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JAEA Reports

Basic study on flow separation phenomenon in cooling system piping in fast reactors; Clarification of complex flow structure in a multi-elbow in a high Reynolds number regime (Joint research report in JFY2008 and JFY2009)

Ebara, Shinji*; Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Aizawa, Kosuke; Yamano, Hidemasa

JAEA-Research 2013-011, 72 Pages, 2013/10

JAEA-Research-2013-011.pdf:11.34MB

In Tohoku University, different scale model experiments were carried out in order to clarify unsteady flow fields and pressure fluctuation characteristics in the cold leg piping by means of visualization experiment and pressure measurement, respectively, and to investigate the scale effect. In JFY2008, the visualization experiment by PIV measurement for the 1/15 scale piping was carried out using a double elbow geometry. Besides, shakedown tests of the 1/7 scale model were conducted for the case of a single elbow. In JFY2009, visualization experiments for the 1/7 scale models with the single and a three-dimensionally connected double elbow geometries were carried out. From these obtained data, effects of the multiple elbows on the flow field were assessed. In addition, the pressure measurements for single elbow flows by using 1/15 and 1/7 scale models were performed. In JAEA, numerical analyses for the 1/7 scale double elbow experiments were performed using the commercial thermal-hydraulics code STAR-CD. The analyses showed that the calculated velocity distributions were in good agreement with the visualization experimental results. It was confirmed, from these analyses, that the URANS analysis method validated for the single elbow flow has applicability to the double elbow flow.

Journal Articles

Unsteady elbow pipe flow to develop a flow-induced vibration evaluation methodology for JSFR

Yamano, Hidemasa; Tanaka, Masaaki; Ono, Ayako; Murakami, Takahiro*; Iwamoto, Yukiharu*; Yuki, Kazuhisa*; Sago, Hiromi*; Hayakawa, Satoshi*

Proceedings of International Conference on Fast Reactors and Related Fuel Cycles (FR 2009) (CD-ROM), 12 Pages, 2012/00

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in JSFR, in particular emphasizing on recent R&D activities that investigate unsteady elbow pipe flow. The experiment using the 1/3-scale test section was performed to investigate the effect of swirl flow at the inlet. Although the flow separation region was distorted at the downstream from the elbow, the experiment clarified that the effect of swirl flow on pressure fluctuation onto the pipe wall was not significant. The simulation revealed that Reynolds number scarcely affects flow patterns and flow velocity distributions.

Journal Articles

Matched refractive-index PIV visualization of complex flow structure in a three-dimentionally connected dual elbow

Yuki, Kazuhisa*; Hasegawa, Shunsuke*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Aizawa, Kosuke; Yamano, Hidemasa

Nuclear Engineering and Design, 241(11), p.4544 - 4550, 2011/11

 Times Cited Count:23 Percentile:88.07(Nuclear Science & Technology)

Journal Articles

Unsteady elbow pipe flow to develop a flow-induced vibration evaluation methodology for Japan sodium-cooled fast reactor

Yamano, Hidemasa; Tanaka, Masaaki; Murakami, Takahiro*; Iwamoto, Yukiharu*; Yuki, Kazuhisa*; Sago, Hiromi*; Hayakawa, Satoshi*

Journal of Nuclear Science and Technology, 48(4), p.677 - 687, 2011/04

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in Japan Sodium-cooled Fast Reactor (JSFR), in particular emphasizing on recent R&D activities that investigate unsteady elbow pipe flow.

Journal Articles

Pressure fluctuation characteristics of complex turbulent flow in a single elbow with small curvature radius for a sodium-cooled fast reactor

Ebara, Shinji*; Aoya, Yuta*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Yuki, Kazuhisa*; Aizawa, Kosuke; Yamano, Hidemasa

Journal of Fluids Engineering, 132(11), p.111102_1 - 111102_7, 2010/11

 Times Cited Count:8 Percentile:45.74(Engineering, Mechanical)

A multi-elbow piping system is adopted for the Japan Sodium-cooled Fast Reactor (JSFR) cold-legs. Flow Induced Vibration (FIV) is considered to appear due to complex turbulent flow with very high Reynolds number in the piping. In this study, pressure measurement for a single elbow flow is conducted to elucidate pressure fluctuation characteristics originated from turbulent motion in the elbow, which lead potentially to the FIV. Two different scale models, 1/7 and 1/14-scale simulating the JSFR cold-leg piping, are tested experimentally to confirm whether a scale effect in pressure fluctuation characteristics exists. A distinguishing peak can be seen in each power spectrum density (PSD) profile of pressure fluctuation obtained in and downstream of the flow separation region for both scaled models. When nondimensionalized, the PSD profiles show good correspondence regardless of scale model and even of Reynolds number simulated in this study.

