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Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro

Dai-25-Kai Nippon Keisan Kogaku Koenkai Rombunshu (CD-ROM), 4 Pages, 2020/06

We developed a GPU-based CFD code using a mesh-refined lattice Boltzmann method (LBM), which enables ensemble simulations for wind and plume dispersion in urban cities. The code is tuned for Pascal or Volta GPU architectures, and is able to perform real-time wind simulations with several kilometers square region and several meters of grid resolution. We examined the developed code against the field experiment JU2003 in Oklahoma City. In the comparison, wind conditions showed good agreements, and the ensemble-averaged and maximum values of tracer concentration satisfied the factor 2 agreements.

Onodera, Naoyuki; Idomura, Yasuhiro; Ali, Y.*; Shimokawabe, Takashi*; Aoki, Takayuki*

Dai-25-Kai Nippon Keisan Kogaku Koenkai Rombunshu (CD-ROM), 4 Pages, 2020/06

We have developed the stencil-based CFD code JUPITER for simulating three-dimensional multiphase flows. A GPU-accelerated Poisson solver based on the preconditioned conjugate gradient (P-CG) method with a multigrid preconditioner was developed for the JUPITER with block-structured AMR mesh. All Poisson kernels were implemented using CUDA, and the GPU kernel function is well tuned to achieve high performance on GPU supercomputers. The developed multigrid solver shows good convergence of about 1/7 compared with the original P-CG method, and 3 speed up is achieved with strong scaling test from 8 to 216 GPUs on TSUBAME 3.0.

Doda, Norihiro; Hamase, Erina; Yokoyama, Kenji; Tanaka, Masaaki

Dai-25-Kai Nippon Keisan Kogaku Koenkai Rombunshu (CD-ROM), 4 Pages, 2020/06

With the aim of advancing the design optimization in fast reactors, neutronics and thermal-hydraulics coupled analysis method which can consider the temporal change of neutron flux distribution in the core has been developed. A three-dimensional neutronics analysis code and a plant dynamics analysis code are coupled on a platform using Python programing. In this report, outlines of the coupling method of analysis codes, the results of its application to the actual plant under a virtual accidental condition, and the future development is described.

Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 22, 4 Pages, 2017/05

In the development of the simulation code and the numerical estimation for high cycle thermal fatigue on a structure caused by thermal striping phenomena in sodium cooled fast reactors, implementation of verification and validation (V&V) process is indispensable. A procedure named V2UP (Verification and Validation plus Uncertainty quantification and Prediction) has been made by referring to the existing guidelines regarding the V&V and the methodologies of the safety assessment. In this paper, a challenging installation of quality management procedures into the V2UP procedure is attempted based on the JSCES Standard for "A Model Procedure for Engineering Simulation".

Suzuki, Yoshio; Nishida, Akemi; Uzawa, Ken; Nakajima, Norihiro

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 17, 4 Pages, 2012/05

Our goal is to evaluate the validity of results obtained from seismic simulation of entire nuclear plant, and then to estimate real behavior. In this study, we have established a trial tool to enable a zooming analysis from a combining analysis of ground-building-equipments (beam model) to an assembly structural analysis of equipments (solid model) in order to compare results of beam model and solid model. By applying the tool to analysis of a cantilever model with various cross sections, we have confirmed that results of solid model well coincide with theoretical solutions and results of beam model.

Suzuki, Yoshio; Miyamura, Hiroko

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 16, 4 Pages, 2011/05

Our goal is to evaluate the validity of results obtained from seismic simulation of entire nuclear power plant, and then to estimate real phenomena. In this study, we have established a trial system to evaluate the validity by automatically abstracting a characteristic spatial profile of physical values in consideration of uncertainty caused by discretization, as one of methods to reveal factors of various uncertainties included in the simulation. By applying the system to a seismic simulation, we have confirmed that various characteristic spatial profiles of stress with error estimation are automatically classified and abstracted from the simulation result.

