Model Test And Fluid-solid Coupling Numerical Simulation Study Of The Diversion Cofferdam

In recent years,in the construction of hydropower projects in the valley with steep terrain,stones excavated from both sides of the dam abutment are often pushed into the river directly to solve the problem of difficult transportation.In the flood season,the stones which are rushed to the downstream by the water will cause water and soil loss and environmental pollution.At this time,the diversion cofferdam is constructed to block the stones in the river.It can not only meet the environmental protection requirements of the downstream,as part of the upstream and downstream cofferdams,the diversion cofferdam can also prepare for the construction of the anti-seepage wall after flood and reduce the filling strength of the cofferdam in the later stage.During the flood season,the stability and safety of the diversion cofferdam,which undertakes part of the water passing task,will be severely tested under the action of water flow.Currently,there are two main methods in the study of the diversion cofferdam,one is the model test and the other is the numerical simulation.Among them,the model test has been able to obtain relatively reliable results,but there are still limitations such as the scale effect,which requires the support of numerical simulation methods.However,there are still few domestic researches on the use of numerical simulation to study the diversion cofferdam.Based on the model test results,the numerical simulation method of fluid-solid coupling is used in this dissertation to study the stability and scouring deformation of the diversion cofferdam of a project under different flow rates,and the results were compared with the model test.The main research contents and conclusions include:(1)According to the basic theory and application of fluid-solid coupling,the current softwares of fluid-solid coupling were compared,and ANSYS Workbench was selected as the platform for bidirectional fluid-solid coupling numerical simulation of the diversion cofferdam.(2)In the model test of the diversion cofferdam,the scouring deformation results of each part under different flow rates were obtained.The water level and velocity distribution and the law of the scouring deformation of the diversion cofferdam were compared and analyzed under different flow rates.(3)Establishing simplified 3d models of the diversion cofferdam and the flow field,using Fluent to analyze the flow field and Mechanical to analyze the diversion cofferdam in ANSYS Workbench,and creating a data exchange between the two through the System Coupling.The water level and velocity distribution of the flow field and the deformation of each part of the diversion cofferdam under the coupling action were obtained by calculation,and verified by the model test results.(4)According to the numerical simulation,there is no cross-section failure or large-scale overall plastic deformation of the diversion cofferdam under different flow rates,indicating that the diversion cofferdam is stable on the whole,which is consistent with the model test results.(5)By analyzing the plastic deformation results of the diversion cofferdam under different flow rates,it can be concluded that the diversion cofferdam has a large plastic deformation at the top and the gentle slope section.And there is one most unfavorable flow rate,at which the plastic deformation is the largest.The plastic deformation results in the numerical calculation have a good correspondence with the scouring position of the diversion cofferdam and its most unfavorable flow rate in the model test,which can provide a reference for the construction of protective structure of the diversion cofferdam in similar projects.