Peng Wang

Autonomous underwater glider fleets are increasingly deployed to observe mesoscale eddies, yet a methodology for evaluating observation quality under uncertainty remains lacking. This paper presents SCOPE, a framework integrating uncertainty propagation, multi-dimensional assessment, and objective metric selection. A 27-metric evaluation system spanning seven quality categories is constructed; an Adaptive Core Metric Selection (ACMS) algorithm compresses these to a compact core subset. Two-stage sensitivity analysis identifies the velocity ratio as the dominant parameter with a non-monotonic effect. The optimal velocity ratio decreases with eddy intensity in both an analytical model (0.58 to 0.47) and four real HYCOM eddies (2.35 to 0.35). ACMS converges on all four real eddies, and parameter rankings are consistent across environments. An ablation experiment in the analytical model validates the effectiveness of the two sensitivity-derived design rules (25% and 45.8%) gap closure and reveals their non-additive interaction. SCOPE offers a framework and diagnostic workflow for uncertainty-aware evaluation of autonomous ocean observation systems.

Autonomous underwater glider fleets are increasingly deployed to observe mesoscale eddies, yet a methodology for evaluating observation quality under uncertainty remains lacking. This paper presents SCOPE, a framework integrating uncertainty propagation, multi-dimensional assessment, and objective metric selection. A 27-metric evaluation system spanning seven quality categories is constructed; an Adaptive Core Metric Selection (ACMS) algorithm compresses these to a compact core subset. Two-stage sensitivity analysis identifies the velocity ratio as the dominant parameter with a non-monotonic effect. The optimal velocity ratio decreases with eddy intensity in both an analytical model (0.58 to 0.47) and four real HYCOM eddies (2.35 to 0.35). ACMS converges on all four real eddies, and parameter rankings are consistent across environments. An ablation experiment in the analytical model validates the effectiveness of the two sensitivity-derived design rules (25% and 45.8%) gap closure and reveals their non-additive interaction. SCOPE offers a framework and diagnostic workflow for uncertainty-aware evaluation of autonomous ocean observation systems.

Currently, underwater vehicles are playing an increasingly important role in ocean observation, and rapid vehicle design is required for the increasingly diversified missions. Hydrodynamic shape is a vital discipline in underwater vehicle design, which consists of many mutually coupled design parameters. In this article, a machine learning-enhanced rapid design method is proposed to design the hydrodynamic shapes for the establishment of underwater vehicle pedigrees. The framework of the method is introduced, and a case study is detailed for the shape design of the underwater glider (UG). The shape of UG is optimized following various criteria to validate the feasibility of replacing the traditional computational fluid dynamics method with the machine learning method. Finally, a circulating water channel test is performed to validate the accuracy of the hydrodynamic data, while sea trial data are adopted to verify the correctness of the dynamic model for motion performance evaluation. The design method proposed can largely shorten the design cycle of underwater vehicles, and the broad design space explored in the case study helps build the hydrodynamic database of traditional UG hulls, thereby promoting industrialization.

The pressure hull is the main buoyancy component of underwater gliders (UGs), and its volume change during upward and downward gliding has a great influence on the motion performance and endurance of UGs. To improve the buoyancy compensation ability of the pressure hull, this study designs a rigid-flexible composite pressure hull with a sandwich structure (simplified as sandwich hull), which consists of a rigid outer layer, a flexible middle layer, and a rigid inner layer. The differential equations for axial and radial deflections of the sandwich hull under external pressure are deduced based on the thin shell theory, and the distribution of deformation and pressure on the three layers is obtained. The objective function for the buoyancy change of the sandwich hull is established, and the hull parameters are optimized with the genetic algorithm and then verified by the pressure test. The optimized sandwich hull shows better buoyancy compensation performance than the traditional rigid one, with more than 19% reduction in the buoyancy change per unit volume. The designed sandwich hull is applied to the theoretical model of a “PETREL” UG to replace the traditional rigid hull, and the calculation results show that no other buoyancy compensation and attitude adjustment are required during the gliding process down to 1000 m.

