| dc.description.abstract | In this study, we use a 3D numerical model to simulate the processes of tsunami run-up. The study case is the Mentawai tsunami happened in October 25, 2010. The field survey showed an interesting phenomenon that most of the vegetation inland was destroyed, while, in contrary, only limited damage observed at the coastal area. Because a steep cliff is located right behind this area, we assume that this special topography might be one of the reasons. If this hypothesis sustains, the hillsides buildings might also under the tsunami threat. To study this case, the numerical method is adopted. Validation with experimental data and Sibigau tsunami simulation are included.
As for the model validation, the simulation results are compared with the experimental data obtained from Professor Zhenhua Huang in Singapore Nanyang Technological University. In the experiment, a solitary wave is used to represent the tsunami incident wave. The force and bending moment from the run-up bore acting on a small circular cylinder are recorded. Our numerical model solves 3D Large-Eddy Simulation（LES）model, and estimate the tsunami force by Morison formula. The result shows that the numerical model is able to predict the bore height and velocity field accurately, and reasonable accuracy on the force prediction.
We also study the flow characteristics of three cliff angles. The result shows that the rebounded bore is presented in all of the cases. This rebounded bore causes the second impact on the structures at the toe of the cliff. It might explain phenomenon observed on Sibigau Island. To confirm this hypothesis, this study precedes the overflow simulation in the real scale.
The complete tsunami simulation on Sibigau Island is divided into two parts. The first part is the 2D simulation of the Mentawai tsunami by COMCOT model. Three layers of nested grids are adopted. The third layer focuses on Sibigau Island with a resolution of 120m. The second part is the 3D simulation by LES-VOF model. The third-later COMCOT result is adopted as the inflow boundary condition. The result shows that the tsunami waves transforms into tsunami bores, and then rebound after reaching the hill. The position of the rebounded wave consists with the field observation.
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