Investigation On Dike-break Induced Flows By Applying Physical Model And Numerical Simulation

River dikes play important roles in flood control and water resource utilization.While dike projects will face the risk of failure when the flood exceeds the design level.Dike breaking is one kind of the frequent disasters in the world and it could cause enormous losses.Therefore,attention should be attached to the study of dike-break induced flows.So far,numerical models are widely used to simulate the flooding due to dike-break,while direct observations from field surveys and physical models are rather limited.Moreover,unlike the dam break from reservoirs at rest,the dike-break flood is influenced by the main flow direction of the river.The research results of dam-break could not apply to dike-break directly.In this study,both physical experiments and numerical models are used and focus on the basic dynamics of water.Boundary conditions are simplified to highlight the propagation characteristic of the flow in different areas.Physical experiments have been conducted in a large laboratory flume to simulate dike-break induced flood wave propagations in flooded area and flow fluctuations in channel.The variations of water level and discharge are measured and investigated by using a pressure sensor array and two ADVs(Acoustic Doppler Velocimetry).DIVAST-TVD numerical model is adopted which base on Shallow Water Equations.These equations are broadly used to describe coastal,estuarine,inland water flows and will be solved by the TVDMacCormack numerical scheme.Model calculation results are compared with the measured data to ensure its reliability.Then the numerical model is used to describe the velocity distribution of the dike-break flood and explore factors affecting the flow through the breach as complement and extension to experiments.The results show that:(a)the change process of water flow induced by dike-break can be divided into three different stages: the initial stage when the gravity has the main impact on flow,the transitional stage when the river discharge replace gravity guadually becoming the leading role,and the stable stage when the river discharge hasthe main affect;(b)in flood plains,river discharge makes the dike-break indued flow deflected downstream,and greater river discharge makes greater degree of deviation within a certain range;(c)in river channel the dike-break induced water dropping caused asymmetrical waves,which propagate slower upstream with greater amplitude and propagate faster downstream with smaller amplitude;(d)the rate of flow through the breach varied over time,the peak appears in the initial stage and the steady flood flow rate is related to the difference of discharges between the upstream and downstream sections.The study results could provide reliable materials for dynamics analysis of dike-break flows,for verifications of other numerical models and then for the benefit of flood prevention and disaster control in riverine managements.