Sea Technology

DEC 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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Page 21 of 83

Stability of depth and attitude in the vertical plane with a speed of 3 knots. signed with a slender asymmetric body, with a maximum diameter of 800 millimeters and a length of 7.8 meters. For the contour design, the Granville streamline was adopted, and CFD Fluent software was used to obtain hydrodynamic derivatives and sailing resistance by simulating the fow feld of the vehicle. Through dynamic simulation, the contour of the AUV was optimized to minimize resistance. Optimization resulted in a drag coeffcient of 0.31, and the diameter of the turning circle is predicted to be 35 meters at a 15 degree rudder angle. According to the value of drag force at various working speeds, the ducted propeller and propulsion motor were designed and selected. Further, the power consumption of the vehicle should also be determined. Consulting the requirement of voyage and endurance, the battery capacity is determined as 36 kilowatts. A simplifed open, free-food structure was adapted to the vehicle, with most of the equipment submersed in water to avoid the problem of buoyancy defciency raised by a massive pressure-resistant cabin. The total weight of the AUV is 2,200 kilograms, and all the payload sensors, electronic components, vectored thruster and buoyancy materials are fxed on the main frame. The frame consists of two longitudinal beams, fve cross beams and fve keels. The longitudinal beams are made of stainless steel with a length of 5.8 meters. There are fve cross beams between the longitudinal beams, which are used to lift the vehicle and reinforce the frame structure. Five keels are also fxed along the beams to sustain the glass-reinforced plastic hull. In the process of general design and optimization of the vehicle, strength and rigidity of the frame were verifed by fnite element analysis to make certain that it could fulfll the requirements of practical sailing and lifting operations. When performing an underwater surveying task, the AUV should maintain a constant altitude to acquire bathymetry data more accurately. In order to optimize the maneuverability, especially at a low speed of less than 2.5 knots, a 2-degree-of-freedom vectored thruster was used, which can alter the direction of thrust force with two actuating motors, while the conventional control plane can only present much smaller hydrodynamic force for the attitude control of the AUV, especially at low speed. Enough stern force can in our element Serving the world of Hydrography & Oceanography • Tide Gauges • Sound Velocity • Current Meters • CTD & Multi-Parameter in our element 22 st / December 2013 • Echo Sounders & Bathymetry • Wave Recorders • Telemetry Instruments • Ocean Engineering Tel: +44 (0) 1803 869292

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