Underwater gliders (UGs) integrating multiple sensors have become crucial platforms for marine observation and detection. When subjected to fluid forces, UGs equipped with acoustic payloads at wingtips exhibit reduced measurement fidelity due to the substantial hydrodynamic noise. This study systematically explores the generation mechanisms of hydrodynamic noise in glider wings by coupling numerical and experimental validation. First, the bidirectional fluid–structure interaction method is implemented for numerical simulation, yielding time–history structural dynamics and transient flow field characteristics around the wing. Subsequently, an improved Lighthill's acoustic analogy is developed to transform flow field characteristics into noise sources, enabling numerical analysis of hydrodynamic noise. Additionally, the dominant hydrodynamic noise sources are identified through integrated analysis of flow field characteristics and wet modal simulation, with their sound pressure level primarily concentrated in a low-frequency band (0–200 Hz). The results indicate that peak frequencies (4, 11, 21, 40, 53, and 61 Hz) of flow noise are mainly attributed to flow separation near the leading edge and its associated vortex structures, while peak frequencies (89, 109, and 129 Hz) of flow-excited noise are predominantly governed by wing modal responses. Finally, the modal testing and sea trial of the glider demonstrate that discrepancies between experimental and simulation results are within 10%, confirming the origin of peak-frequency hydrodynamic noise. These findings provide critical insights for optimizing glider wing designs to suppress hydrodynamic noise.

The buoyancy-driven underwater glider serves as a highly efficient tool for achieving ocean-wide, long-term, and continuous fine-scale observations. However, the performance of underwater gliders in the gliding range and speed is significantly influenced by biological attachments. To investigate potential solutions for this issue, this study explores the drag reduction mechanism of the Petrel-L underwater glider's main body based on the biomimetic superhydrophobic surface (BSHS). The flow field surrounding the underwater glider is analyzed through particle image velocimetry, and mechanical measurements are obtained with force balance techniques. The drag reduction effect of the BSHS with/without biological attachments is accurately determined through force balance analysis. Additionally, the impact mechanism of the boundary layer on Petrel-L with/without biological attachments is investigated with a range of analytical techniques, including proper orthogonal decomposition, conditional phase averaging, finite-time Lyapunov exponent, and quadrant analysis. At an angle of attack (AOA) of 3°, the BSHS realizes a drag reduction of approximately 15.2% when there are no biological attachments. When biological attachments are introduced, the flow drag of the underwater glider increases significantly, but BSHS achieves a drag reduction of about 16.8%. The drag reduction ability of BSHS is mainly reflected in its reduction of the streamwise fluctuation velocity within the boundary layer and achieves relaminarization of the boundary layer under the influence of AOA. These findings suggest that the BSHS retains its remarkable drag reduction capability for the underwater glider, even in the presence of adverse AOA and biological attachments. The current study demonstrates the immense potential of BSHS in the realm of underwater vehicles and offers theoretical and empirical support for future investigations into hydrodynamic performance optimization and passive drag reduction technologies for underwater vehicles.

Quickly and long-distance deployable air-dropped underwater gliders (ADUGs) have significantly improved the efficiency of ocean observations. However, the ADUG inevitably suffers from a huge impact during the water entry, which exerts a great influence on the success rate of deployment. In this paper, a three-dimensional numerical model of an ADUG is established through fluid–solid coupling of smoothed particle hydrodynamics and finite element method. Numerical simulation is performed to analyze the impact characteristics of the ADUG when entering hydrostatic water under different initial water entry conditions and the bouncing characteristics after the entry. The dynamic design analysis method is adopted to investigate the structural response characteristics of the ADUG during vertical water entry based on impact response spectra and modal analysis. A hydrostatic water tank experiment is performed with a scaled-down model of the AUDG, and the maximum error of the peak acceleration ap between the experimental and simulation results is 7.61%, proving good engineering applicability of our approach. The analysis results can be used to guide the structural design and deployment planning of ADUGs, which also provide a theoretical reference for the water entry research of other air-droppable equipment with complex shapes and structures.