Dam-Break Flood Wave Modeling Using the Matched Asymptotic Expansions Method
Date Issued
2011
Date
2011
Author(s)
Yu, Fu-Chiun
Abstract
This thesis attempts to investigate the dam-break problem. We construct two models to approach the problems with different conditions in this study. The first one is the clear water model, and the second one is the water and sediment mixture model. The shallow water equations and Manning’s formula are used in the first model. The initial state is that a point source floods released from dam-break. And the wave propagates downstream in a dry sloping channel. We derive the solutions of the governing equations using the method of matched asymptotic expansions. The results are compared with the other model with different friction slope formulas. The comparison between the model and others shows good agreement. The flow-sediment continuity and momentum equations, sediment discharge and Manning’s formulas are used in the second model. The initial state is similar to that in the clear water model. But in the second proposed model, there exists some initial flow depth downstream of the dam and the channel bed is sediment-laden. When the flood wave passes to the downstream, the sediment layer might be subject to souring. As such, sediment concentrations in the flood wave will increase. We also use the matched asymptotic expansions method to solve the governing equations in the second proposed model. The variation of the sediment layer might be of smaller order of magnitude compared with that of the water depth. Nevertheless, results demonstrate that the spatial lag exists between the flood wave and the sediment layer. The effects of the various conditions are discussed. The results show that the channel slope and sediment diameter are two of the most important parameters in the second proposed model.
Subjects
Dam-break problems
Method of matched asymptotic expansions
Sediment transport
Sediment concentration
Spatial lag
Type
thesis
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