Shape Design And Optimization Of Autonomous Underwater Vehicle With The Capability Of Landing On The Seafloor

AUV (Autonomous Underwater Vehicle) with the capability of landing on the seafloor is one kind of unmanned and untethered underwater vehicle which can fulfill oceanographic environment survey,and it has become an intense area of oceanic research because of their emerging applications in oceanographic survey. However, long-term marine environment measuring is impractical for available AUVs because the energy storage is limited. It is useful to develop the variable buoyancy AUV with the capacity of landing on the seafloor and bottom-sitting for an extended measuring period. Because of more attached bodies, the new AUV developed in the thesis is more complicated than conventional AUVs in shape and construction. In this thesis, a low cost modular AUV with the capacity of landing is developed and optimized to reduce drag and get effective maneuverability.The main contributions of the thesis are summarized as follows:1. The hull form and structure of the AUV with the capacity of landing are designed in this thesis, there are one main cabin and two ballasts for achieving main functions, and four rudders are used as control plane, and a thruster is laid at the aft part of the AUV. The main cabin and two ballasts are connected by four support frames.2. Applying Computational Fluid Dynamics (CFD) method, the hull form of the main cabin is optimized. One kind of typical hull form is chosen to study the drag characteristic of the AUV with low speed and the results are summarized as follows:The drag coefficient of the AUV is varied with its speed greatly,so it is very important to emphasize the dynamic similarity; The change of the curvature along streamline shape of the head and tail should be kept small to reduce drag; the longer the tail is,the less drag is; When the volume is kept constant, the bigger slenderness ratio is, the less drag is. Based on these conclusions,the cabin is optimized to reduce drag.3. In this thesis,thickness of the rudders are changed smaller than conventional design, and configuration of support frame are modified simple. As to the shape of support frame and GPS backstay are designed to keep a swept–back angle to reduce drag. The installed position of CTD sensor is also optimized. The result of CFD simulating indicates that the purpose of reducing drag has been achieved and the drag of the optimized AUV is decreased by 37 percent.