| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 106 === Steep slope and severe bed change are the general characteristics of Taiwan’s rivers. In order to reduce the risk of disaster, it is an important issue to analysis the impact of local scour around the hydraulic structures on the channel. However, the two-dimensional mobile-bed models are widely used for complex three-dimensional flow field and local scour problems, such as the vicinity of piers, spur dikes, aprons, etc. It is inadequate because of the use of section-averaged or depth-averaged velocity, in the case where the flow velocity distribution along the direction of water depth is significantly different.
In this study, a mechanism for improving the local scour around structures in the two-dimensional mobile-bed model is proposed. The sediment repose angle formula is included in the mechanism. The CCHE2D model is selected to simulate the experimental case and Xiangyuanjia Embankment case in Zhoushui River for the model calibration, validation and comparison.
When the proposed mechanism is included in the two-dimensional mobile-bed model, it can improve the simulated accuracy of the local scour around spur dikes in different scale cases effectively. According to the simulated results of the experimental and field’s cases, the sediment particle size of the scour hole is gradually increased during the scouring process. The scour hole side slope is steep at upstream of the spur dike, it is most affected by the sediment repose angle.
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