Design of a wave-shaped towing cable for stable, low-drag acoustic monitoring in wave glider systems

As wave-powered unmanned surface vehicles, wave gliders offer an effective platform for persistent marine acoustic monitoring. However, the deployment of deep-towed acoustic systems from these platforms is impeded by challenges such as hydrodynamic drag, motion instability, and flow-induced noise, particularly in elevated sea states. A novel acoustic towing system featuring a wave-shaped cable, with strategically distributed float-sinker pairs, is presented here. Its performance is optimised through parametric tuning of the wave number, wavelength, and amplitude to mitigate drag and suppress vortex-induced vibrations. To understand the complex dynamics of the system, a comprehensive hydrodynamic model combining Euler-Lagrange dynamics with computational fluid dynamics was developed. This integrated framework facilitated a systematic investigation of the critical cable parameters for effective drag reduction and suppression of vortex-induced vibrations. Simulations revealed that low-frequency disturbances induced larger attitude fluctuations in the towed body than their high-frequency counterparts. Furthermore, the vibration-damping effectiveness of the cable was found to increase with wave number, albeit at the cost of reduced towing speed. An analysis of the acceleration power spectral density revealed that a critical, speed-dependent trade-off among damping performance, system stability, and hydrodynamic drag governs the optimal float-sinker configuration. At low speeds (≤0.5 m/s), a configuration of 12–14 float-sinker pairs per wavelength yields superior overall performance. At higher speeds (≥1.0 m/s), a sparser configuration offers lower drag but risks resonant amplification, whereas a denser layout ensures stability at the expense of higher drag. This validation was substantiated by the alignment between the dominant response frequency of the towed body with wave excitation and the effective suppression of high-frequency vibrations. Collectively, these findings demonstrate that strategically configured towing cables can significantly enhance the operational performance of wave glider-based acoustic monitoring systems by improving hydrodynamic efficiency and mitigating flow-induced vibrations and their associated noise. The findings of this research provide a robust foundation for future studies of adaptive towing strategies and multi-body hydrodynamic interactions in marine environments.