Publishing type：Part of collection (book)  

Direct diamond deposition on a steel surface has been considered very difficult. Recently, we found that high-quality diamond films can be deposited on the surface of stainless-steel X5CrNi 18-10 by drilling multiple regularly arranged pits without interlayers or seeding. The following two hypotheses (A) and (B) can be considered as the reason why a high-quality diamond film can be deposited: (A) unoxidized Cr and Ni exposed to the stainless-steel X5CrNi 18-10 surface prevent carbon diffusion into interior of the stainless-steel, resulting diamond core generation, (B) Surface geometry with regular roughness contributes to stress relaxation and delamination prevention. In the present study, those hypotheses have been examined by quantum chemistry calculation and experimental. For the quantum chemistry calculation, energy barrier and kinetic energy for a carbon atom intrudes into a model cluster has been calculated with an ab-initio computational chemistry software package, Gaussian. The calculation result has supported hypothesis (A). For the experiment, X5CrNi 18-10 stainless-steel substrates with different surface characteristics are prepared by using various mechanical machining methods and used in the direct deposition process for diamond with in-liquid plasma CVD. The experimental result has supported both hypothesis (A) and (B).

DOI： 10.4028/p-vf0NZL

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

Two versus 1 venous reconstruction is sometimes required for Hepato-Biliary-Pancreatic and Transplantation surgery. V-shape venoplasty is considered to be useful knack of unification method during 2 versus 1 venous reconstruction in clinical practice. The usefulness of V-shape unification venoplasty was proven by the present computational fluid dynamics study.

DOI： 10.1002/jhbp.1280

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Institute of Energy  

Steel coated with diamond film is excellent material specifically for cutting tools. However, direct diamond deposition has been considered difficult. In the present study, a stainless steel surface was mechanically processed to directly deposit diamond on it. Diamond film was rarely obtained when the steel surface was rasped with sandpaper, metal file, or ground with a flat drill. In most cases, amorphous carbon was deposited on the surface. On the other hand, high-quality diamond was often deposited when regularly arranged pits were created on the surface using a drill. In this case, the diamond was deposited on the lips of the pits and the flat (nonprocessed) areas between (rather than on the inside of) the pits. The quality of diamond film obtained in the present work is the best reported for direct diamond chemical vapor deposition (CVD) on steel. It is an important discovery that high-quality diamond film can be directly deposited on steel surfaces via simple mechanical surface processing without interlayer or seeding.

DOI： 10.3775/jie.101.147

CiNii Research

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Ultrasonic welding is a processing technology that can instantly fuse and join thermoplastic resins by applying minute amounts of ultrasonic vibration and pressure. The present study demonstrates that the frictional force or pressure caused by ultrasonic welding can cause cellulose decomposition without a saccharifying enzyme or catalysts. Ultrasonic waves of 19.5 kHz were irradiated downward on samples using a horn-type transducer. The cellulose specimens were composed of 15 – 105 stacked sheets of filter paper with high cellulose content, a sheet of cotton, and a sheet of hemp. The high frictional forces resulting from direct contact of cellulose with the ultrasonic horn tips decomposed the saccharides within a short time to produce glucose. Cellulose is decomposed into glucose through hydrolysis in an enzyme-free environment by ultrasonic irradiation, but then it is further decomposed into 5-hydroxymethylfurfural, furfural, and other compounds via a dehydration reaction caused by an increase in temperature of the reaction field from continuous ultrasonic irradiation. Glucose could be obtained from the cellulose without using an enzyme through ultrasonic welding. The result of decomposing cellulose, cotton, and hemp by this method revealed that a yield of 1.2% glucose could be obtained by decomposing filter paper.

