| Summary: | 碩士 === 國立臺灣大學 === 生物環境系統工程學系暨研究所 === 90 === Compound channels are common in the natural rivers. Because the characteristics of main channel and floodplain are different, it will lead to the property far from that of simple channel. In this thesis, we present an unsteady flow model considering the characteristics of compound channels. This model is based on the divided-channel method. This method divides a compound channel into three parts: main channel, left, and right floodplain, and the three parts are regarded as individual channels. In this model, the water levels of three channels are assumed to be the same, and the geometric transfer will appear in the interface between the main channel and the floodplain. This model can simulate the flux, depth, and geometric transfer respecting to the time in main channel and floodplain. We analyze the hydraulic property of different channel width and friction by simulating different kinds of channels. Two viewpoints are compared: one is the single channel method, in which the compound channel is considered as a uniform channel; the other one is off-channel method, in which the floodplain is assumed as the volume for storing water, not transporting the flux. This model is verified and compared with the experiments in other literatures. The results simulated by this model show a good agreement with the natural conditions of compound channels in any depths. And it avoids the mistakes that the depths are over-predicted in the viewpoints of the single channel and off-channel methods.
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