Free-surface flow simulations with floating objects using lattice Boltzmann method

Watanabe, Seiya*; Kawahara, Jun*; Aoki, Takayuki*; Sugihara, Kenta; Takase, Shinsuke*; Moriguchi, Shuji*; Hashimoto, Hirotada*

Engineering Applications of Computational Fluid Mechanics, 17(1), p.2211143_1 - 2211143_23, 2023/00

https://doi.org/10.1080/19942060.2023.2211143

In tsunami inundations or slope disasters of heavy rain, a lot of floating debris or driftwood logs are included in the flows. The damage to structures from solid body impacts is more severe than the damage from the water pressure. In order to study free-surface flows that include floating debris, developing a high-accurate simulation code of free-surface flows with high performance for large-scale computations is desired. We propose the single-phase free-surface flow model based on the cumulant lattice Boltzmann method coupled with a particle-based rigid body simulation. The discrete element method calculates the contact interaction between solids. An octree-based AMR (Adaptive Mesh Refinement) method is introduced to improve computational accuracy and time-to-solution. High-resolution grids are assigned near the free surfaces and solid boundaries. We conducted two kinds of tsunami flow experiments in the 15 and 70 m water tanks at Hachinohe Institute of Technology and Kobe University to validate the accuracy of the proposed model. The simulation results have shown good agreement with the experiments for the drifting speed, the number of trapped wood pieces, and the stacked angles.

Tree cutting approach for domain partitioning on forest-of-octrees-based block-structured static adaptive mesh refinement with lattice Boltzmann method

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

Parallel Computing, 108, p.102851_1 - 102851_12, 2021/12

https://doi.org/10.1016/j.parco.2021.102851

The aerodynamics simulation code based on the lattice Boltzmann method (LBM) using forest-of-octrees-based block-structured local mesh refinement (LMR) was implemented, and its performance was evaluated on GPU-based supercomputers. We found that the conventional Space-Filling-Curve-based (SFC) domain partitioning algorithm results in costly halo communication in our aerodynamics simulations. Our new tree cutting approach improved the locality and the topology of the partitioned sub-domains and reduced the communication cost to one-third or one-fourth of the original SFC approach. In the strong scaling test, the code achieved maximum speedup at the performance of 2207 MLUPS (mega- lattice update per second) on 128 GPUs. In the weak scaling test, the code achieved 9620 MLUPS at 128 GPUs with 4.473 billion grid points, while the parallel efficiency was 93.4% from 8 to 128 GPUs.

Numerical analysis of interfacial growth and deformation in horizontal stratified two-phase flow by lattice Boltzmann method

Ebihara, Kenichi

JAERI-Research 2005-004, 121 Pages, 2005/03

JAERI-Research-2005-004.pdf:19.79MB

This report is the JAERI's report version of the doctor thesis by the author. In this report, first, the validity and usefulness of the application of the two-phase fluid model of the lattice-gas method and the lattice Boltzmann method(LBM) are examined. On the basis of the examination, next, the horizontal stratified two-phase flow that is the fundamental and important flow is simulated by the HCZ model which is one of the two-phase fluid model of the LBM. It is seen that the interfacial growth of the HCZ model satisfies the Kelvin-Helmholtz instability theory and reproduces the theoretical two-phase flow regime map of Taitel and Dukler(T-D map). It is found that more superficial flow velocity of the rare phase is necessary in the channel with the narrow width. The HCZ model can also simulate the droplet generation accompanying more complex interfacial phenomena and reproduce the experimental correlation of Ishii and Grolmes in the range of the distribution of the experimental data.

