Numerical Simulation Study And Trial On A Large Ship Undocking

Ship undocking are the necessary processes in ship repairing or shipbuilding. Now the traditional empirical method is used in ship undocking at both home and abroad. The ship undocking plan and the configuration of tugs are decided after the ship undocking environmental loads are estimated. Starting from studying various environmental loads during the ship undocking process, an environmental loads calculation model and the environmental loads testing methods are established in this dissertation utilizing the orthogonal design theory. This dissertation also analyzes the impacts of the environmental loads at various ship undocking conditions. Utilizing the current optimization technique and fuzzy evaluation method, this dissertation creatively studies the tug configuration mechanism and the ship motion simulation forecasting during the ship undocking process. A special topic regarding the effect of the breakwater during the ship undocking process is also studied. The above study reduces the blindness of ship undocking and provides the theoretical foundation and practical guidance for the ship undocking operation.Firstly, the mathematical models on a large ship undocking numerical simulation forecasting are studied and tested systematically. The ship hydrodynamic forces, the wind, wave and current forces , the shallow water effect and the wall effect are studied in detail. The mathematical model for solving the problem is established.Secondly, a ship undocking process environmental forces testing plan is made by using the orthogonal design theory. Measuring the environmental forces with different wind, wave and current combination from 0?to 90?and analyzing and processing the data are finished by using the analysis of variance method. Comparing the experimental results with the results calculated using the OCIMF method, the reliability of using the OCIMF method is testified.Thirdly, the basic configuration plan of a ship undocking assisted by different number of tugs is given. The relationships among the gyroidal moment, gyroidal time and drag forces of tugs in the process of ship undocking are analyzed. The margin of the tugs' towing forces during the ship undocking and turning process is studied.Fourthly, this dissertation studies the optimization of the tug configuration based on the genetic algorithms (GA) during the ship undocking process. The optimization results show that the genetic algorithm is stable and reliable. The tug configuration and the well utilization of the tugs are researched by using the multi-objective optimization genetic algorithm in order to guarantee safety during the ship undocking process. An inverse solution is achieved by using the multi-objective optimization genetic algorithm regarding the tugboats adequacy and configuration and the safety margin in the undocking process when the quantity and power of the rented tugs are known.Fifthly, extensive study and testing are carried out regarding the ship undocking process simulation forecasting on some typical ship types, e. g. 175000 DWT bulk carrier and 300000 DWT oil tanker. The simulation of ship undocking is realized by establishing the ship undocking mathematical model, finding the numerical solution of the differential equation and establishing the calculation model and solution method regarding the towing forces in the undocking process. Simulation forecasting is conducted regarding three typical ship types. The research results are applied in the undocking of the 175000 DWT bulk carrier and the "PANYU" FPSO in Shanghai Waigaoqiao Shipbuilding Co. Ltd..Finally, analysis and research are conducted regarding the ship current load changes after a breakwater is added in the dock in Shanghai Waigaoqiao Shipbuilding Co., Ltd.In a word, by analyzing various loads and the calculation method during the ship undocking process, the simulation model of the ship undocking is established, the simulation forecasting regarding the ship undocking process is carried out and the tug configuration is optimized. The problem of...