Maneuverability Analysis Of An Autonomous Underwater Vehicle With Large-Scale Appendages And Interaction Between Two Bodies

Along with the development of marine exploration and research,as special operation platforms in the marine field,small autonomous underwater vehicles(AUV)will undertake more underwater tasks.Small autonomous underwater vehicles with appendages in large scale need to move neatly in the ocean environment for some specific tasks.After working several hours underwater,they need to navigate towards the underwater space station or carrying platform for energy replenishment and data exchange.Thus they are usually disturbed by the complex and trouble flow field around the underwater space station or carrying platform.It is necessary to understand the hydrodynamic performance and maneuverability of a small autonomous underwater vehicle with specific appendages or in the complex flow field in order to control its navigation and work status better.The hydrodynamic performance and maneuverability of a small autonomous underwater vehicle with and without large-scale appendages were researched and analyzed by using the methods of computational fluid dynamics(CFD),experiment and computational motion simulation.The hydrodynamic interaction characteristics were also calculated numerically in the recovery process of a small autonomous underwater vehicle to a submarine.The main research contents are as followed:Firstly,based on CFD technology,the hydrodynamic performance of a small autonomous underwater vehicle with and without large-scale appendages were predicted with multi-block structured grid and modular grid,which includes resistance,thrust,interaction performance between the body and the propeller,performance of rudders used in the body,maneuvering hydrodynamic performance and hydrodynamic performance of a small autonomous underwater vehicle closing to the water surface.Parts of hydrodynamic performance were compared and validated with experimental results.Secondly,maneuvering tests of a small autonomous underwater vehicle with and without large-scale appendages were conducted in the circulating water channel and the general deepwater pool,including constrained model test and full-scaled test of a small autonomous underwater vehicle.The hydrodynamic performance and maneuverability of a small autonomous underwater vehicle with and without appendages were predicted and evaluated.The usability and accuracy of the numerical calculation method and the computational motion simulation were validated.Thirdly,the nonlinear mathematical model of a small autonomous underwater vehicle in the spatial motion was erected.The hydrodynamic loads acting on a small autonomous underwater vehicle were analyzed.Combining modelling hydrodynamic experiments and numerical calculation results,a motion simulation system was established and a series of maneuvering motion simulation tests of the small autonomous underwater vehicle with and without large-scale appendages were carried out.The maneuverability of the small autonomous underwater vehicle with and without large-scale appendages were compared and analyzed,and the simulation results were verified through test results.Meanwhile,the motion stability of the small autonomous underwater vehicle was analyzed by using hydrodynamic coefficients.Finally,the flow field around a submarine was calculated by RANS equations method in order to select the recovery location of a small autonomous underwater vehicle.The hydrodynamic interaction performance between a 2D or 3D small autonomous underwater vehicle and a submarine was numerically simulated in the retrieving process with the non conformal grid algorithm.The hydrodynamic characteristics of a small autonomous underwater vehicle in the disturbed flow field were investigated in a variety of positions relative to the submarine.Combined with dynamic grid technique,hydrodynamic interaction performance was numerically predicted when a small autonomous underwater vehicle was moved to a submarine in a given path.The research results show that,the small autonomous underwater vehicle with and without large-scale appendages has good maneuverability;the numerical calculation method has certain accuracy and feasibility in predicting the hydrodynamic performance;the maneuverability is predicted accurately using the computational motion simulation method;and it is more reasonable to adopt the numerical calculation method to solve the hydrodynamic interaction problem which often occurs between a small autonomous underwater vehicle and a submarine.The research results would lay a foundation for the theoretical analysis on the motion control of the small autonomous underwater vehicle,in order to develop a more effective control strategy and achieve a more accurate motion control.