Research And Application Of Three-dimensional Flow And Sediment Mathematical Model Of Spur Dike

Spur dike group in the lower reaches of Luanhe is an important part of river regulation project,but the water damage caused by complex flow structure near spur dike and local scouring at dam head is more serious.This paper establishes a threedimensional flow and sediment mathematical model of spur dike group of Luan River downstream demonstration project to analyze the hydraulic characteristics and scouring characteristics,and evaluates the safety of the spur dike group to provide a theoretical basis for the comprehensive river regulation project and the maintenance of spur dikes.The main contents of the thesis include the following parts:(1)At present,the water and sediment characteristics of spur dike are mostly studied by flume physical model or single spur dikes numerical model,and there are few studies on the water and sediment movement of natural river channels and multiple spur dikes.This paper selects RNG k-ε model and uses VOF to simulate the flow in natural river.The sediment movement model based on Hilz number is used to simulate river sediment movement.In the process,the three-dimensional flow and sediment simulation of spur dike group in natural river channel is carried out.(2)This chapter constructs a three-dimensional flow and sediment model from Jingshan railway to Haikou in the lower reaches of Luanhe,and the flow model is verified by simulating the water level change of 5-year and 10-year constant flow processes.The three-dimensional flow and sediment model of spur dike group of preliminary test project in the downstream dangerous section is established,and the sediment model is verified by comparing the transverse section and longitudinal section of the deepest scour pit with the measured topographic values.The results show that the model is reliable and can be used to simulate spur dike groups under different inflow conditions in the lower reaches of Luanhe River.(3)On the basis of the measured topography and layout of Luanhe downstream demonstration project in 2017,a three-dimensional flow and sediment model of spur dike group is established.The hydraulic characteristics of spur dike group under the conditions of constant flow and unsteady flow in different return periods,including velocity,water level and hydrodynamic pressure,are simulated.The results show that the velocity,water level and hydrodynamic pressure at the head of head dam B1 are the largest,followed by spur dikes B6 and B10.(4)According to the formation and development process of scouring pit at the head of spur dike group,the scouring characteristics of spur dike group are analyzed.The risk and vulnerability calculation formula of spur dike group in the lower reaches of Luanhe is established by analytic hierarchy process.And the safety of spur dikes is evaluated by scoring method.It is found that the safety of head dike B1,spur dike B6 and end spur dike B10 in spur dike group is poor compared with other spur dikes,and maintenance and protection should be strengthened.