IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Poster presentation 1806
Study on behavior of drifting bodies due to tsunami and its numerical
simulation using EDEM
Mr. Naoki Fujii
Port and Coastal Engineering Department Tokyo Electric Power Services Co.,Ltd IASPEI
Ken Yanagisawa, Fumihiko Imamura
When large earthquakes such as Tokai and Tonankai in happen, the coastal area in particular industrial
zone would suffer damage due to tsunami. The damage of the structure is basically classified into two
types. The first is caused by hydrodynamic force of tsunami itself, and drifting bodies due to tsunami
causes the other one. Ships, cars and destroyed objects could be drifting bodies. As seen in 2004 Indian
Ocean Tsunami, drifting/floating bodies together with tsunamis attacked to coastal area and destroyed
the offshore and land structures. The importance of such kind of tsunami effect is realized recently.
Therefore it is an important to develop the tool for predicting behavior of the drifting bodies interacted
by the tsunami at coastal area. In this study, a behavior of drifting bodies due to tsunami is investigated
and modeled. Firstly, experimental tests are carried out. Secondly, we introduce Extended Distinct
Element Method -EDEM- into numerical simulation to reproduce experimental results. This EDEM has a
characteristic to be able to express various shape of drifting bodies by connecting among several
elements. In order to understand the behavior of drifting bodies, especially in complex stream regime,
we carried out drifting experiment with a harbor in large two-dimensional wave tank. The behavior of
drifting bodies is measured its displacement and drifting path by the video system. Several notable
behaviors of drifting bodies were observed, such as rotation with vortex occurred in the harbor, running
on the land and running over the breakwater. Secondly, we aim to develop the model of drifting bodies
with EDEM, which consists of several elements connected by spring, dash pot and slider, and can take
into count hydrodynamic force for drifting bodies on the sea. Tsunami simulation with nonlinear long
wave theory gives temporal velocity on each element. Horizontal force acting on drifting bodies is
calculated by Morrisons equation. Vertical force is calculated by buoyancy based on the tsunami wave
height, gravity and drag force. The drifting behavior is calculated by solving the momentum equation
based on the horizontal/vertical forces. The feasibility of EDEM is discussed through comparisons with
the result of experiments. We made the numerical simulation model for the behavior of drifting bodies
due to tsunamis based on a physical experiment. As a result, it is confirmed that EDEM can reproduce
well the behavior of drifting bodies due to tsunami, including complex behavior such as rotation in the
harbor, running on the land and running over the breakwater.
Keywords: tsunami drifting body, extended dem