Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

Numerical simulations of contaminated spherical drops falling through a stagnant liquid at low Reynolds numbers are carried out using the finite difference method. The numerical results are used to describe the behavior of the surfactant concentrations and to understand the surfactant effects on the fluid motions in detail. The predicted interfacial surfactant concentration, Γ, is almost zero for angles, θ, below a certain value (the stagnant-cap angle, θcap), whereas it steeply increases and reaches a large value for θ>θcap (the stagnant-cap region). The increase in the initial surfactant concentration, C0, in the drop enhances the adsorption from the drop to the interface, which results in the increase in Γ and the decrease in θcap. Peaks appear in the predicted Marangoni stresses around θcap, which causes similar peaks in the pressure distribution. The high-pressure spots prevent the fluid motion along the interface, which results in the formation of the stagnant-cap region and the attenuation of the tangential velocity in the continuous phase. The surfactant flux from the bulk to the interface decreases C in the vicinity of the interface for θ<θcap and the weak diffusion cannot compensate for the reduction in C by adsorption, which results in C at the interface smaller than C0. The pattern of the low C region is determined by the advection and does not smear out because of a small diffusive flux.

DOI： 10.3390/fluids7020055

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/j.nucengdes.2020.110948

Scopus

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Begell House  

DOI： 10.1615/multscientechn.2021040158

researchmap

Publishing type：Research paper (international conference proceedings)   Publisher：American Society of Mechanical Engineers  

Abstract

This paper presents an analysis of the performance of the Spatial Filter Velocimetry (SFV) technique applied to external flows across tube bundles to evaluate the benefits of using low particle concentration in a complex geometry. The experimental vector velocity fields were obtained in a tube bundle test section made of acrylic with 20 rows of 4 tubes of 20mm O.D. mounted in a normal triangular configuration and transversal pitch per diameter ratio of 1.25. The SFV results reliability was evaluated by comparing the volumetric flow rates estimated by the experimental vector velocity fields with the volumetric flow rates measured by the flowmeter, showing good agreement. Additionally, the experimental results are used to check the validity of numerical results obtained through CFD simulation. The experiments were conducted for Reynolds numbers of 909, 1842 and 3902. The velocity profiles obtained through the SFV technique agree with the CFD simulations results, which indicate consistent results for both analyzes. Therefore, the numerical and experimental results indicate that the SFV technique provides accurate velocity data and is suitable to be applied to complex geometries, especially in regions away of the test section wall due to the good visibility provided by low particle concentration.

DOI： 10.1115/fedsm2020-20251

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10494-020-00143-z

researchmap

Other Link： http://link.springer.com/article/10.1007/s10494-020-00143-z/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s40430-020-02293-7

researchmap

Other Link： http://link.springer.com/article/10.1007/s40430-020-02293-7/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ijmultiphaseflow.2020.103207

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Society for Multiphase Flow  

DOI： 10.3811/jjmf.2019.012

researchmap

Publishing type：Research paper (international conference proceedings)  

researchmap

Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2019.110223

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.2019031210

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.2019029476

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Inc.  

DOI： 10.1016/j.expthermflusci.2018.03.015

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/j.nucengdes.2018.01.043

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/j.ijmultiphaseflow.2017.08.007

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2017.07.087

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijmultiphaseflow.2017.07.003

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2017.07.002

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

<p>One-region computations with the annular flow model were done for counter-current flow limitation (CCFL) at the sharp-edged lower end of vertical pipes to evaluate effects of diameters and fluid properties on CCFL characteristics. CCFL characteristics computed with several correlations for interfacial friction factors were compared with CCFL data and the correlation proposed by Bharathan et al. (which is a function of void fraction) was selected. The adjustment factors were obtained to give good agreement between CCFL characteristics computed with the correlation by Bharathan et al. and CCFL data and were correlated with the viscosity ratio of gas and liquid phases and the dimensionless diameter. By using the correlation for interfacial friction factors by Bharathan et al. modified with the viscosity ratio of gas and liquid phases and the dimensionless diameter, effects of diameters and fluid properties on CCFL characteristics were computed.</p>

DOI： 10.3811/jjmf.31.37

CiNii Books

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2017.01.058

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本混相流学会  

<p>One-region computations with the annular flow model were done for counter-current flow limitation (CCFL) at the sharp-edged lower end of vertical pipes to evaluate effects of diameters and fluid properties on CCFL characteristics. CCFL characteristics computed with several correlations for interfacial friction factors were compared with CCFL data and the correlation proposed by Bharathan et al. (which is a function of void fraction) was selected. The adjustment factors were obtained to give good agreement between CCFL characteristics computed with the correlation by Bharathan et al. and CCFL data and were correlated with the viscosity ratio of gas and liquid phases and the dimensionless diameter. By using the correlation for interfacial friction factors by Bharathan et al. modified with the viscosity ratio of gas and liquid phases and the dimensionless diameter, effects of diameters and fluid properties on CCFL characteristics were computed.</p>

