• Title/Summary/Keyword: Tsunami-vegetation interaction

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Effects of Tsunami Waveform on Energy Dissipation of Aquatic Vegetation (쓰나미 파형이 수중식생의 에너지소산에 미치는 영향)

  • Lee, Woo-Dong;Park, Jong-Ryul;Jeon, Ho-Seong;Hur, Dong-Soo
    • Journal of Ocean Engineering and Technology
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    • v.31 no.2
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    • pp.121-129
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    • 2017
  • The present study numerically investigated the influence of the waveform distribution on the tsunami-vegetation interaction using a non-reflected wave generation system for various tsunami waveforms in a two-dimensional numerical wave tank. First, it was possible to determine the wave attenuation mechanism due to the tsunami-vegetation interaction from the spatial waveform, flow field, vorticity field, and wave height distribution. The combination of fluid resistance in the vegetation and a large gap and creates a vortex according to the flow velocity difference in and out of the vegetation zone. Thus, the energy of a tsunami was increasingly reduced, resulting in a gradual reduction in wave height. Compared to existing approximation theories, the double volumetric ratio of the waveform increased the reflection coefficient of the tsunami-vegetation interaction by 34%, while decreasing the transfer coefficient and energy attenuation coefficient by 25% and 13%, respectively. Therefore, the hydraulic characteristics of a tsunami is highly likely to be underestimated if the solitary wave of the approximation theory is applied for the tsunami.

Application of 3-D Numerical Wave Tank for Dynamic Analysis of Nonlinear Interaction between Tsunami and Vegetation (쓰나미-식생 비선형 상호작용의 동적해석을 위한 3차원 수치파동수조의 적용)

  • Lee, Woo-Dong;Hur, Dong-Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.36 no.5
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    • pp.831-838
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    • 2016
  • The disaster preventing system using vegetation has been growing in the field of coastal engineering in recent years. To analyze wave and flow fields under nonlinear interactions between tsunami and vegetation, the purpose of this study is to evaluate newly-developed 3-D numerical wave tank including energy dissipation by tsunami-vegetation interaction based on existing N-S solver with porous body model. Comparing numerical results using mean drag coefficient and dynamic drag coefficient due to Reynolds number to existing experimental results it is revealed that computed results considering the dynamic drag coefficient are in good agreement with the laboratory test results for time-domain waveform. In addition, the calculated transmission coefficients of solitary waves in various vegetation densities and incident wave heights are also in good agreement with the experimental values. This confirms the validity and effectiveness of the developed 3-D numerical wave tank with the fluid resistance by vegetation.