Hydrodynamic Performance Enhancement of Unmanned Underwater Gliders with Soft Robotic Morphing Wings for Agility Improvement

TL;DR

This paper investigates hydrodynamic performance gains from soft morphing wings on buoyancy-driven UUV gliders. By structurally modeling a soft wing with a Mooney–Rivlin material and validating it against experiments, then performing CFD Validation against established UUV data, the authors quantify how camber morphing affects lift, drag, and overall efficiency. The main result shows up to a $9.75\%$ increase in the lift-to-drag ratio compared with a rigid-wing UUV, with improved static stability and roll authority, supporting longer-range missions and enhanced maneuverability in cluttered or icy environments. The work lays a foundation for future experiments and indicates that soft robotics can meaningfully extend underwater glider capabilities without substantial energy costs.

Abstract

This work assesses the hydrodynamic efficiency of Underwater Unmanned Vehicles (UUVs) equipped with soft morphing wings compared to conventional rigid wings. Unlike rigid wings, deformable counterparts can alter their aerodynamic properties on demand. Improvements in hydrodynamic efficiency extend a UUV's operational range and may determine mission feasibility. Structural and Computational Fluid Dynamics (CFD) simulations were conducted for both a soft morphing wing and a UUV incorporating it. The results show that a UUV employing soft wings achieves 9.75 percent higher overall efficiency than an equivalent vehicle with traditional rigid wings. These findings confirm the potential of soft robotics to enhance underwater vehicle performance, particularly in applications requiring pressure-agnostic operation.

Figures (9)

• Figure 1: Cross-sectional view of the soft morphing wing showing its profile and internal structure for all deformation levels tested in Giordano2024. From top to bottom: 0mL, 30mL, 60mL, 90mL, and 120mL. All profiles shown are the results of the simulations performed for the present work.
• Figure 2: Correlation between the inflation levels of the soft wing Giordano2024 and the isotropic pressure field applied in the simulations to reproduce equivalent deformations. A second-order polynomial fit $P(I) = -0.025I^2 + 0.7273I - 0.1543$ was applied to the four experimental data points, enabling the extrapolation of 3 additional inflation levels (yellow).
• Figure 3: Camber profiles of the soft wing from the experiments performed in Giordano2024, Fig. 5 (solid black lines), and corresponding profiles as an output of the structural simulations performed for the present work (coloured dots).
• Figure 4: Hydrodynamic characterisation of the soft wing at $Re_2 \simeq 9.2e4$ (free-stream velocity $U_2 = [per-mode=symbol]{0.40}{\metre\per\second}$). Solid lines represent the water tunnel measurements, as reported in Giordano2024, while the dotted lines correspond to the force values obtained from the CFD simulations performed for the present work.
• Figure 5: Domain of all CFD simulation performed by the authors and involving an underwater glider. The cylinder represents the UUV and has a total length of $\overline{IJ} = L_{UUV}$. The parallelepiped of vertices A, B, C, D, E, F, G, and H delimits the water volume. $L_a = L_b = L_h = 1.5\cdot L_{UUV}$, $L_f = 5 \cdot L_{UUV}$.