DOI： 10.3811/jjmf.31.37

CiNii Books

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/j.ijmultiphaseflow.2017.07.003

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Congress on Advances in Nuclear Power Plants, ICAPP  

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

<p>Characteristics of counter-current flow limitation (CCFL) inside vertical pipes with sharp-edged upper end (CCFL-P/SE) and with round-edged upper and lower ends (CCFL-P) were evaluated to clarify the dependence of the limiting locations. The CCFL is defined by the relationship between the gas and liquid volumetric fluxes (<i>J_G</i> and <i>J_L</i>) under a quasi-steady state after onset of flooding. CCFL correlations were constructed for CCFL-P/SE and CCFL-P based on the previous experimental data. The correlations were compared to the characteristics of CCFL at the vertical pipes of the sharp-edged upper end (CCFL-U) and the sharp-edged lower end (CCFL-L). CCFL-P has the highest liquid volumetric flux when CCFL occurs, and the lowest is CCFL-L. For the Wallis correlation, selection of the characteristic length of <i>w</i> = <i>D</i>^{(1-<i>β</i>)}<i>L</i>^<i>β</i> (where <i>D</i> and <i>L</i> respectively denote the diameter and the Laplace capillary length) is quite important. Our results have indicated that CCFL-P/SE and CCFL-P are also expressed by <i>β</i> ≈ 0.5, CCFL-U is expressed by <i>β</i> = 1, and CCFL-L is expressed by <i>β</i> = 0.</p>

DOI： 10.3811/jjmf.30.392

CiNii Books

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2016.08.030

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：化学工学会  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/transjsme.15-00685

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.applthermaleng.2016.05.010

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/00223131.2015.1057253

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

A gas-liquid separation cycle is one of the technologies that can improve the cooling capacity. In this study, the availability of a conventional gas-liquid separator for the room air conditioner of 7.1 kW class was evaluated and an improved gas-liquid separator that has an inflow pipe with a bottom hole and some side holes was proposed. The proposed gas-liquid separator was further improved for easy manufacturing and the gas separation efficiency and the cooling capacity when the gas-liquid separation cycle was applied to the room air conditioner of 7.1 kW class were investigated. As a result, approximately complete gas-liquid separation was realized and the cooling capacity was improved by about 3%.

DOI： 10.3811/jjmf.30.49

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JLC/20022423281?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijmultiphaseflow.2015.10.003

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/ceat.201500063

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/00223131.2014.990533

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1252/jcej.14we241

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本機械学会  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.expthermflusci.2014.09.010

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Begell House Inc.  

DOI： 10.1615/MultScienTechn.v27.i1.40

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Begell House Inc.  

DOI： 10.1615/MultScienTechn.v27.i1.40

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijmultiphaseflow.2014.05.008

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：化学工学会  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2013.07.006

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2013.10.031

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/00223131.2013.862189

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/1.4872124

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/1.4872108

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1252/kakoronbunshu.40.275

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2013.06.009

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00348-013-1597-0

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：American Nuclear Society  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00348-013-1538-y

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatfluidflow.2013.01.004

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2013.06.009

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.nucengdes.2011.11.035

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Slugging of a stagnant liquid at a V-shaped elbow in a hilly-terrain pipeline is experimentally investigated to obtain information on flow regime and critical conditions of the slugging. According to flow observation using a high-speed camera, the flow is classified into seven flow regimes, i.e. static puddle, wavy puddle, periodic slug flow, periodic semi-slug flow, aperiodic semi-slug flow, film flow and pebble flow. The onset of the slugging is well predicted not by the Mishima-Ishii's model, but by the Wallis parameter used for flooding in a pipe. This means that the slugging at the V-shaped elbow is similar to the flooding caused by interfacial shear stress. An empirical correlation based on a modified Wallis parameter is proposed to represent the effects of inclination angle, pipe diameter and fluid properties on the onset of slugging.

DOI： 10.1299/kikaib.78.1292

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00348-011-1259-z

Web of Science

researchmap

Publishing type：Research paper (international conference proceedings)  

researchmap

Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00348-011-1109-z

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.v24.i3.20

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/1.3694707

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1063/1.3694718

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2012/754724

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2012/174838

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Begell house  

DOI： 10.1615/MultScienTechn.v24.i3.20

Scopus

researchmap

Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1115/AJK2011-10035

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/kikaib.77.2263

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/kikaib.77.2263

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

Effects of liquid volumetric flux <i>J_L</i> and flow pattern in a decompression nozzle on the mean diameter and number density of micro-bubbles generated by using a pressurized dissolution method are experimentally investigated. The bubble diameter and number density are measured by using a phase Doppler anemometry at the exit of the decompression nozzle. The flow pattern in the decompression nozzle was observed by using a high speed camera. The experimental results indicate that the diameter and number density strongly depends on the flow pattern in the decompression nozzle, and their characteristics are classified into three regimes: (1) few bubbles are generated when no cavitation occurs, (2) when bubble cavitation takes place, the mean bubble diameter keeps low values which do not depend on <i>J_L</i> so much and the bubble number density increases with <i>J_L</i>, and (3) the mean bubble diameter increases with <i>J_L</i> whereas the number density does not depend on <i>J_L</i> when flow pattern in the nozzle is sheet cavitation.

