| Summary: | 碩士 === 國立中央大學 === 水文與海洋科學研究所 === 102 === Three tsunami boulders were found at the Jiupeng coast in the Southeastern Taiwan (Matta et al., 2013), and can be the evidence of a paleotsunami event happened within 5000 years. In this study, we intended to reconstruct this tsunami event and learn the potential large tsunami that might attack the southern Taiwan. The first step is to find the possible tsunami sources by means of tsunami reverse tracing method (TRTM). TRTM is developed based on the linear wave theory and dispersion relationship. By TRTM, we can also rule out the impossible ones. As the probable tsunami sources are located, the second step is to setup the tsunami scenarios, and to eliminate the cases with results contradicted with the relationship between bore height, or velocity, and displacement of tsunami boulder, which can be derived from 3D fluid-solid two-way coupling model. The result of reverse tracing method shows that only the tsunamis from Ryukyu, Manila, and Yap Trenches are able to reach the coast of Jiupeng.
In terms of the tsunami hazard mitigation, a coastal structure may be able to protect the shore from being attacked by a tsunami. In this thesis, we intend to study the energy dissipation from a circular plate in a solitary long wave by means of three-dimensional numerical simulations, SPLASH3D. For the model validation, we performed 2D simulations with a solitary wave interacting with a flat plat and compared our results with the analytical solutions and experimental data proposed by Prof. Philip L.-F. Liu at Cornell University, USA (Lo and Liu, 2014). We found that the numerical solutions were very close to the analytical solutions and experiment data. After that, we utilized our model to the 3D simulation of interaction between solitary wave and submerged circular plate. The simulations were also compared with the analytical solutions (Lo and Liu, personal communication). When the nonlinearity increased, deviation between simulation and analytical result became more obvious. A steep and nearly breaking wave was observed above the circular plate. Cases with different submergence were compared, and the circular plate play a role of pressure shield, especially in cases with smaller submergence, which caused a pressure gradient induced local flow field and a strong vortex rings were also presented around the edge of the plate. Besides, smaller submergence had greater effect on energy dissipation and wave height of transmission wave.
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