Research on Sailing Efficiency of Hybrid-Driven Underwater Glider at Zero Angle of Attack

The sailing efficiency of an underwater glider, an important type of marine environment detection and data collection equipment, directly affects its range and duration. The zero-angle-of-attack gliding can be achieved by adjusting the wing installation angle to minimize the drag and improve the sailing efficiency, and thus further improving performance of the glider. This paper first presents the dynamic characteristics of a hybrid-driven underwater glider with a certain wing installation angle when it is sailing at zero angle of attack in buoyancy-driven mode and hybrid-driven mode. In buoyancy-driven mode, with a given wing installation angle, the glider can achieve zero-angle-of-attack gliding only at a specific glide angle. In hybrid-driven mode, due to the use of a propulsion system, the specific glide angle that allows the zero-angle-of-attack gliding in buoyancy-driven mode is expanded to a glide angle range bounded by zero degrees. Then, the energy consumption per meter is introduced as an indicator of sailing efficiency, and the effects of glide angle and wing installation angle on sailing efficiency of the zero-angle-of-attack glider in two driving modes are studied under the conditions of given net buoyancy and given speed, respectively. Accordingly, the optimal wing installation angle for maximizing the sailing efficiency is proposed. Theoretical analysis shows that the sailing efficiency of a zero-angle-of-attack glider can be higher than that of a traditional glider. Considering the requirements of different measurement tasks, a higher sailing efficiency can be achieved by setting reasonable parameters and selecting the appropriate driving mode.

Across-shore Propagation of Subthermocline Eddies in the California Current System

Though subthermocline eddies (STEs) have often been observed in the world oceans, characteristics of STEs such as their patterns of generation and propagation are less understood. Here, the across-shore propagation of STEs in the California Current System (CCS) is observed and described using 13 years of sustained coastal glider measurements on three glider transect lines off central and southern California as part of the California Underwater Glider Network (CUGN). The across-shore propagation speed of anticyclonic STEs is estimated as 1.35-1.49 ± 0.33 cm s−1 over the three transects, Line 66.7, Line 80.0, and Line 90.0, close to the westward long first baroclinic Rossby wave speed in the region. Anticyclonic STEs are found with high salinity, high temperature, and low dissolved oxygen anomalies in their cores, consistent with transporting California Undercurrent water from the coast to offshore. Comparisons to satellite sea-level anomaly indicate that STEs are only weakly correlated to a sea surface height expression. The observations suggest that STEs are important for the salt balance and mixing of water masses across-shore in the CCS.

Design and analysis of low-cost underwater glider for shallow water

This paper aims to design a low-cost underwater glider to operate in shallow water. The proposed design was developed by manufacturing engineering software. Analysis of the hull using manufacturing engineering software and 3D computer-aided design (CAD). The analysis of hydrodynamics using computational fluid dynamics (CFD). This glider was designed to operate in shallow water, coastal, lake and river for a maximum depth of 10 m and a maximum speed of current 12,96 km/h, or 3,6 m/s. To reduce and minimize the cost to manufacture this underwater glider, the mechanics, electrical, electronics, and power source were using common tools on the market, not on demand. Based on numerical model, the hull pressure had 30,127 psi or 0,2077162 MPa for maximum depth 10 m and max speed 12,96 km/h. Maximum pressure occurs on the nose and behind the wings. This unmanned vehicle was designed to be in 9 compartments. The first compartment and 8th compartment are used for ballast tanks. The others for: mechanics of ballast system, altimeter and attitude controller, payload, battery pack, main controller part, propulsion system, and propulsor.