Yamada, Tomonori

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 16, 2 Pages, 2011/05

The Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) has been developing the next-generation supercomputer, which has capability of ten peta floating point operations per second, and will install it at Kobe city. As an application of macro-scale solid mechanics, Japan Atomic Energy Agency and his colleagues proposed a research activity on K entitled "next generation seismic analysis of large plants in its entirety" in Monodukuri field. In this paper, a preliminary study on the finite element analysis for solid mechanics on K is described.

Suzuki, Yoshio; Tatekawa, Takayuki; Kim, G.; Kino, Chiaki; Miyamura, Hiroko; Teshima, Naoya; Hayashi, Sachiko*; Aoyagi, Tetsuo; Takemiya, Hiroshi; Nakajima, Norihiro

Keisan Kogaku Koenkai Rombunshu, 15(2), p.1051 - 1054, 2010/05

We have developed the Atomic Energy Grid InfraStructure (AEGIS) for establishing computational infrastructure for nuclear field. In this R&D we have inherited the knowledge and skills in ITBL Infrastructure developed in the national project ITBL (Information Technology Based Laboratory), which aims at establishment of virtual research environment where supercomputers and data bases are connected by network. Here we have focused on two issues: improvements of safety and usability. For the safety, we have made the authentication mechanism double with both the personal certification and the machine certification. For the usability, we have developed the grid-enabled client API to use grid functions on a user terminal. By those R&Ds, we have successfully contributed to various nuclear researches, such as "full scale 3D vibration simulator for an entire nuclear power plant", "simulation for predicting quake-proof capability of nuclear power plants", and so on.

Yamada, Tomonori; Kawai, Hiroshi*

Keisan Kogaku Koenkai Rombunshu, 15(1), p.179 - 180, 2010/05

In this study, computational performance of iterative solver of large linear equations with many right hand side vectors derived from finite element discretization in structural mechanics is evaluated. The current multicore architecture has memory wall problem and many iterative solvers suffer for this problem. Hence, high performance computing with iterative solver on multicore architecture is one of key issues in recent computer science. Because the performance of sparse matrix single vector multiplication has well surveyed, the performance of sparse matrix multiple vectors multiplication is investigated in this paper.

Yamada, Tomonori

Keisan Kogaku Koenkai Rombunshu, 14(1), p.247 - 248, 2009/05

no abstracts in English

Miyamura, Tomoshi*; Arai, Kentaro*; Mimura, Yasunari*; Yoshimura, Shinobu*; Suzuki, Yoshio

Keisan Kogaku Koenkai Rombunshu, 12(2), p.655 - 658, 2007/05

ADVENTURE_Opt is one of the software modules in the ADVENTURE System, which is an open source software system for computational mechanics. The system is designed for conducting large-scale analysis and design. ADVENTURE_Opt can conduct optimization of artifacts using an optimization algorithm such as the Real coded GA, and the finite element analyses are conducted for evaluating an objective function. In this paper, the ADVENTURE_Opt is modified for using the ITBL environment, which is a grid-environment developed in the national project in Japan. In the computation using the ADVENTURE_Opt, conducting the finite element analyses is the most time consuming. In the present implementation, this computation is conducted in the ITBL environment and the other parts are conducted on a personal computer. The ITBL client API library is used for implementing the system.

Ida, Masato; Oshima, Nobuyuki*

Keisan Kogaku Koenkai Rombunshu, 11(1), p.263 - 264, 2006/06

no abstracts in English

Shinohara, Kazunori; Okuda, Hiroshi*; Ito, Satoshi*; Nakajima, Norihiro; Ida, Masato

Keisan Kogaku Koenkai Rombunshu, 10(2), p.629 - 632, 2005/05

To obtain optimal designed shape effectively, a parallel computing method of determining Armijo's line-search step size of the adjoint variable method is proposed. The adjoint valiable method is based on the Lagrange multiplier method (a conditional variational principle), and consists of the state equation, the adjoint equation and the sensitivity equation. The equations for decreasing the fluid drag of shaped surface under a constant volume condition are formulated. To solve the equations effectively by the steepest descent method, the parallel algorithm that finds the Armijo's line-search step size is implemented by using ITBL (the grid system of Japan's shared super computers attached to the network). Using this parallel method, the calculation cost can be reduced.

