Study Of Outburst Flood Flow Attenuation Effects Caused By The River Suddenly Shrunken

Recently, increasing extreme weather and hazards lead to frequent outburst flood in our southwest country, owing to the unique and fragile natural environment, outburst flood in this area is active, which often washed out roadbed and destroyed the building and bridge. Outburst flood events threaten local facilities of human-being, development in economic, causing an urgent in proper hazard mitigation measures.This thesis is presented in Palongzangbu watershed in Tibet plateau. Firstly, outburst flood is investigated and analyzed with the case (1998) in Midui Ice River by field investigation, model tests and theory analysis. Then depending on model test and the numerical simulation, the velocity of water and the height of water are most important things to learn the attenuation of water flow caused by the sudden decreased width of the stream way when the break flood pass is also a problem we concern about. Finally, according to a lot of numerical simulation, the attenuation of outburst flow is poorly-understood in investigations of factors that the width of steam way is suddenly decreased.FLUENT-a influential computational fluid dynamics(CFD) software is used to simulate the flow field of the attenuation coefficient in this paper. After selecting the mathematical modal exactly and defining the boundary condition accurately, this thesis simulates the flow field of the normal attenuation coefficient, with water as medium. The correctness of the simulation result is checked up in according to the vortex and flood flow theories and some testing result. Main results are showed as follows:1. The ratio of different width is decisive factor to the situation of slowly rising water, while the size of water flow is secondary factor. And conclude the form of water flow attenuation coefficient.2. The ratio of different width is also decisive factor to the situation of break flood. The flood scale is less important factor of attenuation coefficient. The influence of flood scale is just 10 percent.3.According to the numerical simulation results, control the different section as a variable and research the velocity and height of different flood flow when it through different section. We can find the ratio of the flood flow and provide some advice about Disaster reduction measures of Line engineering.