DOI： 10.3811/jjmf.24.462

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00362111260?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3811/jjmf.23.547

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.76.765_763

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1615/MultScienTechn.v22.i3.30

Scopus

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

High spatial and temporal resolutions are required in velocity measurements for turbulent flows to examine turbulence characteristics accurately. In this study, we proposed a spatial filter velocimetry (SFV) based on a frequency analysis of time-series spatially-filtered particle images. Since this method can measure velocity from one particle in a measurement region, it enables us to measure the velocity with high spatial and temporal resolutions. We developed a SFV system and applied it to laminar and turbulent flows in a duct to examine its feasibility. Through comparisons between the velocities measured by SFV and LDV, we confirmed that SFV accurately measures the mean velocity and turbulent intensity with spatial and temporal resolutions as high as LDV.

DOI： 10.1299/jsmemecjo.2010.7.0_57

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Since the conservation equation of turbulence kinetic energy (TKE) involves correlations among local instantaneous gradients of fluctuating velocities, it is indispensable to measure the velocity gradients as well as the velocity components. The authors developed a molecular tagging method using photobleaching (PB-MTV), which can measure not only velocity but also its gradient by making use of the translation and deformation of a tag. We applied the PB-MTV to turbulent bubbly flows in a square duct. The experimental results indicate that the presence of bubbles increases not only the production rate but also the dissipation rate of TKE. Although the low Reynolds number k-z model well evaluates the production rate of TKE in the bubbly flow, modification of the diffusion term is required for the bubbly flows.

DOI： 10.1299/jsmemecjsm.2010.9.0_153

CiNii Books

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00348-009-0690-x

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Numerical simulations based on a three-dimensional two-way bubble tracking method are carried out to predict bubble motions in a square duct with an obstacle and in a two-by-three rod bundle with a grid spacer. Comparisons between measured and predicted bubble motions demonstrate that the two-way bubble tracking method gives good predictions for trajectories of small bubbles in the upstream side of the grid spacer in the rod bundle geometry. The predicted bubble trajectories clearly show that bubbles are apt to migrate toward the rod surface in the vicinity of the bottom of the grid spacer. Analysis of forces acting on the bubbles confirms that pressure gradient force induced by the presence of the spacer is the main cause of the bubble lateral migration toward the rod surface. Motions of steam bubbles at a nominal operating condition of a pressurized water reactor (PWR) are also predicted by using the bubble tracking method, which indicates that steam bubbles also migrate toward the rod surface at the upstream side of the spacer due to the spacer-induced pressure gradient force.

DOI： 10.1299/jpes.3.393

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1115/1.3078701

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

Partial length rods (PLR) are used in fuel bundles of BWR to reduce pressure drops in two-phase regions and to optimize the power distribution. Since little is known about effects of PLR on two-phase flows, air-water two-phase flow around PLRs in a four by four rod bundle is visualized by using a high-speed video camera. The experimental apparatus consists of acrylic channel box and transparent rods. Air and water at atmospheric pressure and room temperature are used for the gas and liquid phases, respectively. The ranges of the gas and liquid volume fluxes, <I>J<SUB>G</SUB></I> and <I>J<SUB>L</SUB></I>, are 0.4 < <I>J<SUB>L</SUB></I> < 2.0 m/s and 0.06 < <I>J<SUB>G</SUB></I> < 8.85 m/s, which cover typical two-phase flow patterns appearing in the fuel bundle. As a result, the following conclusions are obtained. (1) In churn flows at high <I>J<SUB>L</SUB></I>, the flow pattern in the downstream of PLR transits to slug flow, and the flow patterns in the surrounding subchannels transit to bubbly flow due to the redistribution of gas flow. (2) In annular flow, the liquid film on the PLR forms a liquid column above the end cap of PLR. Drops are generated by column breakup and deposit on liquid films on the neighboring rods. (3) The liquid film thickness on the surface of neighbor rods facing the PLR increases and it reduces that on their opposite surface in the downstream of PLR.