DOI： 10.1016/j.ijft.2022.100137

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

© 2019 Trans Tech Publications Ltd, Switzerland This study was performed to improve the adhesiveness of a diamond-like carbon (DLC, a-C:H) layer film with an a-SiC interlayer. In previous studies, an a-SiC/DLC layer film was formed and changes in the DLC film structure and hardness caused by the thickness of the a-SiC layer were examined. After the a-SiC interlayer thickness increased and the G-peak position shifted to a lower frequency, the peak began shifting to higher frequencies. The G-peak position reached a minimum frequency at a film thickness of approximately 0.3 µm. In contrast, as the thickness of the a-SiC interlayer increased, the FWHM of the G-peak position increased almost monotonically and the number of sp3 bonds also increased. As the interlayer thickness increased, the hydrogen content in the DLC film increased, and then began decreasing, with the interlayer film thickness exhibiting a local maximum at approximately 0.3 µm. As for the DLC film hardness, a correlation between the hydrogen content and half width of the G-peak position was observed. When the hydrogen content was ≤40 at%, a positive correlation with the FWHM (G) was observed, and when the hydrogen content was 40 at% or above, a negative correlation with FWHM (G) was found. The adhesiveness of the DLC film and substrate was improved by forming an a-SiC thin film as an interlayer. The effects of the a-SiC thin film on DLC film quality were determined.

DOI： 10.4028/www.scientific.net/KEM.825.99

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

A relationship between diamond synthesis and hydrogen production in in-liquid plasma method have been investigated. Approximately 60% energy can be recovered by collecting hydrogen gas made by ingredient solution decomposition. The relationship is trade-off. When higher energy is used to maintain the substrate temperature, the hydrogen production rate gets faster, but the diamond synthesis rate gets slower. To increase diamond synthesis rate, a method should be established which maintains the substrate temperature by lower energy and generates less hydrogen gas.

DOI： 10.4028/www.scientific.net/KEM.825.77

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

Diamond crystals are successfully synthesized by irradiating DC arc plasma jet to the substrate set in a methanol solution. It is the important procedure to preheat the substrate by inert Ar plasma jet before introducing the methanol solution gas to the plasma jet gun. The effects of two experimental conditions, the incident power and the substrates, are investigated. In the case of the Si substrate, cubic crystalline diamond grains of same size are synthesized at the plasma power of 470W. High speed hetero epitaxy is expected by using this method. In the case of the tungsten carbide substrate, diamond crystals and carbon nanotubes are simultaneously synthesized at the plasma power of 260W. The catalytic effect of Co binder in the substrate may cause the chemical reaction of the nanotube synthesis.

DOI： 10.4028/www.scientific.net/KEM.825.71

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE INC  

The purpose of this study is to synthesize diamond onto Si, Cu, and Fe (SUS632J2) substrates and to analyze the effect of carbon diffusion on their surfaces. Diamond was synthesized using the in-liquid microwave plasma chemical vapor deposition (IL-MPCVD) as a novel method for synthesizing diamond on various base materials. The IL-MPCVD method is superior one due to its efficiency in terms of cost, space and speed as compared to a conventional gas phase microwave plasma CVD (MPCVD). Microwaves of 2.45 GHz generated plasma in a solution which was comprised of methanol: ethanol (M:E= 97:3). Evaluation of deposited diamond films was done by a Scanning Electron Microscope (SEM) and Raman spectroscopy. Results shows that the IL-MPCVD method can form diamond films on Cu, Si and Fe substrates. The minimum time of film formation of Cu, Si and Fe are 2.5, 3.5 and 5 min, respectively. The material that forms carbide layers such as Si is a better substrate to form diamond film by the IL-MPCVD than other metal substrates such as Cu and Fe. Synthesizing diamond directly on the Fe substrate results in poor quality layers. The effect of carbon diffusion influences diamond film nucleation and diamond growth. In order to alleviate the carbon diffusion and improve the quality of the diamond film on the Fe substrate, Si has been sputtered on the Fe substrate as an interlayer. It is found that the diamond film can be formed on a Fe substrate using a Si interlayer and that heat treatment and thickening the interlayer improve its quality. (C) 2017 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.precisioneng.2017.04.003

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Turbomachinery Society of Japan  

Wall pressure measurements and flow visualization were conducted for a 90 degree elbow with an axis curvature radius the same as its inner diameter (125 mm). Reynolds numbers 320,000 and 500,000, based on the inner diameter and bulk velocity, were examined. A deflected inflow, having an almost constant velocity slope and a faster velocity at the inside, was introduced. Ensemble averaged pressure distributions showed that no difference of normalized pressure could be found in both the Reynolds number cases. Power spectral density functions of pressures exhibited that the fluctuation having the Strouhal number (based on the inner diameter and bulk velocity) of 0.6 existed in the downstream region of the elbow, which was 0.1 larger than that of the uniform inflow case [1]. Results of numerical calculations qualitatively coincided with the experimental ones.