Journal Articles

Pressure measurement test of single elbow simulating Na cooled fast reactor cold-leg piping

Ebara, Shinji*; Aoya, Yuta*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Yuki, Kazuhisa*; Aizawa, Kosuke; Yamano, Hidemasa

Proceedings of 18th International Conference on Nuclear Engineering (ICONE-18) (CD-ROM), 9 Pages, 2010/05

In this study, pressure measurement test is conducted to find out the FIV characteristic features related to the elbow turbulent flow, using 1/7 scale experimental loop simulating the JSFR cold leg piping. As the first step of multielbow piping, pressure measurement for single elbow was performed. The same measurement procedure was taken as a 1/15 scale experiment to assess the influence originated from the different scale flow at the same Reynolds number.

Journal Articles

Unsteady hydraulic characteristics in large-diameter pipings with elbow for JSFR, 3; Flow structure in a 3-dimentionally connected dual elbow simulating cold-leg piping in JSFR

Yuki, Kazuhisa*; Hasegawa, Shunsuke*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Aizawa, Kosuke; Yamano, Hidemasa

Proceedings of 13th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-13) (CD-ROM), 11 Pages, 2009/09

In this study, the flow structures in a 3-dimentionally connected dual elbow, which simulates a part of the cold leg, are visualized by PIV measurement, and it is discussed on the detailed flow transition from the 1st elbow to the 2nd elbow and the generation of unsteady flow such as a separation that influences flow-induced vibration. Experimental apparatus has a 1/15 scale test section of actual design whose inner diameter and curvature radius ratio are 56mm and 1.0, respectively. For visualization without any image distortion, matched refractive-index PIV measurement is carried out using NaI solution as the working fluid. The Reynolds number is 50,000, and the inlet flow condition to the test section is a fully developed turbulent flow. It is confirmed that it generates a separation along the inner wall of the 1st elbow and one large swirling flow in the 2nd elbow. Furthermore, unsteady flow formed in and/or behind the separation region is transported downstream and flows into the center area of the 2nd elbow.

JAEA Reports

Basic study on flow separation phenomenon in cooling system piping in fast reactors; Clarification of complex flow structure in a multi-elbow in a high Reynolds number regime (Joint research report in FY2007)

Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Nakanishi, Shigeyuki*; Aizawa, Kosuke; Yamano, Hidemasa

JAEA-Research 2009-017, 55 Pages, 2009/08

JAEA-Research-2009-017.pdf:16.5MB

At Tohoku University, 1/15 scale and 1/7 scale flow tests are being performed in order to clarify an unsteady flow structure in the cold leg piping and to investigate the scale effect. In FY2007, the 1/15 scale test was carried out using a double elbow geometry. It was confirmed that there existed a separation along the inner wall of the 1st elbow and a large swirling flow in the 2nd elbow. Furthermore, the unsteady flow formed in and/or behind the separation region was transported downstream and flows into the center area of the 2nd elbow. At JAEA, a numerical analytical evaluation method is being developed to evaluate the feasibility of the reactor design. In FY2007, numerical analyses for the 1/15 scale test were performed using the commercial thermal-hydraulics code FLUENT. The analyses showed that the trend of calculated velocity distributions was in good agreement with the visualization test results.

Journal Articles

Suppression of high-cycle thermal fatigue at a mixing tee with a 90-degree bend upstream by changing its geometry

Yuki, Kazuhisa*; Ohara, Hiroshi*; Hashizume, Hidetoshi*; Tanaka, Masaaki; Muramatsu, Toshiharu; Toda, Saburo*

Proceedings of 7th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, Operation and Safety (NUTHOS-7) (CD-ROM), 21 Pages, 2008/10

Velocity measurement by PIV (Particle Image Velocimetry) and measurement of fluid-temperature are conducted in a mixing tee with an elbow on the upstream side of the tee. Parameters in the experiment are the distance between the elbow pipe exit and the tee and the curvature radius of the elbow pipe. By the experiment, certain suppression techniques for high cycle thermal fatigue in the mixing tee area are proposed to control the distance between the elbow and the tee according to the curvature radius of the elbow.