DOI： 10.3811/pmfr.4.61

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00329084262?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ces.2009.09.017

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.75.749_68

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Physics Publishing  

DOI： 10.1088/1742-6596/147/1/012016

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3811/jjmf.22.403

CiNii Books

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Cavitation in a cylindrical nozzle and liquid jets discharged from the nozzle are simultaneously visualized using a high-speed camera to investigate the mechanism of liquid jet atomization induced by the fully-developed cavitation. Three mirrors are used to capture the front view of liquid jet interfaces and the side view of cavitation clouds within a frame of the camera. The high-speed visualization confirms that the collapse of a cavitation cloud near the nozzle exit induces a ligament formation not only for 2D nozzles but also for cylindrical nozzles. The visualization also finds that the collapse of a large cavitation cloud tends to cause the formation of a large ligament, while that of a small cloud results in a small ligament.

DOI： 10.1299/jfst.3.633

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The effects of nozzle geometry on cavitation in the nozzle of pressure atomizers and the liquid jet are examined using various two-dimensional (2D) nozzles with different geometries. Then, whether or not the conventional cavitation numbers can be used to predict the formation of supercavitation, in which liquid jet atomization is enhanced, is examined. As a result, we confirm that (1) the thickness of the cavitation zone increases with the ratio <i>C_u</i> of the cross-sectional area upstream of the nozzle to that of the nozzle, (2) the spray angle increases with <i>C_u</i>, (3) the formation of supercavitation can be predicted using the cavitation number σ_c' in which the effects of the flow contraction and the frictional pressure drop are taken into account, and (4) the conventional cavitation numbers σ, σ₂ and σ₃ cannot predict the formation of supercavitation in nozzles with different geometries.

DOI： 10.1299/jfst.3.622

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Effects of inlet bubble diameter on void and bubble size distributions in poly-dispersed bubbly flow in a rectangular bubble column under high gas volumetric flux conditions are experimentally investigated. Three types of gas distributors are used to form bubbly flows with different inlet bubble diameters at a constant gas flow rate. The conclusions obtained are as follows : (1) the bubble size distribution reaches an equilibrium state at which the birth rate of bubbles belonging to a bubble group due to bubble breakup and coalescence is equal to the death rate at high gas volumetric flux, (2) distributions of void fraction and bubble diameter are not affected by inlet bubble diameters except for the region close to the air diffuser, and (3) the elevation at which the bubble size distribution reaches the equilibrium state becomes lower as the gas volumetric flux increases.

CiNii Books

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

Air-water two-phase swirling flows in a downscaled model of a steam separator for a boiling water nuclear reactor have been measured while paying attention to the effects of pick-off-ring (POR) shape on separation performance. As a result, the following conclusions are obtained. (1) In an annular swirling flow, the ratio <I>W<SUB>s</SUB><SUP>*</SUP></I> of the separated liquid flow rate to the total liquid flow rate increases with <I>J<SUB>G</SUB></I> and does not depend on <I>J<SUB>L</SUB></I> and POR shape so much. (2) Separation performance becomes lower and does not depend on POR shape so much when the liquid film thickness becomes larger than the size of the gap between the barrel wall and the POR wall. The gap size should be determined so as to be smaller than the maximum film thickness. (3) The POR shape strongly affects the separation performance when the liquid film thickness is smaller than the gap size.

DOI： 10.3811/pmfr.3.67

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00322311785?from=CiNii

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/jfst.3.172

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Air-water swirling flows in a one-fifth model of a steam separator in a boiling water nuclear reactor are measured to obtain a database for modeling and verification of numerical methods for predicting swirling flows in the separator. Flow patterns, liquid film thicknesses, separated flow rates and the ratio <i>W_s</i>^* of the separated flow to the total liquid flow are measured using a high-speed camera, a laser focus displacement meter and flowmeters. Main conclusions obtained are as follows: (1) liquid transfer from droplets to liquid film is caused not only by droplet deposition but also by the collection of droplets on the vanes of the swirler, (2) <i>W_s</i>^* increases with the gas volume flux <i>J_G</i> and does not depend on the liquid volume flux <i>J_L</i> so much because a large centrifugal force caused by the swirler makes most of droplets in the gas core deposit on the liquid film before the separation and (3) a local peak appears in the axial distribution of film thickness, the position of which corresponds to the location where the droplet deposition caused by the centrifugal force has completed.