DOI： 10.5293/IJFMS.2017.10.1.076

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

© 2017 Trans Tech Publications, Switzerland. The most progress towards a practical method of fusing municipal waste incineration ash has been in the use of a plasma jet that employs arc discharge, a form of thermal plasma. However, a remaining problem is that stable plasma generation is prevented by melting of the nozzle of the plasma-jet torch by the high-Temperature plasma flow. With the objective of developing high-speed fusion treatment for waste materials using an in-liquid plasma jet, basic research was conducted on plasma stability and the durability of plasma-jet torches, including electrodes and nozzles. Basic plasma jet characteristics such as the discharge voltage, current, and power value at the time of plasma jet generation were investigated experimentally. The relationship between the temperature distribution near the tip of a plasma jet torch and electrode damage was investigated by fluid-heat coupled analysis using the finite element method.

DOI： 10.4028/www.scientific.net/KEM.749.76

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

© 2017 Trans Tech Publications, Switzerland. Currently, novel method to synthesize diamond film on material substrate called as in-liquid microwave plasma CVD (IL-MPCVD) has been achieved. It has been studied and improved in addition expected as new method instead of conventional gas phase microwave plasma CVD (MPCVD). The purpose of this study is to synthesize single crystal diamond using IL-MPCVD in high speed deposition. The experimental conditions, methanol was poured in to the reactor. Each of diamond particles (100) and (111) was embedded on the stainless steel substrates (SUS632J2). It was mounted to the substrate holder of in-liquid plasma equipment and installed on the top cover. The distance between the tip of the electrode and the substrate was kept to 1.5mm. A microwave of 2.45GHz was irradiated into the quartz glass tube reactor from the rectangular cavity resonator with 4 mm diameter tungsten electrode and the plasma was generated at its tip. The microwave was adjusted in appropriate power to maintain a certain substrate temperature. Diamond films were evaluated by Raman spectroscopy, Scanning Electron Microscope (SEM) and Laser Microscope (LM). As a result, the best orientation for epitaxial growth was found to be (100) which have film growth gradually and smooth surface. Whereas (111) face has polycrystalline film with irregularity growth and rough surface. The remaining H and C after CO synthesis satisfying H/C>20 is necessary to synthesized diamond using IL-MPCVD. The deposition rate was about 32m/h when both single crystal and polycrystalline diamond film were synthesized.

DOI： 10.4028/www.scientific.net/KEM.749.211

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

© 2017 Trans Tech Publications, Switzerland. Diamond-like-carbon (DLC) films are promising as coating materials. Ion plating, an excellent method in terms of adhesiveness, step coverage, and deposition rate, can form not only pure metal films but also oxide films, nitride films, and carbonized films. In this study, which aimed to form a DLC film with good adhesiveness and a diamond crystal structure, a DLC film, with a SiC interlayer formed by ion plating with introduction of tetramethylsilane (TMS), was formed. It was experimentally revealed that as the interlayer thickness increases, the crystal structure in the DLC film becomes more diamond rich, and the adhesiveness of the DLC film and substrate is thereby improved.

DOI： 10.4028/www.scientific.net/KEM.749.70

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

© 2017 Trans Tech Publications, Switzerland. High-speed synthesis of the carbon nanotubes in liquid is introduced. The conventional method for synthesizing carbon nanotubes is generally known as gas-phase chemical-vapor deposition (CVD). With that method, carbon nanotubes of high purity can be synthesized, but the synthesis rate is low. Even though the synthesized carbon nanotubes are excellent materials, they cannot be used in large quantities. Accordingly, in this study, single-wall carbon nanotubes (SWCNTs) are synthesized by "in-liquid" CVD. Since the molecular density of a liquid is much higher than that of a gas and the liquid has a cooling effect, performing CVD in a liquid can provide a high-speed growth rate of CNTs on substrate materials. A silicon substrate on which cobalt micro particles are deposited as the catalyst was used. Electrical-resistance heating was used for growing carbon nanotubes in pure ethanol. The synthesized nanotubes were analyzed by scanning electron microscope, transmission electron microscope, and Raman spectroscopy. The results of these analyses indicate that SWCNTs were successfully synthesized over a wide area of the substrate surface. By investigating the synthesized carbon nanotubes under varied experimental conditions (such as pressure and substrate surface roughness), it is shown that surface roughness of the substrate and the bubble behavior are related to the synthesis mechanism of the CNTs.