Journal Articles

Influence of secondary flow generated in a 90-deg bend on the thermal-hydraulic characteristics in a mixing tee

Yuki, Kazuhisa*; Sugawara, Yoshimasa*; Hosseini, S. M.*; Hashizume, Hidetoshi*; Toda, Saburo*; Tanaka, Masaaki; Muramatsu, Toshiharu

Nuclear Science and Engineering, 158(2), p.194 - 202, 2008/02

 Times Cited Count:2 Percentile:18.72(Nuclear Science & Technology)

This study aims at clarifying a relationship between non-isothermal fluid mixing in a T-junction area with 90-deg bend upstream and temperature fluctuations induced by the unstable mixing, by visualizing the flow fields with particle image velocimetry and measuring fluid-temperature fluctuation in the vicinity of a wall. By the experiment, flow-pattern of the jet flowing out from a branch pipe and characteristics of temperature fluctuation in mixing area were clarified in relation to the secondary flow generated in the 90-deg bend.

Journal Articles

Control technique of high-cycle thermal fatigue at a mixing tee with a 90-degree bend upstream by changing its location

Ohara, Hiroshi*; Yuki, Kazuhisa*; Hoseini, S. M.*; Hashizume, Hidetoshi*; Tanaka, Masaaki

Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 10 Pages, 2007/04

When temperature fluctuation in mixing tee pipe is transported to the structure, it may lead high-cycle thermal fatigue in the structure. Therefore, it is important to control the high-cycle thermal fatigue. In a 90-degree bend located in upstream of the tee, an unsteady secondary flow arises. The secondary flow affects the fluid mixing in tee and the distance between the tee and the bend is one of the most important parameters to characterize the temperature fluctuation. The temperature fluctuation and the fluid mixing structure are investigated experimentally varied the distance between the tee and the bend. When the tee is located at the close to the bend, the fluid mixing area tends to shift to the inside of the bended pipe. And the temperature fluctuation intensity becomes lower and decays faster in the stream direction. Experimental results suggest that changing the distance between the tee and the bend is useful to control the high-cycle thermal fatigue.

Journal Articles

Focusing quality of a split short laser pulse

Kotaki, Hideyuki; Oishi, Yuji*; Nayuki, Takuya*; Fujii, Takashi*; Nemoto, Koshichi*; Nakajima, Kazuhisa

Review of Scientific Instruments, 78(3), p.036102_1 - 036102_3, 2007/03

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

Investigation of thermal hydraulic mixing mechanism in T-junction pipe with a 90-degree bend in upstream side for mitigation and controlling of thermal-striping phenomena (Joint research)

Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Tanaka, Masaaki; Muramatsu, Toshiharu

JAEA-Research 2006-025, 47 Pages, 2006/03

JAEA-Research-2006-025.pdf:4.26MB

In T-junction pipe, temperature fluctuation is induced due to unstable fluid mixing. Development of the relaxation and control techniques for the thermal fatigue is one of the most important issues in the future plant design. If a 90-degree bend exists in the upstream of the mixing tee in the piping system of power plants, a secondary flow formed in the bend makes the fluid mixing phenomena even more complex. This study aims at clarifying effects of curvature ratio of the bend on the non-isothermal fluid mixing in the Tee-junction area and the temperature fluctuation induced by the unstable mixing, by visualizing the flow fields with PIV and measuring fluid-temperature fluctuation in the vicinity of wall. From the visualization, it is clarified that a high-temperature jet flowing out from a branch pipe swings and sways near the wall, which leads to higher temperature fluctuation than that in a case without the 90-degree bend. In addition, in the case that there exists a separation in the bend, the fluid mixing and the temperature fluctuation characteristics including its damping in the downstream direction are completely different from those without the separation. Furthermore, in the case using the bend that doesn't produce the separation, there are cautionary conditions in which the temperature fluctuation is maximized in a transition regime of a stratified flow and a turn-jet flow. It seems that the principal cause for this is repetition generation and disappearance of a circulating flow formed behind the jet due to an interaction between unsteady behavior of a secondary flow in a decay process after the bend and the wakes formed behind the jet, which leads to the vigorous oscillation of jet near the wall. For the prediction of the temperature fluctuation, it's possible to predict it in each fluid mixing pattern.

Journal Articles

Quasi-monoenergetic electron beam generation during laser pulse interaction with very low density plasmas

Yamazaki, Atsushi; Kotaki, Hideyuki; Daito, Izuru; Kando, Masaki; Bulanov, S. V.; Esirkepov, T. Z.; Kondo, Shuji; Kanazawa, Shuhei; Homma, Takayuki*; Nakajima, Kazuhisa; et al.

