| The common layout form in the plane layout of the port is the dug-in harbor basin.Because the dug-in harbor basin is a typical cecal reach,there is a common reflux movement in the harbor basin.The sediment diffused from the mainstream enters the harbor basin and deposits near the entrance of the harbor basin and in the harbor basin,which affects the normal operation of the harbor basin.At present,the research on the siltation of the excavated harbor basin is mainly based on the indirect analysis of the sediment deposition mechanism from the flow movement characteristics,because the water body in the excavated harbor basin is a mixed phase fluid of water and sand,therefore,only an accurate model can be used to truly reflect the flow movement characteristics in the harbor basin,and at the same time,the siltation mechanism of the harbor basin can be understood from the point of view of sediment deposition.The main work of this paper is as follows:(1)A two-dimensional flow numerical model of excavated harbor basin is established by Mike,and the flow characteristics of different forms and flow conditions of excavated harbor basin are analyzed.The solution of riverbed evolution model involves four aspects: initial value condition setting,boundary condition setting,dry and wet boundary treatment and hydraulic structure treatment.Finally,riverbed evolution model and sediment transport model are obtained.(2)A three-dimensional numerical model of water flow is established by Flow-3D.The establishment of the model includes Nmurs continuity equation,Nmurs momentum equation,free liquid surface treatment and turbulence model.The discretization and iterative methods are used to solve the model,and the flow pressure field and velocity field are obtained.(3)Analyze the three-dimensional flow structure of Youbu,Luoyang,Nunbu and Zhoushang excavated harbors.Based on the actual data,the boundary value conditions,initial conditions and working conditions are set,in which 30 °,60 °and 90 °schemes are adopted for the excavated harbor ponds in Youbu,Luoyang and Zhoushang,and25 °,45 °and 90 °schemes are adopted in the female port excavated harbor ponds.The water depth,surface velocity distribution and three-dimensional streamline of different schemes are compared and analyzed.For different harbors,the reflux is mostly formed near the entrance,and the shape is close to the ellipse.After the diversion of a part of the water body,the radial specific drop is formed under the action of centrifugal force and gravity,and the radial circulation is formed.(4)Simulate the suspended load scour and deposition deformation of each river reach,analyze the trend of interannual erosion and deposition and multi-year sediment erosion and deposition,determine the main deposition position,and select a reasonable port site.The schemes of 30 °,60 °and 90 °are adopted for tourist ports,Luoyang and Zhoushang excavated harbors,and 25 °,45 °and 90 °schemes are adopted for female ports.In this paper,the sediment deposition of different schemes of Youbu,Luoyang,Nubu and Zhoushanggang ponds are compared,the mechanism of siltation is analyzed,and the minimum scheme is selected.For the straight and slightly curved convex bank river shape,the smaller the harbor basin axis angle is,the smaller the silting amount is;for the slightly curved concave bank river shape,there is no obvious relationship between the silt amount and the harbor basin axis angle.(5)To study and compare the silting thickness and concentrated silting area of different river sections,and to find out the mechanism of sediment deposition.It is found that the three-dimensional flow vortex in the harbor basin is consistent with the sediment deposition position,and it is considered that the siltation mechanism of suspended sediment in the harbor basin is eddy turbulence dissipation and energy dissipation.Finally,the optimal layout scheme of excavated harbor basin and the key technology of silt reduction are put forward. |
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