碩士 / 國立中央大學 / 水文所 / 97 / When a tsunami wave propagates to the near-shore region, it transforms from a long wave to a tsunami bore and dissipates the energy in the coastal region. This is the most destructive period during the whole tsunami life. In order to have better understanding on the tsunami bore, this paper investigates the physical processes of a dam-break bore which has similar behavior as the tsunami bore. The bore-structure interaction is studied by placing a square cylinder at the downstream region. The numerical approach is adopted. We solve the 3D incompressible Navier-Stokes (NS) equations with large-eddy simulation (LES) turbulence model. The free-surface kinematics and wave breaking are tracked by the volume-of-fluid (VOF) method. The domain is discretized by the finite volume method (FVM) with an irregular mesh domain. The broken dam is modeled by the moving-solid algorithm (MSM) to detailed describe the lifting motion of the gate. The dam-break bore is marching in a channel with a length of 14.72 m to mimic the quasi-uniform tsunami bore. The numerical results are validated with the laboratory experiments in terms of the wave force acting on the square structure. We focuses the discussions on the effect of the impoundment height, waterbed lubrication, gate motion, free-surface profiles around the broken-dam and square cylinder, pressure profile around the cylinder. The results show that the impinging force on the cylinder is mainly determined by the impoundment, width of the channel, and the projected area of the structure. However, it also sensitive to the thickness of the waterbed and the lifting speed of the gate. When the bore is impinging with the cylinder structure, two eddies with inversed rotation direction will be generated right in front of the structure. Their length scales are similar to each other and close to the thickness of the incoming bore. The largest wave fore acting on the cylinder is not located at the bottom but at half of the incoming bore height. This indicates that the maximum impinging force is dominated by the hydrodynamic pressure. The waterbed plays a lubrication role which accelerates the bore speed and increases the wave force.
| Identifer | oai:union.ndltd.org:TW/097NCU05761006 |
| Date | January 2009 |
| Creators | Miao-Shan Wei, 魏妙珊 |
| Contributors | Tso-Ren Wu, 吳祚任 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 149 |
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