DOI： 10.1299/jpes.2.1120

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatmasstransfer.2006.12.033

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3327/jnst.44.894

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3811/pmfr.2.9

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3811/pmfr.2.55

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Shapes of single drops rising through infinite stagnant liquids under terminal conditions were measured using a high-speed camera for a wide range of fluid properties. Aspect ratios <i>E</i> and distortion factors γ of drops were evaluated from drop images. Effects of initial shape deformation, surfactants and viscosity ratio κ on <i>E</i> and γ were investigated. As a result, the following conclusions were obtained. (1) Initial shape deformation does not affect <i>E</i> and γ of single drops. (2) Addition of surfactants decreases <i>E</i> and breaks the fore-and-aft symmetry of a drop shape especially in systems of low Morton numbers <i>M</i>. (3) The Tadaki number <i>Ta</i> is the best dimensionless number among the Eötvös number <i>Eo</i>, the Weber number <i>We</i> and <i>Ta</i> for correlating <i>E</i> of drops, and an empirical correlation of <i>E</i> in terms of <i>Ta</i> was proposed for clean drops under the conditions of -11.6 ≤ log <i>M</i> ≤ -0.9, 1.5 × 10^-2 ≤ <i>Re</i> ≤ 8.5 × 10², 1.7 × 10^-2 ≤ <i>Eo</i> ≤ 9.3, 7.4 × 10^-3 ≤ <i>Ta</i> ≤ 3.6 and 0.1 ≤ κ ≤ 100. (4) The viscosity ratio κ does not affect <i>E</i> so much but influences γ. For κ > 1, γ decreases with increasing the drop diameter, that is, the front part of a drop is flatter than the rear part. On the contrary, the rear part is flatter than the front part when κ < 1. The fore-and-aft symmetry always holds for drops with κ ∼ 1.0. (5) Various drop shapes were presented as a database utilized for verification of numerical methods such as an interface tracking method and a boundary element method.

DOI： 10.1299/jfst.2.184

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Several experiments have reported that Departure from Nucleate Boiling (DNB) in a Pressurized Water Reactor (PWR) fuel assembly often takes place in upstream part of a grid spacer, and it was supposed that bubble accumulation induced by flow around an obstacle is one of reasons of the DNB inception. Hence, experiments were conducted to investigate the motion of small bubbles in high-speed flows in a vertical duct containing an obstacle. The bubble trajectories and averaged bubble distributions were measured by an image processing method. The experimental results indicated that small bubbles migrate toward the opposite wall of the obstacle near the upstream edge of the obstacle. The lateral translation of bubbles was larger than that of the liquid phase, which could be induced by the difference in inertia between bubbles and the liquid phase.

CiNii Books

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.v19.i3.40

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/18811248.2007.9711327

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1299/jfst.3.667

Web of Science

researchmap

Language：Japanese   Publisher：Atomic Energy Society of Japan  

DOI： 10.11561/aesj.2007s.0.236.0

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1299/jsmeb.49.1253

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Coalescence of two planar air bubbles in stagnant water filled in two parallel plates was experimentally investigated. To examine the effects of bubble wake on coalescence, the bubble diameter, initial vertical and horizontal distances between two bubbles were chosen as experimental parameters. The vertical distance <i>x</i> from the bubble release point, at which coalescence took place, was measured. The number of coalesced bubble pairs was counted for about 100 bubble pairs, and the coalescence probability was calculated as the ratio of the number of the coalesced bubble pairs to that of the total bubble pairs. With decreasing the bubble diameter or with increasing the initial distance between two bubbles, the mean vertical distance <i>x</i> increased and the coalescence probability decreased. There was a strong correlation between the distribution of coalescence probability and that of bubble wake velocity, i.e. the wake structure does play a significant role in the bubble coalescence process and affects the coalescence probability.

DOI： 10.1299/jfst.1.94

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Terminal velocities of single drops rising through infinite stagnant liquids under wide ranges of fluid properties were measured to examine the effects of initial shape deformation, surfactants and the viscosity ratio. As a result, the following conclusions were obtained: (1) the terminal velocity <i>V_T</i> of a drop is not affected by initial shape deformation due to strong viscous damping of shape oscillation, (2) the drop drag coefficient <i>C_D</i> is a function of the drop Reynolds number <i>Re</i>, the viscosity ratio κ and surfactant concentration, (3) surfactants increase <i>C_D</i> and the influence of surfactants on <i>C_D</i> becomes weaker as κ increases, which is consistent with the Levich's drag model, (4) the effect of κ on <i>C_D</i> can be evaluated by the factor in the Levich's model, [(2+3κ)/(1+κ)], even at intermediate drop <i>Re</i> numbers, and (5) the combination of the Levich's model and Schiller & Nauman's correlation gives good estimation of <i>C_D</i> of single drops in clean and fully contaminated systems under the conditions of -11.6 <log₁₀<i>M</i> < -0.9, 1.7×10^-1 < <i>Re</i> < 2×10², 1.7×10^-2 < <i>Eo</i> < 12.1 and 0.1 < κ < 100.

