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Journal Articles

Evaluation of gas entrainment flow rate by free surface vortex

Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro; Ezure, Toshiki; Tanaka, Masaaki

Konsoryu, 36(1), p.63 - 69, 2022/03

On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, entrained gas flow rate a simple gas entrainment experiment is conducted with focusing on effect of pressure difference between upper and lower tanks. Pressure difference between upper and lower tanks are controlled by changing gas pressure in lower tank. As a result, it is confirmed that the entrained gas flow rate increases with increasing pressure difference between upper and lower tanks. By visualization of swirling annular flow in suction pipe, it is also observed that pressure drop in suction pipe increases with increase in entrained gas flow rate, which implies that entrained gas flow rate can be predicted by evaluation model based on pressure drop in swirling annular flow region.

Journal Articles

Signatures of the vortical quark-gluon plasma in hadron yields

Taya, Hidetoshi*; Park, A.*; Cho, S.*; Gubler, P.; Hattori, Koichi*; Hong, J.*; Huang, X.-G.*; Lee, S. H.*; Monnai, Akihiko*; Onishi, Akira*; et al.

Physical Review C, 102(2), p.021901_1 - 021901_6, 2020/08

 Times Cited Count:2 Percentile:57.67(Physics, Nuclear)

JAEA Reports

Flow separation at inlet causing transition and intermittency in circular pipe flow

Ogawa, Masuro*

JAEA-Technology 2019-010, 22 Pages, 2019/07

JAEA-Technology-2019-010.pdf:1.5MB

Transition phenomena from laminar to turbulent flow are roughly classified into three categories. Circular pipe flow of the third category is linearly stable against any small disturbance, despite that flow actually transitions and transitional flow exhibits intermittency. These are among major challenges that are yet to be resolved in fluid dynamics. Thus, author proposes hypothesis as follows; "Flow in a circular pipe transitions from laminar flow because of vortices released from separation bubble forming in vicinity of inlet of pipe, and transitional flow becomes intermittent because vortex-shedding is intermittent." Present hypothesis can easily explain why linear stability theory has not been able to predict transition in circular pipe flow, why circular pipe flow actually transitions, why transitional flow actually exhibits intermittency even due to small disturbance, and why numerical analysis has not been able to predict intermittency of transitional flow in circular pipe.

Journal Articles

Evaluation of gas entrainment flow rate using numerical simulation with interface-tracking method

Ito, Kei; Ohno, Shuji; Koizumi, Yasuo*; Kawamura, Takumi*

Proceedings of 10th International Topical Meeting on Nuclear Thermal Hydraulics, Operation and Safety (NUTHOS-10) (USB Flash Drive), 10 Pages, 2014/12

Journal Articles

Study on surface tension modeling for mechanistic evaluation of vortex cavitation

Ito, Kei; Ezure, Toshiki; Ohshima, Hiroyuki; Kawamura, Takumi*; Nakamine, Yoshiaki*

Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 6 Pages, 2014/11

The authors have been studied the vortex cavitation in sodium-cooled fast reactors. In this paper, the authors present a modified evaluation method for vortex cavitation, in which a surface tension is modeled mechanistically. Namely, the cavity radius is calculated in consideration of radial pressure distribution, saturated vapor pressure and the pressure jump condition at an interface. As the basic validation of the developed surface tension model, numerical analyses of a simple experiment under various velocity conditions are performed. The evaluation results give qualitatively appropriate tendency, that is, the cavity radius becomes larger with the higher liquid velocity and/or lower reference pressure which cause the larger pressure drop at the vortex. In addition, the authors evaluate the influence of the kinematic viscosity which plays an important role in the vortex cavitation occurrences in the experiments.

Journal Articles

Development of vortex model with realistic axial velocity distribution

Ito, Kei; Ezure, Toshiki; Ohshima, Hiroyuki

Nihon Kikai Gakkai Rombunshu (Internet), 80(818), p.FE0299_1 - FE0299_9, 2014/10

A vortex is considered as one of significant phenomena which may cause gas entrainment (GE) and/or vortex cavitation in sodium-cooled fast reactors. In this study, a new vortex model with realistic axial velocity distribution is proposed. As the verification, the new vortex model is applied to the evaluation of a simple vortex experiment, and shows good agreements with the experimental data in terms of the circumferential velocity distribution and the free surface shape. In addition, it is confirmed that the Burgers vortex model fails to calculate accurate velocity distribution with the assumption of uniform axial velocity. However, the calculation accuracy of the Burgers vortex model can be enhanced close to that of the new vortex model in consideration of the effective axial velocity which is calculated as the average value only in the vicinity of the vortex center.

Journal Articles

Effect of physical properties on gas entrainment rate from free surface by vortex, 2

Koizumi, Yasuo*; Ote, Naosuke*; Kamide, Hideki; Ohno, Shuji; Ito, Kei

Proceedings of 22nd International Conference on Nuclear Engineering (ICONE-22) (DVD-ROM), 7 Pages, 2014/07

Journal Articles

Vortex imaging of Tl-based superconductors with a scanning SQUID microscopy

Okayasu, Satoru; Nishio, Taichiro; Ono, Masao; Mashimo, Tsutomu; Tanaka, Yasutomo*; Iyo, Akira*

Physica C, 445-448, p.245 - 248, 2006/10

 Times Cited Count:1 Percentile:7.01(Physics, Applied)

Vortex imagings of Tl-2223 thin film are achieved below Tc with a scanning SQUID microscope. Vortex arrangements are almost the same just below Tc, indicating the existence of strong pinning centers in the sample. The origin of the strong pinning centers comes from the morphological inhomogeneity on the surface.

