Kazuo Kashiyama

Development of Simulation System for the Disaster Evacuation Based on Multi-Agent Model Using GIS

Abstract This paper presents a simulation system for the disaster evacuation based on multi-agent model considering geographical information. This system consists of three parts, the modeling for the land and buildings using GIS data, the analysis of disaster evacuation using multi-agent model, and the visualization for the numerical results using the virtual reality technique. By introducing the numerical solver of the natural disaster to the present system, it is possible to evaluate not only the damage of structure but also the damage of human being. Furthermore, it is possible to investigate the appropriate evacuation route by the simulation. The Dijkstra algorithm is used to obtain shortest route to the refuge. In addition, the visualization using virtual reality technique is curried out to understand the feeling of refugee. The present system is applied to the evacuation analysis by the flood flow in urban area and is shown to be a useful tool to investigate the damage by natural disasters.

Parallel finite element methods for large-scale computation of storm surges and tidal flows

Massively parallel finite element methods for large-scale computation of storm surges and tidal flows are discussed here. The finite element computations, carried out using unstructured grids, are based on a three-step explicit formulation and on an implicit space-time formulation. Parallel implementations of these unstructured grid-based formulations are carried out on the Fujitsu Highly Parallel Computer AP1000 and on the Thinking Machines CM-5. Simulations of the storm surge accompanying the Ise-Bay typhoon in 1959 and of the tidal flow in Tokyo Bay serve as numerical examples. The impact of parallelization on this type of simulation is also investigated. The present methods are shown to be useful and powerful tools for the analysis of storm surges and tidal flows.

ALE finite element method for FSI problems with free surface using mesh re-generation method based on background mesh

This paper presents an arbitrary Lagrangian–Eulerian (ALE) finite element method for fluid-structure interaction (FSI) problems with a free-surface using the mesh re-generation method. The mesh re-generation method using the background mesh is introduced to improve the applicability to the complicated FSI problem with large deformed interface. The incompressible Navier–Stokes equation based on ALE description is used as the governing equation of fluid. The stabilization method based on the SUPG/PSPG method is employed. The presented method is applied to several numerical examples to show the validity and efficiency of the method.

A parallel finite element method for incompressible Navier–Stokes flows based on unstructured grids

Abstract This paper presents a parallel finite element method for the large scale computation of incompressible Navier–Stokes flows using unstructured grids. The streamline upwind/Petrov–Galerkin (SUPG) formulation is employed to improve the numerical stability and accuracy and the pressure stabilization matrix (PSM) is introduced to avoid the occurrence of the checkerboard pressure mode. For the finite element, the velocity-tri-linear/pressure-piecewise constant (Q1/P0) element is employed. The pressure Poisson equation is parallelized with the element-by-element scaled conjugate gradient (SCG) method. Parallel implementation of the unstructured-grid-based formulation is carried out on the Hitachi Parallel Computer SR2201. The effect of parallelization on the efficiency of the computations is examined.

EULERIAN FINITE COVER METHOD FOR SOLID DYNAMICS

In order to deal with the kinematic and dynamic boundary conditions in the Eulerian framework, we develop an Eulerian finite cover method (FCM) for large deformation solid dynamics by incorporating the approximation strategy of the FCM into the existing Eulerian explicit finite element method. The operator split method is employed to solve Eulerian solid dynamics problems, and the resulting numerical algorithm consists of two steps. One is the nonadvective step, in which the standard Lagrangian FC analysis is carried out with the explicit time integration scheme, and the other is the advective step, in which the CIVA method is applied to project the solution obtained in the nonadvective step to the Eulerian mesh. Two representative numerical examples are presented to validate the proposed Eulerian FCM and demonstrate its capability especially in appropriately treating the kinematic and dynamic boundary conditions.

A Taylor–Galerkin-based finite element method for turbulent flows

A finite element method is applied to solve the two-dimensional turbulent channel flows. Based on the fractional step techniques, the momentum and the k- equations are split into convection and diffusion equations. The convection equations are solved by the second-order Taylor-Galerkin finite element method, which can overcome the spurious oscillations with minimal artificial diffusion, and the diffusion equations are solved by the fully explicit Galerkin method. Since the same order interpolation is used for the velocity, pressure and turbulent quantities, the present method is computationally efficient. The sudden expansion flow and the obstructed turbulent channel flow are studied. The results are in good agreement with experimental observations.

Large scale finite element modeling, simulation and visualization for wind flows in urban area using virtual reality

A large-scale finite element modeling, simulation and visualization for wind flows are presented. The modeling method using GIS/CAD data is employed. The stabilized parallel finite element method based on SUPG/PSPG method is employed for the analysis of wind flows. The present method is applied to the simulation of wind flow and contaminant spread in urban area. The visualization based on virtual reality is employed to evaluate the mesh quality and computational results. The computed results are qualitatively in agreement with the experimental results and actual phenomena. The present method is shown to be a useful tool to simulate the wind flows in urban area.

IMMERSIVE VR VISUALIZATIONS BY VFIVE PART 2: APPLICATIONS

VFIVE is a scientific visualization application for CAVE-type immersive virtual reality systems. The source codes are freely available. VFIVE is used as a research tool in various VR systems. It also lays the groundwork for developments of new visualization software for CAVEs. In this paper, we pick up five CAVE systems in four different institutions in Japan. Applications of VFIVE in each CAVE system are summarized. Special emphases will be placed on scientific and technical achievements made possible by VFIVE.

Development of an Accurate Urban Modeling System Using CAD/GIS Data for Atmosphere Environmental Simulation

This paper presents an urban modeling system using CAD/GIS data for atmosphere environmental simulation, such as wind flow and contaminant spread in urban area. The CAD data is used for the shape modeling for the high-storied buildings and civil structures with complicated shape since the data for that is not included in the 3D-GIS data accurately. The unstructured mesh based on the tetrahedron element is employed in order to express the urban structures with complicated shape accurately. It is difficult to understand the quality of shape model and mesh by the conventional visualization technique. In this paper, the stereoscopic visualization using virtual reality (VR) technology is employed for the verification of the quality of shape model and mesh. The present system is applied to the atmosphere environmental simulation in urban area and is shown to be an useful planning and design tool to investigate the atmosphere environmental problem.

Large scale finite element simulation and modeling for wind flow and rainfall

A large-scale finite element simulation and modeling method for environmental flows is presented. The stabilized parallel finite element method based on SUPG/PSPG method was employed. The present method was applied to the simulation of wind flows and rainfall in mountain and urban area. Several GIS and CAD data were used for the preparation of shape model and an automatic mesh generation method based on Delaunay method was developed. The present method is shown to be a useful planning and design tool for the natural disasters and the change of environments.