Numerical Simulation On The Determination Method Of Channel Navigation Width Under Different Cross-flow Conditions

In order to implement the strategic deployment of the construction of a strong transportation country,the construction of China’s inland waterways has also entered a new stage of development.The transport sector issued the "Outline for the Development of Inland Waterways" in 2020,putting forward the requirements of promoting the highquality development of inland waterways,to improve the construction of a modern waterway system with dry and branch connections between rivers and seas,and to accelerate the establishment of international 1,000-ton routes as the backbone,transversely east-west,connected to the north and south,smooth access to The national waterway of high quality with international 1,000-ton routes as the backbone,connecting east and west,north and south,and smooth access to sea ports.However,there are many dry and tributary converging channels in China’s natural rivers,and the converging channels are usually characterised by large drop-offs,narrow,curved channels and rapid currents.As the cross-flow in the main stream is the most important issue affecting the navigable water flow conditions after the tributary convergence.Therefore,based on the two-dimensional mathematical model of water flow and the mathematical model of ship operation movement,this thesis explores the influence of different channel classes and different cross-flow into the confluence on the scale of the main stream channel,with a view to proposing the required channel scale and range of the main stream channel under the condition of large confluence cross-flow formed by sudden flooding of the tributaries,focusing on the additional channel width required,which can provide a basis and reference for the design of the channel at the mouth of the tributaries.The main research elements are as follows:(1)Based on the analysis of the basic equations of the planar two-dimensional water flow mathematical model and the corresponding control equations,the numerical simulation of the planar two-dimensional water flow with water depth averaging is realised by using Fortran language programming.Based on the Changshou Fantuo River section of the Yangtze River main stream,the hydrodynamic parameters such as water level,flow velocity and buoy flow direction were verified,indicating that the twodimensional water flow mathematical model and numerical calculation method are reasonable and can provide more reliable flow field data.(2)Based on the MMG ship manoeuvring motion model,the ship motion equations were solved using the Longe-Kutta method.The mathematical model of ship manoeuvring motion was developed independently from the bottom by using Fortran language programming.The rationality of this ship manoeuvring motion mathematical model was analysed by examining the ship manoeuvring performance using the basic parameters of representative inland river vessel types.(3)Numerical simulation of ship manoeuvring motion under the action of different cross currents was carried out to derive the sailing attitude and navigation parameters such as rudder angle,drift angle,speed against the shore and speed against the water for the representative ships of inland waterways of class Ⅰ to V in different uniform cross current areas.The results show that the ship navigation parameters are not only related to the size of the cross-current,but also influenced by the opposite speed,the scale of the channel,the ship type and the length of the cross-current area.Accordingly,the semitheoretical and semi-empirical expressions of the ship’s cross-drift speed and the safety range of overscale cross-current under the action of different cross-currents are proposed,and the diagram system and method for determining the increase of the net width of the navigable channel under the situation of overscale cross-current are given.(4)Taking the Pinglu Canal project,a new western land and sea channel,as the background,the confluence of typical important tributaries(Guangping River and Shabu River)is selected as a typical river section.Based on the established plane twodimensional water flow mathematical model,the navigable water flow conditions of the typical river section are simulated,and then the numerical simulation of the ship operation movement under the overscale cross-current condition is carried out.The results show that under the conventional channel scale design,the overtopping cross-current at the mouth of the Shabu River tributary is relatively small and can be safely navigated by adjusting the rudder angle.In contrast,the overtopping cross-current in the channel at the mouth of the tributary of Guangping River is larger,and the ship is affected by the crosscurrent and the lateral deflection is more serious,which makes it difficult to guarantee the safe passage of the ship.After the widening of the tributary channel according to the results of this thesis,a simulation study was carried out by the mathematical model of ship manoeuvring,and the results showed that the ship could pass safely.It shows that the widening results and determination methods of the channel under different crosscurrent conditions proposed in this thesis are basically reasonable.