Research On Hydrodynamic Characteristics And Safe Navigation Of KCS Container Ship In Restricted Waters

The rapid development of the shipping industry has driven an increase in the design size of ships,the trend of large-scale ships has amplified the limited impact brought by limited shallow waters.The characteristics of the accelerated flow field around ships in restricted waters and the greater pressure difference around the hull increase the resistance of ships during navigation,resulting in more significant sinking and trim amplitudes.At the same time,as the main maritime transportation method,container ships also bring high emissions due to their high transportation volume.While pursuing navigation efficiency,it is necessary to consider reducing the operating costs of navigation and transportation.Improving the motion characteristics of ships by adjusting their trim and draft is a promising strategy for improving energy efficiency in maritime transportation.Therefore,analyzing the impact of different navigation conditions on ship hydrodynamics of large container ships in restricted shallow water is of great significance for improving navigation efficiency,energy conservation,and emission reduction of large ships in shallow water.In this paper,computational fluid dynamics(CFD)numerical simulation method is used to simulate the trim optimization of KCS container ships in confined waters to reduce resistance and subsidence.The conclusions are as follows:(1)When the draft ratio is h/d=2.2,the simulated data of the total resistance coefficient,subsidence,and trim values at 0.2 to 0.55 Froude numbers are verified with physical experimental results,and the results are in good agreement,confirming the accuracy of the CFD model method.(2)The optimal trim condition for resistance changes with the sailing state,and the increase in ship speed and draft leads to an overall trend of resistance change that can be partially offset by adjusting the trim.Specifically,the longitudinal inclination of the bow is more conducive to achieving smaller resistance than the longitudinal inclination of the stern.When Fn=0.469 and draft ratio is 1.3,the optimization effect is optimal,and the offset effect can reach 6.2%.The change in resistance caused by trim adjustment shows a better effect on pressure resistance compared to frictional resistance.(3)The sinking amount of the ship is caused by the pressure difference between the bow and stern on both sides of the ship and increases with the increase of the ship’s speed.The higher the ship’s speed,the faster the increase in sinking volume,and the increase in stern is greater than the increase in bow.For the same ship speed,an increase in water depth and draft ratio leads to significant sinking of the ship.When the ship speed is Fn=0.55,the sinking increase is most significant with an increase in draft ratio of 150%.Due to the influence of trim,the bow settlement is always greater than the stern settlement.(4)Based on the simulation data of restricted water conditions,this paper analyzes the navigation characteristics and maneuvering difficulties of container ships in restricted water areas.From the perspectives of navigation,maneuvering,and sinking,measures are proposed to control the speed reasonably,apply anti fouling coatings,replace automatic helmets with manual helmets,and maintain ship draft differences,reducing ship speed and continuously using ship depth sounders for depth measurement to promote ship resistance reduction,energy conservation,and emission reduction.