Numerical Analysis on Energy Dissipation of Tsunami through Vegetation Zone

Abstract

We have improved a 2-D Numerical Wave Tank (NWT) based on a Porous Body Model (PBM) for the simulation of energy dissipation during the interaction with a tsunami. In order to quantitatively evaluate the energy dissipation by vegetation drag during the process, the fluid resistance with regard to the vegetation and the vegetation drag coefficient according to the Reynolds number were applied. Moreover, to confirm the validity and effectiveness of the improved NWT, the results were compared with the existing numerical experimental results of tsunami vegetation interaction. The comparison showed that the water waveforms of the tsunami around the vegetation zone well are well simulated. As a result, the height of tsunami, the width, the density of vegetation, the reflection of the tsunami by freeboard, and the reflection and transmission characteristics of the tsunami were confirmed. In addition, the characteristics of the decrease in the energy of the tsunami as it passes through the vegetation zone were analyzed. As the vegetation width, height, and density increase, the transmission coefficient decreases, the decrease in the energy increases, and the reflection coefficient does not change significantly. In addition, since a vegetation zone with a large porosity gradually decreases the energy, the decrease in the energy becomes clear as the vegetation width increases.