Bubble flow analysis using multi-phase field method

Sugihara, Kenta; Onodera, Naoyuki; Sitompul, Y.; Idomura, Yasuhiro; Yamashita, Susumu

EPJ Web of Conferences, 302, p.03002_1 - 03002_10, 2024/10

https://doi.org/10.1051/epjconf/202430203002

In simulations of gas-liquid two-phase flows using conventional interface capture methods, we observed that when bubbles come close to each other, they tend to merge numerically, despite experimental evidence indicating that they would repel each other. Given the significant impact of sequential numerical coalescence on flow patterns, it is necessary to regulate the merging behavior of close bubbles. To address this issue, we introduced the Multi- Phase Field (MPF) method, which mitigates bubble coalescence by applying an independent fluid fraction function to each bubble. In this study, we employed the MPF based on the N-phase model to minimize numerical errors associated with surface interactions at triple junction points. Additionally, we implemented the Ordered Active Parameter Tracking (OAPT) method to efficiently store several hundreds of fluid fraction functions. To validate the MPF method, we conducted analysis of turbulent bubbly pipe flows and compared the results against experimental data from Colin et al. The validation results showed reasonable agreements with respect to the bubble distribution and the flow velocity profiles.

Atomic position and the chemical state of an active Sn dopant for Sn-doped -GaO(001)

Tsai, Y. H.*; Kobata, Masaaki; Fukuda, Tatsuo; Tanida, Hajime; Kobayashi, Toru; Yamashita, Yoshiyuki*

Applied Physics Letters, 124(11), p.112105_1 - 112105_5, 2024/03

https://doi.org/10.1063/5.0198160

Deep learning approach for an interface structure analysis with a large statistical noise in neutron reflectometry

Aoki, Hiroyuki; Liu, Y.*; Yamashita, Takashi*

Scientific Reports (Internet), 11, p.22711_1 - 22711_9, 2021/11

https://doi.org/10.1038/s41598-021-02085-6

The International Atomic Energy Agency Nuclear Energy Management School 2012

Ohgama, Kazuya; Ando, Yoko; Yamaguchi, Mika; Ikuta, Yuko; Shinohara, Nobuo; Murakami, Hiroyuki; Yamashita, Kiyonobu; Uesaka, Mitsuru*; Demachi, Kazuyuki*; Komiyama, Ryoichi*; et al.

JAEA-Review 2013-004, 76 Pages, 2013/05

JAEA-Review-2013-004.pdf:13.53MB

JAEA together with the Japan Nuclear Human Resource Development Network (JN-HRD Net), the University of Tokyo (UT) and the Japan Atomic Industrial Forum (JAIF) cohosted the IAEA-Nuclear Energy Management School in Tokai Village, aiming that Japan will be the center of nuclear HRD in the Asian region. In the school, not only lectures by IAEA experts, but also lectures by Japanese experts and technical visits were included for foreign participants. The school contributed to the internationalization of Japanese young professionals, development of nuclear human resource of other countries, and enhancement of cooperation between IAEA and Japan. Additionally, collaborative relationship within JN-HRD Net was strengthened by the school. In this report, findings obtained during the preparatory work and the school period are reported for future international nuclear HRD activities in Japan.

Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

Yan, Y.*; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Hata, Kuniki; Meesungnoen, J.*; Jay-Gerin, J.-P.*

Canadian Journal of Chemistry, 88(10), p.1026 - 1033, 2010/10

https://doi.org/10.1139/V10-120

The optical absorption spectra of the solvated electron (e) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220-270 C. Over the density range studied (0.45-0.59 g/cm), the position of the absorption maximum () of e is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, decreases monotonically with increasing temperature in passing through the phase transition at (239.5 C). By contrast, at a fixed density, exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and supercritical regimes.

Development of a SH wave single unit electromagnetic acoustic transducer (EMAT) for MONJU reactor vessel in-service inspection

Xu, Y.*; Tagawa, Akihiro; Fujiki, Kazunari*; Ueda, Masashi; Yamashita, Takuya

Proceedings of the 17th International Conference on Nuclear Engineering (ICONE-17) (CD-ROM), 9 Pages, 2009/07

In-service inspection is carried out to confirm the integrity of the main components of "MONJU". The ambient temperature during the inspection is 200 C and the irradiation field is 10 Gy/hr. A Periodic Permanent Magnet (PPM) structure has been used for electromagnetic acoustic transducer (EMAT). The PPM structure is the structure of putting in order alternately the S pole and N pole laterally magnetized magnets. A Halbach magnet structure is the structure which sandwiched the longitudinally magnetized magnets between each magnet of PPM structure. Thereby, magnetic flux density is improved 1.4 times. Moreover, it also checked aiming at 4 times as many improvement in detection sensitivity as this by a new signal processing method. The high temperature characteristic and high temperature durability of Halbach type EMAT in 200 hours which corresponds the twice of inspection time under the 200 C inspection environment are reported.

Design analysis for reducing dose rate in the NBI to realize direct access by workers for a fusion experimental reactor

Inoue, Takashi; ; ; Yamashita, Y.*

Fusion Technology 1996, 0, p.1799 - 1802, 1996/00

no abstracts in English

Neutronics of neutral beam injector for ITER; Japanese proposal

Inoue, Takashi; Akiba, Masato; Araki, Masanori; Hanada, Masaya; ; Mizuno, Makoto; Okumura, Yoshikazu; Ohara, Yoshihiro; Seki, Masahiro; Tanaka, Shigeru; et al.

Fusion Engineering and Design, 18, p.369 - 376, 1991/00

https://doi.org/10.1016/0920-3796(91)90153-H

no abstracts in English

A Pulse radiolysis study on the temperature dependent absorption spectra of Br and Br in aqueous solutions

Lin, M.; Katsumura, Yosuke; Muroya, Yusa*; Fu, H.*; Yan, Y.*; Yamashita, Shinichi; Mostafavi, M.*

no journal, , 

The absorption spectra of Br and Br in aqueous solutions are investigated by pulse radiolysis techniques from room temperature to 380 and 350 C, respectively. Temperature dependent spectrum of Br is also measured under steady-sate. If the absorption of Br is of Charge Transfer To Solvent (CTTS), those of Br and Br are not.

A Study on the reaction mechanisms of edaravone and its derivatives

Hata, Kuniki; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Yamashita, Shinichi; Fu, H. Y.*; Kudo, Hisaaki*; Nakagawa, Keiichi*; Nakagawa, Hidehiko*

no journal, , 

In order to investigate the reaction mechanism of edaravone (3-methyl-1-phenyl-2-pyrazolin- 5-one) with OH, the reactivity of edaravone derivatives which have different substituent from edaravone was observed by pulse radiolysis system. From the experiments, OH-adduct radical formed by the addition of OH to phenyl group has been identified as a main intermediate.