DOI： 10.1299/jfst.1.72

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.3811/pmfr.1.65

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In the present study cavitation in a two-dimensional (2D) nozzle and the injected water jet were visualized using an ultra high-speed camera. As a result, the following conclusions were obtained: (1) The behavior of cavitation in the 2D nozzle and liquid jet agreed qualitatively with the previous observations of cylindrical nozzles. (2) When the cavitation number σ was 1.18, the inception of small cavitation bubbles was observed near the nozzle inlet apart from the side wall. (3) The number of cavitation bubble clouds increased with decreasing of σ (0.75&ge;σ<1.18), and the streamwise length of the cavitation region increased toward the middle of the nozzle (developing cavitation). The bubble clouds were clearly observed to recirculate in the separated boundary layer. In the case a wavy jet was observed with no significant effects of cavitation on liquid jet atomization. (4) With a slight decrease of σ from 0.75, the cavitation region suddenly extended to the nozzle exit (super cavitation). The shape of the cavitation region near the inlet became smooth, which imply the formation of a long cavitation bubble near the inlet. At the downstream half of the nozzle, clouds of cavitation appeared and collapsed intermittently within the nozzle. In the case atomization was promoted to form spray with ligaments and droplets.

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Cavitation and internal flow in the nozzle of a liquid injector are known to affect the atomization of a discharged liquid jet. In order to obtain the knowledge on the mechanism how cavitating flow in a nozzle enhances the liquid jet atomization, liquid velocity distributions of cavitating flows in a two dimensional transparent nozzle were measured using a Laser Doppler Velocimetry (LDV) system. As a result, the following conclusions were obtained: (1) The inception of cavitation occurs near the outer edge of the separated boundary layer (SBL), where the mean local velocity takes the highest value and the mean pressure is lower than the vapor saturation pressure. (2) When the cavitation number σ&ge;0.78 (No Cavitation or Developing Cavitation), the reattachment of SBL occurs in the middle of the nozzle. A large velocity fluctuation, which appears in and just downstream of SBL, decreases near the nozzle exit. This may be the reason of the wavy jet. (3) When σ&ge;0.65 (Super Cavitation), the lateral flow from the core region toward the side walls just upstream of the nozzle exit may be the major cause of the increase in spray angle and a drastic promotion of liquid jet atomization. The strong turbulence just upstream of the exit may also play a role on the formation of ligaments at liquid jet interface.

CiNii Books

researchmap

Language：Japanese   Publisher：The Visualization Society of Japan  

To verify the validity of a numerical method to predict multi-phase dispersed flows of which the density varies with fluid temperature and solute concentration, solute concentration and velocity distributions of a salt water flow were measured using an imaging technique. The aspect ratio and rising velocity of a single drop in a density stratified salt water were also measured. Calculated results of these flows agreed well with the measured results.

DOI： 10.3154/jvs.26.Supplement1_301

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1115/ICONE14-89332

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.v18.i1.40

Scopus

researchmap

Publisher：Atomic Energy Society of Japan  

DOI： 10.11561/aesj.2006f.0.258.0

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ijheatfluidflow.2004.02.001

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.70.356

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1615/MultScienTechn.v16.i4.40

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/18811248.2003.9715416

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/S0301-9322(03)00030-2

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3327/jnst.40.136

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1142/S0217979203017308

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.69.2214

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.69.2208

Scopus

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

DOI： 10.1016/S0301-9322(03)00030-2

Scopus

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Sufficient knowledge of turbulence modification is indispensable to understand the turbulence structure and to develop a turbulence model in gas-liquid two-phase bubbly flow in vertical pipes. There is, however, little information on the interaction between shear-induced turbulence and bubbles in the near wall region, whereas many researches have been carried out on the turbulence properties in gas-liquid bubbly flow in a vertical pipe. In this study, we measured liquid velocity in the near wall region where the shear-induced turbulence is generated and interacts with bubbles. The measured result indicated that (1) bubbles increase the gradient of mean liquid velocity and therefore the shear-induced turbulence is enhanced in the near wall region, and (2) bubbles break up the developed large-scale shear-induced eddy and obstruct the transfer of turbulence energy from the near wall region to the core region.

DOI： 10.1299/jsmemecjo.2003.3.0_267

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1115/FEDSM2002-31148

Scopus

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A three-dimensional one-way Bubble Tracking Method has been proved to give good predictions for the spatial evolution of flow pattern, mean void fraction, void fluctuation, mean pressure drop and pressure drop fluctuation in developing bubble flows in vertical pipes. In this study, the spatial evolution of radial developing bubble flow. As a result, it is confirmed that the method gives good predictions of local void fractions, provided that bubble size distributions at an inlet were available.

DOI： 10.1299/jsmemecjo.2002.3.0_325

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.68.2050

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1115/FEDSM2002-31150

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1080/18811248.2001.9715037

Web of Science

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Sufficient knowledge of Reynolds stress is indispensable to understand the turbulence structure and to develop a turbulence model in gas-liquid two-phase bubbly flow. There is, however, little information on the Reynolds shear stress as well as radial and azimuthal turbulence intensities, whereas many researches have concerned on the axial turbulence intensities in a gas-liquid bubbly flow in a vertical pipe. In this study, we utilized a pipe made of fluoro carbon which has the same refractive index with water, and which enabled us to measure the two velocity components simultaneously using LDV in air-water two-phase bubbly flow in vertical pipes. The measured result indicated that all the components of Reynolds stress are affected by the presence of bubbles. Bubble-induced agitation of a liquid velocity field was particularly prominent under a laminar flow condition. Turbulence enhancement as well as suppression due to the presence of bubbles was observed.

