of two different wing forms on the hydrodynamic performance by experimental and numerical methods. The results show that the glider with the rectangular wings has 15% more drag force and 17% more lift force than the glider with tapered wings when the pitch angle is 12°. Shankar and Vijayakumar (2020) discussed the effect of wing position on the glider's lift and drag characteristics by computational fluid dynamics (CFD) methodology. The study brings out that positioning the wings at the farthest point aft improves the hydrodynamic performance of the glider. The lift-drag ratio of the glider with wing position farther aft is 6% higher than that of the glider with the position at the forward of the glider when the attack angle is ±8°.
