Comparison of Coupled and Uncoupled Alluvial-Channel Sediment Transport Models

• Main Authors: ChunHunTzeng, 曾春渾
• Other Authors: JinnChuangYang
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/71381733993465955926

碩士 === 國立交通大學 === 土木工程系 === 89 === This study investigates the differences and restrictions of coupled and uncoupled alluvial-channel sediment transport models through sensitivity and stability analyses. The uncoupled model assumes the change of sediment variables is small enough during a computational time step, so that its effect on variables can be ignored. Therefore, the flow and sediment equations can be solved separately in one time step. The coupled model solves all of the governing equations simultaneously, and the mutual iteration of the flow and sediment variables are considered. The coupled and uncoupled models used in this study have the same governing equations, sediment transport formula and the numerical scheme. First, the effect caused by numerical weighting factor and mixing layer thickness is analyzed. The numerical dimensionless parameters are derived from governing equations. The influence of the dimensionless parameters to the deviation of bed change and mean particle size has been quantified by numerical experiments. The relation between the deviations and the dimensionless parameters has been constructed as a base function for the sensitivity test of both of the coupled and uncoupled models. The results indicate that there exists an instability problem for the uncoupled model. While the simulation is progressed, one has to consider several parameters simultaneously to ensure the accuracy and stability of the results. From the dimensionless parameters multi-regression relation, one can observe that the sensitivity of simulation results of the coupled model is higher than the uncoupled model.