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Journal Articles

Improved domain partitioning on tree-based mesh-refined lattice Boltzmann method

Hasegawa, Yuta; Aoki, Takayuki*; Kobayashi, Hiromichi*; Idomura, Yasuhiro; Onodera, Naoyuki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 6 Pages, 2021/05

We introduce an improved domain partitioning method called "tree cutting approach" for the aerodynamics simulation code based on the lattice Boltzmann method (LBM) with the forest-of-octrees-based local mesh refinement (LMR). The conventional domain partitioning algorithm based on the space-filling curve (SFC), which is widely used in LMR, caused a costly halo data communication which became a bottleneck of our aerodynamics simulation on the GPU-based supercomputers. Our tree cutting approach adopts a hybrid domain partitioning with the coarse structured block decomposition and the SFC partitioning in each block. This hybrid approach improved the locality and the topology of the partitioned sub-domains and reduced the amount of the halo communication to one-third of the original SFC approach. The code achieved $$times 1.23$$ speedup on 8 GPUs, and achieved $$times 1.82$$ speedup at the performance of 2207 MLUPS (mega-lattice update per second) on 128 GPUs with strong scaling test.

Journal Articles

The Examination of advanced analysis method on unsteady gas entrainment vortex applying AMR method

Matsushita, Kentaro; Fujisaki, Tatsuya*; Ezure, Toshiki; Tanaka, Masaaki; Uchida, Mao*; Sakai, Takaaki*

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 6 Pages, 2021/05

For the gas entrainment vortex at the free surface in sodium-cooled fast reactors, development of the numerical analysis method to evaluate amount of the gas entrainment from the free surface has been developing. In this paper, the automatic creation of analysis meshes which can suppress the calculation cost while maintaining the prediction accuracy of the vortex shape is investigated, and the adaptive mesh refinement (AMR) method is examined to the creation of analysis mesh applying to the unsteady vortex system. The refined mesh based on the criterion evaluated by vorticity, Q-value as second invariant of the velocity and the discriminant for the eigen equation of the velocity gradient tensor is considered, and it found that the AMR method based on Q-value can refine the analysis meshes most efficiently.

Journal Articles

Development of neutronics, thermal-hydraulics, and structure mechanics coupled analysis method on integrated numerical analysis for design optimization support in fast reactor

Doda, Norihiro; Uwaba, Tomoyuki; Nemoto, Toshiyuki*; Yokoyama, Kenji; Tanaka, Masaaki

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 4 Pages, 2021/05

For design optimization of fast reactors, in order to consider the feedback reactivity due to thermal deformation of the core when the core temperature rises, which could not be considered in the conventional design analysis, a neutronics, thermal-hydraulics, and structure mechanics coupled analysis method has been developed. Neutronics code, plant dynamics code, and structural mechanics code are coupled by a control module in python script. This paper outlines the coupling method of analysis codes and the results of its application to an experiment in an actual plant.

Journal Articles

Acceleration of locally mesh allocated Poisson solver using mixed precision

Onodera, Naoyuki; Idomura, Yasuhiro; Hasegawa, Yuta; Shimokawabe, Takashi*; Aoki, Takayuki*

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 3 Pages, 2021/05

We develop a mixed-precision preconditioner for the pressure Poisson equation in a two-phase flow CFD code JUPITER-AMR. The multi-grid (MG) preconditioner is constructed based on the geometric MG method with a three- stage V-cycle, and a cache-reuse SOR (CR-SOR) method at each stage. The numerical experiments are conducted for two-phase flows in a fuel bundle of a nuclear reactor. The MG-CG solver in single-precision shows the same convergence histories as double-precision, which is about 75% of the computational time in double-precision. In the strong scaling test, the MG-CG solver in single-precision is accelerated by 1.88 times between 32 and 96 GPUs.

Journal Articles

Multi-resolution steady flow prediction with convolutional neural networks

Asahi, Yuichi; Hatayama, Sora*; Shimokawabe, Takashi*; Onodera, Naoyuki; Hasegawa, Yuta; Idomura, Yasuhiro

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 26, 4 Pages, 2021/05

We develop a convolutional neural network model to predict the multi-resolution steady flow. Based on the state-of-the-art image-to-image translation model Pix2PixHD, our model can predict the high resolution flow field from the signed distance function. By patching the high resolution data, the memory requirements in our model is suppressed compared to Pix2PixHD.