DOI： 10.1299/jsmeptec.2001.0_393

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publisher：THE JAPANESE SOCIETY FOR MULTIPHASE FLOW  

Three-phase flows are encountered in air-lift pumps, preheaters and reactors, and other industrial plants. It is necessary to clarify not only macroscopic characteristics such as pressure drops and volume fractions of each phase but also local characteristics such as spatial distnbutions of local volume fractions and local velocities of each phase. In the present review, measurement techniques of volumetric fluxes and volumetric fractions of each phase, radial distributions of gas and solid volume fractions and liquid velocities were described for the three-phase bubbly flow. Those of length and velocities of large bubble liquid slug and film thickness of large bubble were also described for the three-phase slug flow Furthermore, application of measurement techniques for two-phase flows to three-phase flows were examined.

DOI： 10.3811/jjmf.14.270

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00152027313?from=CiNii

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/kikaib.66.652_3071

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.4271/970631

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/ppsc.19940110204

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Web of Science

researchmap

Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)   Publisher：日本流体力学会  

researchmap

Language：Japanese   Publishing type：Lecture material (seminar, tutorial, course, lecture, etc.)  

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A measurement method of local instantaneous velocity gradients in turbulent flows are required to evaluate turbulence kinetic energy (TKE) budget. Spatiotemporal Filter Velocimetry (SFV) is therefore applied to evaluation of TKE budget by coupling with a molecular tagging method using photobleaching reaction. Measurements are carried out not only for single-phase turbulent flow but also for bubbly flows with two different bubble diameters to examine effects of bubble diameter on the velocity distribution and TKE budget. As a result, the following conclusions are obtained: (1) Effect of bubble diameter on the distribution of axial mean velocity is weak under the fixed void distribution and the fixed interaction forces between the phases. (2) Effect of bubble diameter on TKE budget is not so large in the bubbly flows whereas the presence of bubbles tend to reduce the magnitudes of the production and diffusion rates.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is important in design and development of reactor cores to increase knowledge of turbulent flows in rod bundles. In this study, we therefore measured velocity in single-phase and bubbly flows by installing a small LDV probe into a rod of a 2x2 rod bundle. The diameter and the pitch of the rods were 10 and 13 mm, respectively. The liquid volume flux was 1 m/s, and the gas volume flux in the bubbly flow was 0.08 m/s. The local time-averaged velocity and turbulent intensity were obtained from 10,000 instantaneous velocities at each measurement point. As a result, the following conclusions were obtained: (1) The distribution of liquid velocity in the bubbly flow is flatter than that in the single-phase flow, and the velocity gradient near the wall increases due to the presence of bubbles. (2) Local wall shear stress on the rod wall depends on the azimuthal localtion, and the distributions of dimensionless liquid velocities near the wall in inner subchannel agree with the universal dimensionless mean velocity profile of wall turbulence.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (other)   Publisher：日本機械学会流体工学部門  

