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Bunkyo-ku, Japan

Iribe T.,University of Ryukyus | Fujisawa T.,Prometech Software Inc. | Koshizuka S.,University of Tokyo
Coastal Engineering Journal | Year: 2010

Methods for reduction in communication time during parallel computation of a particle method for flow simulation of seaside areas are presented. Since the analysis region was divided for parallel computation using a PC cluster, communications among processors were necessary. Two techniques were tested. The first was renumbering, which reduced the amount of communication. The second was the use of a communication list including the maximum and minimum particle numbers. These techniques improved communication speed. Performance during large-scale simulation was examined by computing tsunami wave run-up on a seaside area using 6,300,000 particles. A calculation time of 237 hr was used to generate real time data for 60 s. © 2010 World Scientific Publishing Company and Japan Society of Civil Engineers. Source

Murotani K.,University of Tokyo | Oochi M.,University of Tokyo | Fujisawa T.,Prometech Software Inc. | Koshizuka S.,University of Tokyo | Yoshimura S.,University of Tokyo
Transactions of the Japan Society for Computational Engineering and Science | Year: 2012

In this research, a new distributed memory parallel algorithm of the explicit MPS (Moving Particle Simulation) method is presented. The analysis region is divided for a distributed memory parallel computation using ParMETIS. Two communication techniques of an overlapping method and a non-overlapping method are estimated by parallel scalability tests. Since we find that load balance is most important for the distributed memory parallel algorithm of the explicit MPS method, we find that the non-overlapping method is more effective than the overlapping method. As a result, we have been able to do the MPS analysis of 268 million particles in 38 seconds per one time step. Performance during large scale simulation is examined by computing tsunami wave run-up on a virtual gulf area using up to 58 million particles. © 2012 by the Japan Society for Computational Engineering and Science. Source

Okukubo K.,Toppan Printing Co. | Yagi K.,Toppan Printing Co. | Yoshino K.,Toppan Printing Co. | Watanabe T.,Toppan Printing Co. | And 4 more authors.
ACM SIGGRAPH 2012 Posters, SIGGRAPH'12 | Year: 2012

ViewPaint is a viewing system for paintings. This system was produced to propose a new exhibition method using digital technology to art museums. In developing this system, we have tried to realize the idea that if viewers can explore a painting converted into a three-dimensional space, it is possible to foster understanding and imagination, with viewers considering why artists chose certain compositions, what motifs are depicted, and what the background to the period was. © 2012 ACM. Source

Shibata K.,University of Tokyo | Koshizuka S.,University of Tokyo | Masaie I.,Prometech Software Inc.
Computer Methods in Applied Mechanics and Engineering | Year: 2016

We developed an ellipsoidal particle model to reduce the number of particles and the computational costs of the moving particle semi-implicit (MPS) method. A coordinate transformation was conducted to treat ellipsoidal particles in the same manner as sphere particles. The model for the MPS method's Laplacian operator was extended for use with ellipsoidal particles. The developed method is effective in cases where the rate of change of a physical quantity or shape in any given direction is smaller than that in other directions, and the authors have applied it to dam breaking problems in both two and three dimensions. As a result, the developed method's ability to reduce the required number of particles and the computational costs of particle simulations has been confirmed. The developed ellipsoidal particle model was also applied to smoothed particle hydrodynamics. © 2016. Source

Ui A.,Japan Nuclear Energy Safety Organization | Ebata S.,Japan Nuclear Energy Safety Organization | Kasahara F.,Japan Nuclear Energy Safety Organization | Iribe T.,Prometech Software Inc. | And 2 more authors.
Journal of Nuclear Science and Technology | Year: 2010

It has been a concern that sump screen clogging would occur in pressurized water reactors (PWRs) in the case of a loss-of-coolant accident (LOCA), because two-phase jet flow would strip off thermal insulation from the piping and wash down the broken and fragmented debris to sump screens. It is necessary for the evaluation of the effectiveness of sump screens to estimate the amount of transported debris from a break position to sumps. In general, conservative logic trees have been used to determine debris transport rates. Realistic debris transport evaluation is useful for considering measures and rational decision making in licensing. The purpose of this study is to develop a debris transport evaluation model and to apply the model to this issue. We developed a solid-liquid multiphase model that is capable of simulating debris transport, settling, and resuspension. The model is able to treat solid particles of different sizes, which are smaller than uniform-sized liquid particles. This approach contributes to reducing the calculation cost in a large-scale simulation. The model and a turbulence model were implemented into a code based on the moving particle semi-implicit (MPS) method. Several open-channel hydraulic experiments with fibrous debris were conducted. The code named SANSUI 2.0 was validated by the comparison of the analytical results with experiments. This method was applied to the debris transport analysis of a full-scale PWR containment vessel floor, and the debris transport behavior was evaluated. © Atomic Energy Society of Japan. Source

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