Study On The Overflow Diffusion Characteristics Of Trailing Suction Hopper Dredgers

Dredging engineering carried by trailing suction hopper dredger is widely used in the construction of ports and waterways,construction of water conservancy facilities,dredging of environmental protection,land reclamation,submarine tunnel excavation and deep-sea mining.During its construction,the loading and overflow process is an important part of the treatment of excavated slurry.With the increasing requirements of environmental protection,the related ecological pollution caused by dredging has become a hot spot today,and the diffusion of overflow slurry is one of the sources of pollution generated by dredging suction dredgers.Therefore,combining with actual engineering conditions,this paper adopts the theory of computational fluid dynamics(CFD)to study the diffusion characteristics,diffusion range,and influencing factors and proposes construction strategies to reduce its pollution impact.In this paper,the entire process of overflow diffusion is divided into two parts:near-field diffusion and far-field diffusion.In the near field,the Double-Euler fluid model is used to establish a CFD model of slurry flow and determine the key parameters;In the far field,the particle information is read into the flow field to drive the slurry transfer based on the turbulence model which combines with the Lagrangian method.At the same time,the simulation data are compared with experimental and measured data to verify the accuracy of the model.The details are as follows:(1)Based on the Richardson number(Ri)and velocity ratio(ζ),the key parameters of overflow diffusion in the near field,a three-dimensional numerical simulation of the flow state in the near-field is carried out based on CFD model.The flow characteristics and diffusion distribution characteristics of overflow diffusion under different influence parameters are analyzed and the change trends of the key parameters are summarized.(2)Based on the external influence factors in the actual dredging construction,those are,the impact of the overflow release position,the release frequency,and the propeller at the rear of the ship,the CFD model is used to simulate the near-field overflow diffusion flow under different influence variables.In addition,the diffusion characteristics and concentration distribution of overflow slurry under various working conditions are summarized.Furthermore,some reasonable suggestions are made for environmental protection dredging operations.(3)the sea area near a construction area is selected as the research object in order to study the influence of overflow slurry in the far field.The turbulence simulation model combining with different geographical conditions such as wind field and wave is used to simulate the diffusion process of the overflow slurry in the far field.The diffusion range and concentration distribution of overflow slurry are analyzed in order to comprehensively summarize the impact of the entire process of overflow diffusion and provide guidance for the selection of the construction area.