Journal Articles

Penetration of vortices into micro-superconductors observed with a scanning SQUID microscope

Nishio, Taichiro; Okayasu, Satoru; Suzuki, Junichi; Kadowaki, Kazuo

Physica C, 412-414(Part1), p.379 - 384, 2004/10

We have studied the vortex states in a meoscopic superconductor with geometrical constraints such as disks, triangles, squares, etc. with dimensions between 30-50$$mu$$m using a scanning SQUID microscope (SQM2000,Seiko Instruments Inc.). The sample was fabricated by electron lithography and Focused Ion Beam (FIB) techniques. Quantized vortices enter into a mesoscopic superconductor discretely as a function of magnetic field accompanied by the sequential step-wise jump of magnetization of the superconductor. Quantitative as well as qualitative analyses of spatial vortex arrangement as a function of the number of vortices will be shown in comparison with the recent theoretical predictions.

Journal Articles

Friedel oscillation in charge profile and position dependent screening around a superconducting vortex core

Machida, Masahiko; Koyama, Tomio*

Physical Review Letters, 90(7), p.077003_1 - 077003_4, 2003/02

 Times Cited Count:35 Percentile:81(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Vortex imaging of magnetic superconductor HoNi$$_{2}$$B$$_{2}$$C by scanning SQUID microscopy

Hata, Yoshiaki; Suzuki, Junichi; Kakeya, Itsuhiro*; Kadowaki, Kazuo*; Nakayama, Satoshi*; Nagata, Atsushi*; Odawara, Akikazu*; Chinone, Kazuo*

Physica C, 378-381(Part1), p.420 - 423, 2002/10

no abstracts in English

Journal Articles

Effects of flow velocity fluctuation around excited cylinder on cylinder oscillation

Kondo, Masaya; Anoda, Yoshinari

Nihon Kikai Gakkai Rombunshu, B, 68(665), p.86 - 93, 2002/01

no abstracts in English

Journal Articles

Water flow simulation test on flow-induced oscillation of thermowell in prototype fast breeder reactor "MONJU"

Kondo, Masaya; Anoda, Yoshinari

JSME International Journal, Series B, 44(4), p.688 - 694, 2001/11

no abstracts in English

Journal Articles

Vortex dissipation and level dynamics for the layered superconductors with impurities

Fujita, Ayumi

Physical Review B, 64(6), p.064504_1 - 064504_6, 2001/08

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

We study parametric level statistics of the discretized excitation spectra inside a moving vortex core in layered superconductors with impurities. The universal conductivity is evaluated numerically for the various values of rescaled vortex velocities $$kappa$$ from the clean case to the dirty limit case. The random matrix theoretical prediction is verified numerically in the large $$kappa$$ regime. On the contrary in the low velocity regime, we observe $$sigma_{xx} propto kappa^{2/3}$$which is consistent with the theoretical result for the super-clean case, where the energy dissipation is due to the Landau-Zener transition which takes place at the points called ``avoided crossing''.

Journal Articles

Study on oscillated flow around excited cylinder using built-in electromagnetic flowmeters

Kondo, Masaya; Anoda, Yoshinari

Emerging Technologies for Fluids, Structures and Fluid-Structure Interaction, 2001 (PVP-Vol.431), p.111 - 117, 2001/07

no abstracts in English

Journal Articles

Effects of defect morphology on the properties of vortex system in Bi$$_{2}$$Sr$$_{2}$$CaCu$$_{2}$$O$$_{8+delta}$$ irradiated with GeV heavy ions

Kuroda, N.; Ishikawa, Norito; Chimi, Yasuhiro; Iwase, Akihiro; Ikeda, Hiroshi*; Yoshizaki, Ryozo*; Kambara, Tadashi*

Physical Review B, 63(22), p.224502_1 - 224502_5, 2001/06

 Times Cited Count:8 Percentile:45.98(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Study of alternate vortices effect on in-line oscillations of flexible cylinder

Kondo, Masaya; Anoda, Yoshinari

Emerging Technologies in Fluids, Structures, and Fluid/Structure Interactions (PVP-Vol.414-1), p.171 - 177, 2000/07

no abstracts in English

Journal Articles

Evaluation method of performance of siphon break value as core covering system for water-cooled test and research reactors

; Kumada, Hiroaki; Kaminaga, Fumito*

Nihon Genshiryoku Gakkai-Shi, 42(4), p.325 - 333, 2000/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Effect of alternate-vortex on flow-induced in-line oscillation

; Anoda, Yoshinari

Nihon Kikai Gakkai Rombunshu, C, 65(639), p.4252 - 4259, 1999/11

no abstracts in English

Journal Articles

The Order of phase transition of reentrant line in detwinned YBCO single crystal

Okayasu, Satoru; Asaoka, Hidehito

Physica B; Condensed Matter, 317-318, p.633 - 636, 1999/00

no abstracts in English

37 (Records 1-20 displayed on this page)