The Impacts of Velocity and Sediment Concentration Profiles on The Behavior of Shear Flow over Erodible Bottom

• Main Authors: Kuan-ChihWang, 王冠智
• Other Authors: Y.C.Tai
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/07833297104871024624

碩士 === 國立成功大學 === 水利及海洋工程學系 === 103 === When the earthquake or heavy rainfall occurs, it may induce collapse. The shattering rocks and soil would block the channel and form a natural dam. Then the barrier lake will be generated behind the natural dam. The basal surface will evolve intensely due to the erosion or deposition during the process of dam breaks. In present study, we consider the fluid as a three continuous layer, pure water, mixture transport, erodible bed layer. And we regard the mixture layer as a shear layer; its concentration is different with bed layer. The surface between the mixture layer and erodible bed is a non-material singular surface, so we can use the mass and momentum jump condition, which the bottom of mixture layer has a sliding velocity and depth-integrated to derive the government equation. As the erosion and deposition have distinct mechanisms, we recommend that the erosion and deposition have to be treated separately. Then we can see the influence of these assumptions on the run-out zone, fluid thickness and the erosion/deposition rate. Owing to the basal surface evolves intensely, in this paper, we use Unified Coordinate to describe the development of dam-break shear flow on deforming basal surface. For the numerical scheme, we use a shock-capturing non-oscillatory central (NOC) scheme to simulate the variation of basal surface, and discuss the influence of fluid on different sliding velocity and fluid configure. Finally, we combine the Unified Coordinate, different concentration profile assumption, sliding velocity and new erosion mechanism. Our simulation had a good agreement with the experimental result, but the location of the boundary of transport layer and the bed is not precise enough, we postulate if we employ a diverse erosion equation and deposition equation, we may be able to correct this phenomenon and get a better result.