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Spatial filter velocimetry (SFV) based on spatial filtering of time-series particle images proposed by Hosokawa and Tomiyama is applied to a planar bubble plume to examine its applicability to simultaneous measurement of bubble and liquid velocities. The edge detection process is added in the SFV processing to reduce the size of image pattern and to obtain accurate bubble velocity. Bubble regions in the recorded images of the planer bubble plume are detected by using a labeling process, and the particle and bubble images are generated by masking the bubble region and by inversing the bubble region, respectively. Then, SFV processing is applied to particle and bubble images to obtain liquid and bubble velocities, respectively. The measured results clearly demonstrate the potential of SFV for simultaneous measurements of liquid and gas velocities in two-phase flows.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Presence of interface in gas-liquid two-phase flow makes it difficult to measure liquid velocity using LDV at a high void fraction. In the present study, we have developed small LDV optics to avoid the difficulty in optical access by submerging the LDV probe into a flow field. The diameter of the probe is 7 mm. The developed system is applied to bubbly flow in a bubble column to examine its applicability to bubbly flow at a high void fraction. Comparisons with a conventional LDV system show that the accuracy and reliability of the developed system are the same level as the conventional system, and that the developed system can measure liquid velocity in bubbly flow at high void fractions, in which the conventional LDV cannot measure the liquid velocity. The measured data show that the axial mean velocity and turbulence intensity increase with the gas volumetric flux J_G not only at low JG but also at high J_G.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Although area-averaged void fractions in subchannels have been measured frequently in literatures, distribution of local void fraction in a rod bundle have been rarely reported. Little is also known on bubble motion in a rod bundle. Distributions of local void fraction and bubble velocity in a 4x4 rod bundle were, therefore, measured using a conductance probe in this study. Liquid velocity was also measured using LDV. Experimental results showed that the distributions of the void fractions in the inner and side subchannels depend not only on lift force acting on bubbles but also on geometrical interaction between the bubble and the rod wall. The relative velocity between bubbles and liquid phase in the subchannel possesses non-uniform distribution over the cross-section. This is caused by increase in drag force acting on bubbles due to bubble deformation induced by interaction between the bubbles and the rod wall.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Validation of turbulence models is not an easy task mainly due to lack of experimental data on turbulent flows in rod bundles. In this study, we therefore measured distributions of velocity and turbulence intensities of water flow in a 2x2 rod bundle by using a stereoscopic PIV system. The diameter and pitch of the rods were 20 and 25 mm, respectively. Area-averaged velocity was 2 m/s. Local time-averaged velocity and turbulent intensities were obtained from 10,000 instantaneous velocities at each measurement point. Experimental results showed that horizontal components of turbulence intensity in the cross-section are anisotropic near the rod gap. Since eddies larger than the gap width cannot exist in the rod gap, the turbulence spectrum takes low values in the rod gap compared with center region of subchannel. To the contrary, difference in the turbulence spectrum of eddies smaller than the gap width is small between the rod gap and the center of subchannel.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Improvement of steam separators in ABWR is required to decrease pressure drops at high steam qualities without degrading the separation performance. In this study, shapes of the swirler and 1^<st> pick-off ring (POR) were modified to reduce the pressure drop, and experiments using a one-fifth scale model of the separator were carried out to evaluate its performance. Experimental data showed that the modifications successfully reduce the pressure drop and carry-under (CU) in the separator without degrading the separation performance.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese  

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Endoscopic PIV has been developed to measure flows in opaque equipment. It is however difficult to measure velocities near the edge of the field of view in the endoscopic PIV due to the Lagrangian nature of PIV. The authors developed an Eulerian velocimetry, that is, spatial filter velocimetry (SFV) to realize the simultaneous multipoint measurement of velocity with a high spatial resolution and high accuracy. In this study, we visualized natural convection of water in a pan heated by a cooking stove using a high-speed video camera with a borescope. The velocity distribution in the field of view of the borescope is evaluated by SFV to examine applicability of SFV to measurement of a velocity distribution from the borescope images. The experimental results indicated that SFV can measure the velocity accurately at arbitrary multiple points in the filed of view. The results also demonstrated the high applicability of SFV to the whole field measurement of velocity in the field of view of endoscopic visualization.

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Most of unintrusive velocimetry techniques utilize fine tracer particles to measure fluid velocity. The addition of tracer particles in multiphase flows induces not only errors due to their imperfect followability but also flow disturbance due to their accumulation at gas-liquid interface. Molecular tagging velocimetry (MTV) is one of recommendable methods to remove these difficulties. Some applications of MTV are introduced to demonstrate its advantages.

CiNii Books

researchmap

Language：Japanese  

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

Language：Japanese  

A molecular tagging velocimetry based on photobleaching reaction was applied to turbulent bubbly flows with sub-millimeter bubbles in a vertical square duct to examine the applicability of the κ-ε models to the bubbly flows. The conclusions obtained are as follows: (1) The κ-ε models can reasonably evaluate the production rate of turbulence kinetic energy (TKE) in bubbly flows. (2) Bubbles agitate the liquid flow and enhance the diffusion rate of TKE. The enhancement of the diffusion due to bubbles has different characteristics from the diffusion enhancement due to shear-induced turbulence, and the κ-ε models cannot evaluate the enhancement of diffusion rate due to bubbles in the near wall region. (3) The κ-ε models give not so bad predictions for the production, diffusion and dissipation rates of dissipation rate of TKE.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Since the conservation equation of turbulence kinetic energy (TKE) involves correlations among local instantaneous gradients of fluctuating velocities, it is indispensable to measure the velocity gradients as well as the velocity components. The authors developed a molecular tagging method using photobleaching (PB-MTV), which can measure not only velocity but also its gradient by making use of the translation and deformation of a tag. In this study, we applied the PB-MTV to turbulent bubbly flows in a square duct. The experimental results indicate that position of turbulence transition between viscous sub-layer and log region shifts toward the wall by the presence of bubbles. The presence of bubbles increases not only the production rate but also the dissipation rate of TKE. The enhancements in the production and the dissipation rates are well correlated with the local void fraction.

CiNii Books

researchmap

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

CiNii Books

researchmap

J-GLOBAL

researchmap

Language：Japanese  

CiNii Books

researchmap

Language：Japanese  

CiNii Books

researchmap