Tian, R.; Nakajima, Norihiro; Yagawa, Genki

Keisan Kogaku Koenkai Rombunshu, 10(1), p.393 - 396, 2005/05

A known problem of partition of unity-based generalized finite element methods (referred to as GFEM) is the linear dependence problem, which leads to singular global (stiffness) matrices. Thus far, attempts to eliminate the linear dependence problem have been unsuccessful. Numerical experiments are carried out among several GFEMs to investigate the problem. Based on the numerical experiments, simple but effective approaches to eliminating the linear dependence problem are suggested.

Tian, R.; Nakajima, Norihiro; Yagawa, Genki

Keisan Kogaku Koenkai Rombunshu, 10(1), p.397 - 400, 2005/05

An attempt is made to treat boundary conditions in EFGM through only nodal arrangements. One of major merits of the proposed nodal arrangement scheme is its straightforwardness in implementation. The accuracy of this nodal arrangement boundary treatment and its influence on convergence are assessed by comparing with the Lagrange multiplier and penalty methods using one- and two- dimensional problems. The nodal arrangement scheme shows a same performance as the Lagrange multiplier and penalty methods in the one-dimensional tests, but it evidently outperforms the penalty method in the two-dimensional tests.

Hazama, Osamu; Nakajima, Norihiro

Keisan Kogaku Koenkai Rombunshu, 10(1), p.259 - 260, 2005/05

It is impossible to carry out a controlled laboratory experiments on an operational full-scale power plant. Therefore, construction of a testbed to assess the safety of such systems by numerical means is believed to be meaningful. At CCSE/JAERI, a project to develop a numerical testbed to assess the safety of nuclear reactors have been begun. Simulations of such complex systems will inevitably require tremendous amount of computational resources. Therefore, the numerical testbed is constructed on the ITBL Grid middleware. A prototype of a generic software coupling interface was developed to couple various simulation software within the ITBL Grid environment to execute large-scale multi-disciplinary simulations on the testbed. This coupler and its application to some fluid-structure problems will be illustrated.

Suzuki, Yoshio; Matsumoto, Nobuko*; Sai, Kazunori*; Yamagishi, Nobuhiro*

Keisan Kogaku Koenkai Rombunshu, 9(2), p.613 - 616, 2004/05

no abstracts in English

Hazama, Osamu; Guo, Z.*

Keisan Kogaku Koenkai Rombunshu, 9(2), p.617 - 620, 2004/05

Although multi-disciplinary coupled simulations are considered important and necessary by many to reflect reality into the numerical simulations, there still exist many obstacles which inhibit such numerical simulations. There still exist very few software packages in the market which satisfy user needs in such numerical simulations. In many instances, self-development of software packages which allow for such coupled simulations will also be quite burdensome simply because considering multi-physics require more knowledge, experience, time . Parallel processing of the simulations will definitely be required to aquire meaningful coupled solutions within a given practical time. Under the international collaborative efforts between CCSE/JAERI and Fraunhofer SCAI, a generic code coupling mechanism and implementation are developed for multi-disciplinary simulation of continua in a meta-computing environment. Two libraries, STAMPI, by CCSE/JAERI, and MpCCI, by Fraunhofer SCAI, will be implemented together to allow such simulations.

Sai, Kazunori*; Suzuki, Yoshio; Araki, Fumiaki*; Uehara, Hitoshi*; Haginoya, Hirofumi*

Keisan Kogaku Koenkai Rombunshu, 8(2), p.761 - 764, 2003/05

no abstracts in English

Imamura, Toshiyuki; Hasegawa, Yukihiro*; Yamagishi, Nobuhiro*; Takemiya, Hiroshi*

Keisan Kogaku Koenkai Rombunshu, 8(2), p.793 - 796, 2003/05

no abstracts in English