Study on interfacial growth and deformation of horizontal stratified two-phase flow by lattice Boltzmann method

Ebihara, Kenichi

Tsukuba Daigaku Daigakuin Shisutemu Joho Kogaku Kenkyuka Hakase Gakui Rombun, 134 Pages, 2004/09

In this thesis, first the liquid-gas models of the lattice method are examined by applying them to two-phase flow simulations. Next the liquid-gas model(the HCZ model) of the lattice Boltzmann method is applied to the three-dimensional simulation of the horizontal stratified two-phase flow. The following results are obtained. (1)The two- and three- dimensional interface simulated by the HCZ model satisfies the Kelvin-Helmholtz instability theory. (2)In the simulation of the interfacial growth in the rectangular channel, it is found that the relation between the interfacial growth and the flow state is in agreement with the flow regime map proposed theoretically by Taitel and Dukler. (3)It is also found that the three dimensionality becomes remarkable and the interfacial growth needs more flow rate of the rare phase than that of the theoretical flow regime map when the channel width is narrower. (4)In the droplet creation simulation, it is found that the relation between the droplet creation and the flow state simulates the experimental correlation proposed by Ishii and Grolmes.

Evaluation of influence of pipe width on interfacial growth of horizontal stratified two-phase flow in rectangular pipe by lattice Boltzmann method

Ebihara, Kenichi; Watanabe, Tadashi

Nihon Kikai Gakkai Rombunshu, B, 70(694), p.1393 - 1399, 2004/06

https://doi.org/10.1299/kikaib.70.1393

The horizontal stratified two-phase flow in the rectangular pipe whose width in smaller than the height is simulated by the one-component two-phase lattice Boltzmann method. The interfacial growth between two phases is measured for three cases with the different pipe width and the measured dimensionless number charactering the two-phase flow is compared with the flow regime map proposed by Taitel and Dukler. It is found that the boundary separating the interfacical growth from the non-growth which is obtained by the simulations is larger in the flow regime map when the pipe width is narrower.

Numerical simulation of bubbly two-phase flow using the lattice Boltzmann method

Watanabe, Tadashi; Ebihara, Kenichi

Proceedings of 4th International Conference on Supercomputing in Nuclear Applications (SNA 2000) (CD-ROM), 10 Pages, 2000/09

no abstracts in English

Parallelization of Lattice Boltzmann codes

; Yokokawa, Mitsuo;

Keisan Kogaku Koenkai Rombunshu, 1(1), p.101 - 104, 1996/05

no abstracts in English

Development of analytical model for evaluating temperature fructuation in coolant(VIII); Development of a Monte Carlo direct simulation code THEMIS

PNC TN9410 94-111, 42 Pages, 1994/04

PNC-TN9410-94-111.pdf:1.55MB

Thermal striping phenomena are characterized by stationaly random temperature fluctuations and observed in the region immediately above the core exit of LMFBRs due to the interactions of cold and hot sodium. To evaluate the phenomena, it is neccessary to consider a time-dependent heat transfer coefficient to structures from fluid, in the same manner as a evaluation of a stationaly temperature fluctuation in fluid. For this purpose, a computer program THEMIS (Time-dependent Heat transfer Evaluation by Monte Carlo Direct Simulation) has been developed for the thermohydraulic analysis based on the Boltzmann equation. A two-dimensional duct flow problem has been solved to check the fundamental performance of the THEMIS code. The main results are as follows: (1)Axial distribution of molecular velocity U has shown good agreement with the solution of the Navier-Stokes equation under the condition of Kn=0.0002. (2)An acceleration on the VP-2600 vector processor is about 12 times as the VP-2600 scalar processor. Future works of the THEMIS code development are (1)investigation of the applicabilities in a non-isothermal fluid system and in a complex geometry system and (2)verification with detailed experimental results.

Vectorization of the rarefied gas flow analysis code using the direct simulation Monte Carlo method

Watanabe, Kenji*; Yokokawa, Mitsuo; ;

JAERI-M 90-192, 32 Pages, 1990/11

JAERI-M-90-192.pdf:0.78MB

no abstracts in English

Reaction of molybdenum and molybdenum-base alloy with sintered LiO pellets

; Kurasawa, T.; ; ; ;

Journal of Nuclear Materials, 80(2), p.249 - 252, 1979/00

https://doi.org/10.1016/0022-3115(79)90187-9

no abstracts in English