Research On The Hydrodynamic Performance And Parametric Optimization Of A Full Ocean Depth Human Occupied Vehicle

The area with a water depth above 6,500 meters is defined as “Hadal Zone” by the international marine scientific community.Hadal science which consists of geology,biology,and ecology is shortened from the science of the ocean that specializes in the study of the hadal zone.The research of hadal science relies highly on the deepsea equipment,which can operate and take samples in the hadal areas.In such circumstance,the full ocean depth(FOD)submersible with deeper descending and longer operating times will play an increasingly important role in the scientific research in hadal zones.In the hydrodynamic design of a FOD human occupied vehicle(HOV),some key points will be discussed.How to achieve rapid descending from the water surface to the ocean floor through motion optimization.To reduce resistance and energy consumption through molded lines optimization,a long-term underwater operable duration will be ensured.Accordingly,the hydrodynamic discipline,which can solve a series of hydrodynamic problems,plays an increasingly important role in the design of deepsea submersibles.The submersible's economical,practical and safety can be influenced on pros and cons of hydrodynamic performance.In this dissertation,the “Rainbowfish” FOD-HOV,which is being developed by Shanghai Ocean University HAST,is chosen as research object.To solve the above problems,this dissertation mainly carries out the following work:(1)This dissertation summarizes the existing domestic and international FOD unmanned and manned submersibles,focusing on the functions and performance of FOD submersibles.Starting from hydrodynamic performance research methods,three different methods of theoretical analysis,experimental research,and computationalfluid dynamics are outlined.At the same time,the main contents of the hydrodynamic performance of the submersible are introduced,including resistance calculation,molded lines optimization design,and speed and attitude simulation of the descending and ascending process,and a summary of each part.(2)Computational fluid dynamics methods are used to carry out numerical calculations under the conditions of advance motion and vertical descending/ascending.In order to establish an accurate finite element model,the sensitivity studies of factors such as calculation domain scale and mesh size,as well as the applicability of different turbulence models in the calculation of resistance to direct navigation and descending/ascending,were conducted,and a suitable turbulence model was selected.The validity of the numerical model is verified by comparing with the existing experimental data.The numerical grid model and turbulence model under different working conditions were obtained.Based on the established numerical calculation model,CFD simulations were performed for different conditions of forward movement and descending/ascending in several pitch angles,and the resistance and effective power at different speeds were obtained.The flow field performance under different conditions was analyzed by the flow field contours.(3)This dissertation studies the resistance performance of the submersible,and obtains a low-resistance shape scheme by optimizing the molded lines.Starting from the flow field contours of the forward working condition,the resistance performance of the submersible was studied,and the bow molded lines was used as the optimization target.The CATIA-ICEM CFD-Fluent integrated optimization platform was built in Isight.The DOE,kriging approximation model and optimization algorithm are combined through optimization analysis,obtained the optimized submersible shape model,which reduced the moving resistance.(4)In this dissertation,the unpowered descending and ascending movements of the submersible are studied through different research methods,and the performance of the unpowered descending and ascending movements of the submersible is obtained.The following submerged motions are used as the calculation conditions.Without considering the rudder force,the submerged motions are regarded as a uniform linear motion in a two-dimensional plane and a two-dimensional plane motion withacceleration and angular velocity.The situation is analyzed separately.When viewed as a linear motion at a constant speed,the three different placement positions of the ballast iron are analyzed.By establishing the equation of motion and using Matlab software to calculate and analyze each operating condition,the descending time is determined by the weight of the ballast iron.The change relationship of the parameters intuitively expresses the influence of different parameters on the descending.When it is considered as a movement with acceleration and angular velocity,the influence of seawater density on the movement is taken into account.Simulink module in Matlab is used to build an unpowered descending motion model and simulate it.The results of the descending motion trajectory and speed curve are obtained.Obtained dive performance.The specific research significance is as follows:(1)A set of numerical calculation models with good applicability are established in this dissertation,which can not only lay a good foundation for the design of manned submersibles,but also provide a certain reference for other underwater objects to perform fluid simulation.(2)This dissertation comprehensively performs numerical simulations on various conditions of the submersible forward and backward and multi-angle descending and ascending.The resistance and effective power at multiple speeds are obtained,which can provide a theoretical basis for the subsequent configuration of the propulsion system of the submersible.(3)The three-dimensional model of the submersible obtained in this dissertation not only improves the resistance performance,but also can help the design of the submersible to a certain extent.The optimization process designed in this dissertation can also provide certain ideas and methods for engineers to optimize the underwater equipment profile and structure.(4)This dissertation comprehensively analyzes the unpowered descending movement of the submersible,and provides theoretical support for the subsequent submersible design of the submersible.