Investigation Of YUKUN Vessel's Squat Based On CFD

In the course of sailing,due to the change of flow pattern near the hull,the pressure distribution on the hull surface is not uniform,which causes the heave of the hull.In restricted waters,the rising or falling of the water near the hull will affect the ship's maneuverability.The phenomenon of the hull's sinking and pitching is more obvious than that in infinite waters.In serious cases,it may cause bottom rubbing or grounding,especially in harbor.When traveling,if the influence of squat is not fully considered,there will be a great potential safety hazard.In recent years,with the development of large-scale and high-speed ships,the subsidence of modern ships in restricted waters will increase.If the estimation of the subsidence is insufficient,it will lead to bottom scraping,grounding and other accidents.Therefore,it is of great significance to study the sinking of ships in navigation.The calculation methods of ship subsidence mainly include theoretical calculation,experimental measurement and numerical simulation of real ship and tank.The theoretical calculation method mainly solves the ship's subsidence by solving the hydrodynamic equation or according to the wave-making theory,but the theoretical method has a large amount of calculation,and there are many restrictions in the process of solving.The numerical results obtained by real ship and tank experiments are more accurate,but there are some safety problems in real ship experiments.Especially in restricted shallow waters,tank experiments need to build ship models before experiments and the cost of experiments is higher.In recent years,with the continuous development of computer performance and the continuous improvement of computational fluid dynamics(CFD)technology,more and more researchers are using CFD to study ship sinking.In this paper,the computational fluid dynamics method is used to study the influence factors which affecting the hull sinkage of a ship,which the"Yukun" ship,an intership ship of Dalian Maritime University,is taken as the research object.Firstly,the knowledge of computational fluid dynamics is applied to the calculation of the ship sinkage,and a numerical method for calculating the ship sinkage is presented based on the ship motion model.The discretization error in the numerical method is also analyzed,and the mesh size,discretization format and the optimal time step settings for solving the sinkage are determined according to the actual model.Secondly,the calculation model for calculating the hull sinkage of "Yukun" ship is established based on the numerical method presented above.In order to insure the reliability of the calculation results,the same process is applied to another KCS ship.The reliability of the calculation results is determined by comparing the calculated data of two ship models with the empirical formula.Then,the influence factors of hull sinkage of "Yukun" ship are calculated under different navigation conditions and the influence of ship speed,draught and water depth on the hull sinkage are also analyzed.Finally,the regression equation is drawn by comparing and regressing the calculated figures of hull sinkage of "Yukun" ship under different conditions,which provides a reference for the study of hull sinkage.