Physics of Plasmas, 12(9), p.093101_1 - 093101_5, 2005/09

 Times Cited Count:69 Percentile:90.26(Physics, Fluids & Plasmas)

no abstracts in English

JAEA Reports

Elucidation of Thermal Hydraulic Mixing Mechanism in a Mixing Tee Area with a 90-degree Bend Upstream and Development of Thermal-striping Relaxation and Control Methods

Sugawara, Yoshimasa*; Yuki, Kazuhisa*; Hashizume, Hidetoshi*; Tanaka, Masaaki; Muramatsu, Toshiharu

JNC TY9400 2004-027, 65 Pages, 2004/10

JNC-TY9400-2004-027.pdf:12.54MB

In this study, non-isothermal fluid mixing experiments in a T-junction area with a 90-degree bend upstream were carried out to estimate the fluid-temperature fluctuation in the vicinity of wall. The temperature fluctuations for various flow mixing conditions were measured, changing a velocity ratio and a pipe diameter ratio of a main pipe to a branch pipe to quantitatively evaluate the effect of a secondary flow on the temperature fluctuation. In addition, by analyzing both the visualization data taken by a PIV system and the temperature fluctuation data, it was attempted to construct a prediction formula for the temperature fluctuation.

Oral presentation

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor,6; PIV visualization on complex flow field in a cold-leg multi-elbow to a scale of 1/15

Yoshida, Kazuhiro*; Yuki, Kazuhisa*; Sato, Tsukasa*; Hashizume, Hidetoshi*; Yamano, Hidemasa; Kotake, Shoji

no journal, , 

Flow dynamics in an elbow pipe has been observed by a PIV flow visualization experiments with a 1/15 scale test facility simulating a cold-leg piping in a sodium-cooled fast reactor. This paper also reports the overview of the facility of an upcoming 1/7 scale test and its plan.

Oral presentation

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor, 15; PIV visualization of single elbow flow with a 1/7 scale experimental loop simulating JSFR cold-leg piping

Yuki, Kazuhisa*; Sato, Tsukasa*; Yoshida, Kazuhiro*; Hashizume, Hidetoshi*; Aizawa, Kosuke; Yamano, Hidemasa

no journal, , 

To investigate the flow pattern in the cold-leg (multi-elbow geometry) of a sodium-cooled fast reactor, a 1/7-scale water experimental facility was made in this study. First of all, the flow pattern in a single elbow was measured by a PIV technique.

Oral presentation

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor, 18; PIV visualization of single elbow flow with Re=10$$^{6}$$

Sato, Tsukasa*; Ebara, Shinji*; Hashizume, Hidetoshi*; Yusa, Noritaka*; Yuki, Kazuhisa*; Aizawa, Kosuke; Yamano, Hidemasa

no journal, , 

To clarify a flow pattern in a multiple elbow pipe of cold-leg in sodium-cooled fast reactor, the 1/7 scale flow experiment was performed as the first step to measure the flow velocity distribution in a single elbow pipe under Re=1$$times$$10$$^{6}$$ by using the PIV technique.

Oral presentation

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor, 21; Pressure fluctuation measurement test of single elbow of 1/7 and 1/15 scaled pipes

Aoya, Yuta*; Sato, Tsukasa*; Ebara, Shinji*; Hashizume, Hidetoshi*; Yuki, Kazuhisa*; Aizawa, Kosuke; Yamano, Hidemasa

no journal, , 

In order to clarify the hydraulic and vibration behaviors in the primary cooling piping, a flow-induced vibration test with water has been begun using a 1/7-scale and a 1/15-scale L-shaped elbow test section, which simulated the JSFR hot-leg piping. The peak of St number 0.5 was confirmed in both experiments.

Oral presentation

Study on flow-induced-vibration evaluation of large-diameter pipings in a sodium-cooled fast reactor, 24; PIV measurement for dual elbow flow using 1/7-scale model of cold-leg piping

Ebara, Shinji*; Hashizume, Hidetoshi*; Yuki, Kazuhisa*; Aizawa, Kosuke; Yamano, Hidemasa

no journal, , 

Experiment on flow in a dual elbow has been conducted to clarify the complex flow behavior, using a 1/7-scale model of cold-leg piping of a sodium-cooled fast reactor. Several cases of elbow effects have been examined by using PIV measurement to evaluate flow fields which have strong unsteadiness and resultant effect on flow-induced vibration, e.g. separation vortex in a range of high Reynolds numbers, and also by comparing the result with that of a single elbow.

21 (Records 1-20 displayed on this page)