Optimization Design Of Cargo Hold Structure Of V-type Non Ballast Water Tanker

With people’s attention to green ships,the treatment of ship ballast water has become a hot spot of ship green research.Although the current ballast water treatment methods have their own advantages,but there are some problems,which can not completely eliminate the impact of ballast water.In order to find a new way of ballast water treatment,the non ballast water vessel came into being.At present,there are three mature schemes.The V-shaped hull design can meet the design requirements from the test results,and the performance is better than the traditional hull,which is a scheme to solve the problem of ballast water.Due to the lack of relevant specifications for V-type ships,most of the structural types of V-type ships refer to the parent ship,and the structural design also refers to the parent ship,which is not completely suitable for the actual situation of V-type ships.Modern structural optimization methods are used to optimize the design,so as to obtain a more reasonable structural type,improve the hull structural performance,and achieve the purpose of more energy saving,material reduction and safety.In view of this,this thesis carries out topology optimization design and size optimization design for V-type non ballast water tanker from two aspects of reducing the weight of cargo hold structure and lifting strength.Using the parent ship transformation method to determine the initial structure,using topology optimization to determine the strong frame structure,using sensitivity analysis to screen variables-test design to generate sample points-establish an approximate model-using optimization algorithm to optimize the size.It can quickly and effectively realize the structural optimization design of V-shaped ship,reduce the number of simulation calculation in hull structure optimization,shorten the R & D cycle and reduce the R & D cost.The main research contents are as follows:Firstly,the finite element models of 1/2+1+1/2 cabin in cargo hold area of parent ship and V-type non ballast water tanker are established,the finite element mesh is divided,the material properties are set,the model coordinate system and boundary conditions are selected,and the load calculation and working conditions are selected according to the code.Through the finite element calculation,it is found that there are some differences in the structural characteristics of the two ship types,and the new method is feasible There is a certain degree of strength redundancy in ship structure,and there is a lot of optimization space,which lays the foundation for the next structural optimization design.Secondly,the topology optimization theory is used to optimize the V-type non ballast water oil tanker cargo hold strong frame structure,and the appropriate optimization design area is selected.Taking the sectional weight as the constraint condition,and considering the characteristics of the actual production and construction process,the minimum flexibility value(i.e.the maximum stiffness)is taken as the objective function to establish the topology optimization mathematical model,and the optimization design area is analyzed and determined The influence of different initial thickness on the optimal design.After topology optimization,the strong frame structure of the ship is determined,so that the structure can be further optimized and improved.Finally,the radial basis function(RBF)surrogate model and a variety of optimization algorithms are combined to optimize the size design.The components that have a greater impact on stiffness and weight are selected as design variables by sensitivity analysis.The optimal Latin hypercube is used to select the sample points to construct the RBF neural network surrogate model,and then a variety of optimization algorithms are used to optimize the design.Taking the minimum cabin weight as the objective function,the single objective size optimization design is carried out.After optimization,the cabin weight is reduced by6.92%.The multi-objective optimization design is carried out with the minimum cabin weight and the maximum rigidity.The optimal solution is calculated by entropy method.The cabin weight is reduced by 1.15%,and the cabin rigidity is increased by 4.3%.