Journal Articles

Effective usage of multiphysics calculation for crevice corrosion

Yamamoto, Masahiro

Keisan Kogaku, 25(3), p.4105 - 4108, 2020/07

Recently, some attempts using Multi-Physics simulation for corrosion problems, especially crevice corrosion, have been increasing. Corrosion undergoes by electrochemical reaction. The numerical calculation procedure is used a non-liner equation. Furthermore, this reaction is affected by environmental factors, i.e. composition, amount and mobility of chemical species and redox potential. These values change with time by corrosion process itself. This report, these needs for Multi-Physics calculations are introduced.

Journal Articles

Ensemble wind simulation using a mesh-refined lattice Boltzmann method

Hasegawa, Yuta; Onodera, Naoyuki; Idomura, Yasuhiro

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 25, 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.

Journal Articles

GPU-acceleration of locally mesh allocated Poisson solver

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

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 25, 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 $$times$$3 speed up is achieved with strong scaling test from 8 to 216 GPUs on TSUBAME 3.0.

Journal Articles

Development of neutronics and thermal-hydraulics coupled analysis method on platform for design optimization in fast reactor

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

Keisan Kogaku Koenkai Rombunshu (CD-ROM), 25, 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.

Journal Articles

Application of data assimilation in groundwater hydrology; Characterization of hydraulic heterogeneity of hydrogeological structure based on in-situ data

Onoe, Hironori

Keisan Kogaku, 24(1), p.3851 - 3854, 2019/01

In this study, inverse analysis using observed data of pumping test was carried for confirmation of the applicability of inverse analysis method of groundwater flow based on in-situ data. Target of this inverse analysis was spatial distribution of hydrogeological heterogeneity of the fault. Inverse analysis had been applied to the area around the Mizunami Underground Research Laboratory, which is constructed by the Japan Atomic Energy Agency in order to construct scientific and technological basis for geological disposal of High-level Radioactive Waste. As a result of this study, the estimated results of inverse analysis are consistent with previous study result, and it was concluded that inverse analysis using hydraulic response due to pumping test is effective for hydrogeological characterization in deep underground.

Journal Articles

The Mizunami Underground Research Laboratory

Onoe, Hironori

Keisan Kogaku, 23(2), p.3751 - 3752, 2018/04

In this paper, outline and current status of Mizunami Underground Research Laboratory, which is constructed by Tono Geoscience Center of Japan Atomic Energy Agency, in the Mizunami city, Gifu is introduced.

Journal Articles

Development of V2UP (Verification & Validation plus Uncertainty quantification and Prediction) procedure for high cycle thermal fatigue in fast reactor; A Challenge to implementation of quality management

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".

Journal Articles

An Illustration by the next generation numerical simulator for quake-proofing on the K

Nakajima, Norihiro; Suzuki, Yoshio; Miyamura, Hiroko; Nishida, Akemi; Kawakami, Yoshiaki; Guo, Z.; Tomiyama, Eiji*

Keisan Kogaku, 20(4), p.3338 - 3340, 2015/12

The issue 5 in the field 4 of "Monodukuri" in the HPCI strategy project is introduced. The title of the issue 5 is "research and development for the next-generation earthquake-resistant simulation of the large plants such as nuclear energy facilities". The illustration intends for a high temperature engineering examination research reactor. Implementation of FIESTA (Finite Element Analysis for Structure of Assembly) on K is described by reporting its efficiency and performance. To show a result of the numerical analysis, a visualization technique for the big data was described.

Journal Articles

Open-source remote visualization software PBVR

Kawamura, Takuma

Keisan Kogaku Nabi, Nyusu Reta (Internet), 7, p.4 - 5, 2015/06

It has been difficult for traditional remote visualization systems to explore large-scale data because of bottlenecks such as visualization speed, memory limit, and data transfer time. Remote visualization software PBVR (Particle-Based Volume Rendering) employed client-server system and achieved interactive data exploration by converting the large-scale data to small particle data which is transferred to the client machine. We developed PBVR system as open source code and contributed an article about PBVR system.

Journal Articles

R&D of verification & validation for seismic simulation of nuclear plant

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.

Journal Articles

R&D of validity evaluation system for seismic simulation of nuclear power plant

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.

Journal Articles

Preliminary study on the finite element analysis for solid mechanics on K computer

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.

Journal Articles

R&D of atomic energy grid infrastructure AEGIS

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.

Journal Articles

Performance evaluation of structural analysis solver for many RHS problem on multicore processor

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.

Journal Articles

Preliminary study on a matrix-coupling framework for huge assembled structures

Yamada, Tomonori

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

no abstracts in English

77 (Records 1-20 displayed on this page)