Study On Under-Keel Clearance For Ultra Large-scale Ships Under Multi-Variables Coupled Interaction

With the development of the shipping industry,ships,especially oil tankers,bulk carriers and containers,have the trend of large-scale,specialization and informatization.With the growing number of super large ships,the risk of stranding and collision accidents will increase,which can challenge the development of traffic safety.Among the factors that affect the navigation safety of super large ships,the under keel clearance(UKC)is a hot and difficult issue concerned by domestic and foreign scholars,maritime authorities and port and shipping enterprises.It is practical significance to carry out the research on the UKC of super large ships to ensure ship's navigation safety and reduce or avoid dangerous accidents such as dragging,touching the bottom and grounding.Under the condition of limited navigation resources,it can make full use of loading capacity to avoid the waste navigation resources.It is practical significance to realize the large scale ship and the optimization of shipping efficiency and safety.Taking UKC of super large ship as the research object,the main line is to study the influence mechanism,calculation method,verification application.The analysis of super large ship's UKC are formed by means of coupling analysis of influence mechanism,numerical calculation analysis,scaled model test and full-scale sea trial.The main content and innovation points of this thesis are as follows:First,study on coupling mechanism of influential factors of UKC.Systematically identify the influence factors of UKC,the hierarchical structure model is built.The system dynamics(SD)model is used to analyze the coupling mechanism of the influence factors of three levels of "man-machine-environment" of UKC.Then,the coupling calculation model of ship subsidence and the UKC calculation model under multi-factor coupling are constructed.Second,the calculation and verification of the ship's dynamic subsidence.The technique of measuring and verifying the sinking of super large ship is determined.The methods of numerical pool calculation,scaled model test and full-scale sea trial are applied to carry out the experimental research respectively.The value range of dynamic subsidence of ships under different test methods is obtained.And the reliability of the coupled calculation model of subsidence is verified.Third,the calculation method of dynamic UKC for super large ships,a three-dimensional safety field model for super large ships is built on the basis of the safe speed concept.Based on the theory of hydrodynamic interference,stopping or reversing distance and ship-following theory,the calculation method of safe speed section and dynamic UKC of super large ships are put forward.Last,the method of determining UKC based on statistics analysis.The Gauss mixed model and the expected maximum algorithm method are used to calculate the UKC of the super large ships and the optimal value standard.Taking Caofeidian port as an example,the standard of UKC for the super large ships under different tonnage and different loading rate is put forward.The thesis systematically carries out the study of coupling mechanism,dynamic UKC,test verification,statistics and other aspects of the UKC of super large ships.Taking Bohai Sea as an example,a case study was carried out.The result shows that the calculation method of UKC proposed in this thesis is in good agreement with the actual situation.The identification of influential factors and coupling qualitative and quantitative analysis of UKC can fully demonstrate the coupling relationship among the elements.The three-dimensional safety field model of the super large ship can fully reflect ship's particularity.The thesis enriches the theory and technology of super large ship's handling and has important guiding significance and application value for the safety guarantee of the super large ships.