# Urban Coast Design

Developing the leading technology in computational science of fluid flow (solid-gas-liquid multiphase flow) by using the particle method for predicting flood flows due to tsunami, storm surge and extremely heavy rain, and for improving water quality to preserve waterfront environment (e.g. aeration and sand capping on underwater mud).

In addition, development of the Lagrangian simulator of crowded people, similar to the particle method, is conducted for promoting a crowd evacuation planning in various disasters.

We aim for establishment of the methodology of computational science and engineering, to describe various phenomena in civil engineering by a fluid/granular-material analogy.

## Academic Staff

### Hitoshi GOTOH

Professor (Graduate School of Engineering)

**Research Topics**

To develop the new computational technology of flow and wave in natural environment with the aim of the advanced design of hydraulic structures in waterfront space, I am conducting the basic researches in the computational hydrodynamics by using two key tools:

- the Lagrangian particle method to track the complicated behavior of water surface; and
- the numerical movable bed to describe the dynamic characteristics of the sediment transport process.

**Contacts**

Room 102, Bldg. C1, Katsura Campus

TEL: +81-75-383-3309

FAX: +81-75-383-3311

E-mail: gotohparticle.kuciv.kyoto-u.ac.jp

### Eiji HARADA

Associate Professor (Graduate School of Engineering)

**Research Topics**

I take charge of the R&D of two topics: 1) Numerical Movable Bed Simulator and 2) System of Particle-Base Human Behavior Simulator. In the former topic, mechanics of sediment-laden flows are investigated from viewpoint of sand particle scale level by using solid/liquid two-phase flow model computationally. And the latter topic, simulation for crowd evacuation process against tsunami is performed, for example.

**Contacts**

Room 101, Bldg. C1, Katsura Campus

TEL: +81-75-383-3310

FAX: +81-75-383-3311

E-mail: haradaparticle.kuciv.kyoto-u.ac.jp

### Hiroyuki IKARI

Assistant Professor (Graduate School of Engineering)

**Research Topics**

I examine the extension and practical application of a particle method as a tool to predict a hydrodynamic force acting on a coastal or river structure in detail. I also develop a fluid-soil interaction model by a particle method to simulate a large deformation of soil due to wave or current.

**Contacts**

Room 115, Bldg. C1, Katsura Campus

TEL: +81-75-383-3312

FAX: +81-75-383-3312

E-mail: ikariparticle.kuciv.kyoto-u.ac.jp

## Research Topics

### Particle method for computational dynamics of free-surface flow - Simulation of breaking wave and violent flow -

A broad definition of a "particle method" is a interactive model of discrete elements. In this sense, both of the MPS method and the DEM which we principally use belong to a particle method. On the other hand, "particle method" of a narrow sense means a gridless solver of the Navier-Stokes equation. As for this kind of particle method, the SPH method and the MPS method are used broadly. By Eulerian methods using fixed calculation points in a computational grid, it is not easy to track a complicated behavior of water surface with a fragmentation and a coalescence of water. In a particle method, particles play a role of Lagrange calculation points interacting each other, hence each term of the Navier-Stokes equation is discretized as an interaction between particles. Therefore, complicated behavior of water surface can be tracked by a simple algorithm.

To estimate information, such as a wave force, wave overtopping discharge, and so on, effectively in a coastal structure design, a numerical wave flume on the basis of particle method is developed, as a simulation tool of three dimensional wave field. Parallel computing to track super 1,000,000 particles, and boundary connecting technology with a particle method and a depth-averaged model represented by the Boussinesq model are introduced.

A staircase is only a route of evacuation form underground space in urban flood. Understanding of physical property of a flow in a staircase is essential to estimate the critical state that a person can climb against an inundating flow. Because a flow measurement is difficult in violent flow in staircase, computational dynamics based on the particle method is conducted. In Fig.1, the result of calculation is shown.

Figure 2 shows calculated result of the tsunami flood with drift woods colliding with girder bridge. Particle method with floating body model is effective to describe a violent flow with a wave breaking with many floating bodies on a water surface. Some animations of calculation by MPS method are shown on our laboratory's web site.

Figure 1. Flow in staircase

Figure 2. Tsunami flood with drift woods colliding with girder bridge

### Computational mechanics of sediment transport - Application of multiphase flow model and granular-material model to movable bed phenomena -

Because bottom boundaries of natural stream in river and coast are mostly constituted by sediment, sediment hydraulics for the flow over movable bed plays a primal role in river and coastal engineering. In our laboratory, the basic researches in the computational mechanics of sediment transport are conducted. Numerical simulator of flow over movable bed is being developed on the basis of mechanics of multiphase flow and granular material, to describe the interaction between flow and sediment particle and inter-sediment collision. This tool is called "Numerical Movable Bed." Some references and book of the computational mechanics of sediment transport are shown on our laboratory's web site.

### Computational science of crowded-people behavior by particle system model - Simulation tool for people evacuation planning in natural disasters -

Simulation of crowd evacuation is a convincing tool of an evacuation planning in a flood. Because an individual-base particle system model treats a personal behavior directly, it is most suitable for a reproduction of detail of an evacuation process. Quick evacuation is indispensable for survival of local inhabitants hit by Tsunami directly. Hence preparing safe evacuation route is quite important. However reproduction of imminent situation in a real disaster is impossible in a ordinary evacuation training and there is no means how to choose the appropriate evacuation route. To overcome this difficulty, a crowd-evacuation simulation to reproduce process of the crowd-evacuation action in a human-scale must be constructed. Fig. 3 shows the evacuation of 880 people from the small town to the hill top at its backside. By extending the capacity of this simulator to few million people, we intend to construct "Virtual City" as a tool of social experiment. Some animations of calculated results are also shown on our laboratory's web site.

Figure 3. Evacuation from huge tsunami