The Comprehensive Optimization Research Of The Ship Hydrodynamic Performance Based On MDO

The traditional ship design mostly adopts the parent ship transformation method, only the pursuit of some main performance targets to meet the requirements.Even if it carried out optimization design, but also for some indicators of individual disciplines, without taking account of harmonious balance between the various disciplines performance and making the comprehensive performance of design ship system to achieve optimal, which severely limits the improvement of ship design quality. Therefore, the current ship design urgently need a new design theory and method as guide.With the development and maturity of the modern product design methodology and the progress of computer related technology, there are some new methods and patterns in the design of the complex engineering products system. Multidisciplinary design optimization method, which originated in the aerospace and aviation field, is a typical example of the advanced design methodology. This method can make full use of the synergistic effect produced by the interaction of various subjects to obtain the global optimal solution of the system. And it can shorten the design cycle by implementing parallel design so that developed products can be more competitive.At present, the basic theory of this method has got a relatively mature development. But it is very difficult to apply the method to the project as complex as ship engineering. The major reason is a lot of key issues, such as the system modeling technology, parametric main model, the mechanism of subject view model and so on, of ship engineering have not been effectively solved. To study and solve the key issues will be very helpful in the promotion of implementation the multidisciplinary design optimization methods to the ship field.Based on the above analysis, this paper mainly introduces the key issues around the ship itself. This thesis mainly around the research of the key techniques about the multidisciplinary design optimization of the ship shape line of the hydrodynamic performance in order to reduce the complexity of the problem and narrow research scope. Aimed to provide ideals of how to effectively implement MDO into ship field, this paper mainly discussed the characteristics of the multidisciplinary design optimization and model of design process. Based on the above works, we studied the basic theories which are needed to be solved in process of the system from the ship shape line hydrodynamic performance comprehensive optimization problem. Finally we built the ship shape line multidisciplinary design optimization platform. The main research contents include the following six aspects:1. Ship variable-complexity evolutionary design processShip design is a complex engineering problem with multidisciplinary, multi-objective, variables and constraints. The traditional spiral design method is an important model in the ship design process history, which has been approved by the majority of designers.But the traditional spiral design more explains the design steps and is not perfect in the description about design process itself. On the basis of the analysis of ship design features, it summarizes the shortcomings of the traditional design process model and develops the ship design process model based on MDO.For the good implementation of multidisciplinary design optimization methods, it analyzed the essence of the ship system design and developed into a variable-complexity evolutionary design pattern combining the evolutionary design ideas with variable -complexity modeling method.2. Hull line parametric main modelingIn the Ship multidisciplinary design optimization process, various disciplines need carry out the corresponding simulation analysis.In order to ensure the uniqueness of the data source required by the various disciplines analysis,we must establish the main ship model, each subject optimization is all around the main model.With the hull lines main modelling as the exact goal, putting forward the comprehensive optimization for the realization of ship hydrodynamic performance, it must establish the main model of hull lines through the parametric technology deeply study the hull lines parametric modeling principle, compare and analyze the existing parametric modeling methods, and propose ship hull surface modified fusion technology based on NURBS.3. The view modeling of Ship hydrodynamic performance analysisAround the hull lines main model, discipline view model,which various disciplines need, is not different, so it must be based on the same main model, for the hydrodynamic performance of different disciplines to provide the corresponding discipline view model.This is the key to realize automatic optimization.To achieve this goal, it proposed an idea of multidisciplinary view modeling based on the main model for the hydrodynamic performance, in the way of implementation mainly through parsing and conversion of the main model (IGES) file, developed model generator, and provided respectively for resistance and seakeeping performance analysis the corresponding discipline view model.4. Comprehensive optimization mathematical model establishment and system reconstructionTo realize the ship hydrodynamic performance comprehensive optimization, it must set up optimization mathematical model according to the specific optimization problem.It respectively expounds the selection and determination methods of optimize variables, optimize objectives and constraint condition. According to the solution of the optimization mathematical model, it analyzes the deficiency of the existing gradient algorithms and put forward the Pareto method of multi-objective optimization.It analyzes the structure of ship hydrodynamic performance optimization system and must reconstruct the optimization system to improve efficiency of optimization, By using the IDF model, it proposes system reconstruction method based on Pareto method and analyzes optimization process after the system reconstruction.5. Platform development and examplesFor supporting ship variable-complexity design mode, we research multidisciplinary design optimization in order to provide convenient environment for the engineering design people. Emphasizing on the basis of ship hydrodynamic performance comprehensive optimization process platform, it study data integration and process integration method in the process of platform implement and based on it, develops the hull lines multidisciplinary design optimization platform.Finally, they are verified by some ship optimization examples and the result shows that the software platform has engineering practical value.6. Improve Ship form optimization efficiencyIn order to improve the efficiency of the optimization of ship types, combined with the ship hull line multidisciplinary design optimization platform, it puts forward the man-machine combined with thought. It expounds that before starting the linear optimization, we should use experts experience to build ship type library and based on expert experience to set the optimal solution. To obtain the global optimal solution, it discusses the deficiencies of the existing optimization algorithm, put forward the ideas of the hybrid optimization algorithm and the numerical example validation.