DOI： 10.4028/www.scientific.net/KEM.749.217

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Language：Japanese   Publisher：公益社団法人 精密工学会  

本研究の目的は高純度単層カーボンナノチューブを高速形成することである．気相よりも分子密度の高い液相における液中熱化学気相蒸着(CVD)法での合成について調査し考察した．膜厚と合成温度の関係，触媒金属の種類によるCNT合成影響，溶液の構成元素数の違いによる影響を考察した．膜厚と温度の関係，適切な触媒金属，液中CVD法でのCNT合成手法の確立がなされた．

DOI： 10.11522/pscjspe.2017A.0_433

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Language：Japanese   Publisher：The Japan Society for Precision Engineering  

Diamond was synthesized using the in-liquid microwave plasma chemical vapor deposition (IL-MPCVD) as a novel method for synthesizing diamond on various base materials. Microwaves of 2.45 GHz generated plasma in a solution which was comprised of methanol: ethanol (M:E = 97:3). Evaluation of deposited diamond films was done by a Scanning Electron Microscope (SEM) and Raman spectroscopy. Results shows that the IL-MPCVD method can form diamond films on Cu, Si and Fe substrates. The minimum time of film formation of Cu, Si and Fe are 2.5, 3.5 and 5 minutes, respectively. The material that forms carbide layers such as Si is a better substrate to form diamond film by the IL-MPCVD than other metal substrates such as Cu and Fe. The effect of carbon diffusion influences diamond film nucleation and diamond growth. In order to alleviate the carbon diffusion and improve the quality of the diamond film on the Fe substrate, Si has been sputtered on the Fe substrate as an interlayer. It is found that the diamond film can be formed on a Fe substrate using a Si interlayer and that heat treatment and thickening the interlayer improve its quality.

DOI： 10.11522/pscjspe.2017A.0_435

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

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Stagnation of a cold plasma streaming to the center or axis of symmetry via an expanding accretion shock wave is ubiquitous in inertial confinement fusion (ICF) and high-energy-density plasma physics, the examples ranging from plasma flows in x-ray-generating Z pinches [Maron et al., Phys. Rev. Lett. 111, 035001 (2013)] to the experiments in support of the recently suggested concept of impact ignition in ICF [Azechi et al., Phys. Rev. Lett. 102, 235002 (2009); Murakami et al., Nucl. Fusion 54, 054007 (2014)]. Some experimental evidence indicates that stagnation via an expanding shock wave is stable, but its stability has never been studied theoretically. We present such analysis for the stagnation that does not involve a rarefaction wave behind the expanding shock front and is described by the classic ideal-gas Noh solution in spherical and cylindrical geometry. In either case, the stagnated flow has been demonstrated to be stable, initial perturbations exhibiting a power-law, oscillatory or monotonic, decay with time for all the eigenmodes. This conclusion has been supported by our simulations done both on a Cartesian grid and on a curvilinear grid in spherical coordinates. Dispersion equation determining the eigenvalues of the problem and explicit formulas for the eigenfunction profiles corresponding to these eigenvalues are presented, making it possible to use the theory for hydrocode verification in two and three dimensions.

DOI： 10.1063/1.4948492

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_659

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>In this study, the synthesis of single-wall carbon nanotubes (SWCNT) using in-liquid CVD method is attempted. Si substrate on which Co micro particles are deposited as the catalyst is used. Electrical resistance heating method is used for glowing carbon nanotubes in pure ethanol. The synthesized materials are analyzed by scanning electron microscope, transmission electron microscope and Raman spectroscopy. As a result, the synthesis of SWCNT was successful on a wide area of the substrate surface. By investigating the synthesized carbon nanotubes changing experimental conditions such as pressure, substrate surface roughness and others, it is cleared that surface roughness of the substrate and the bubble behavior are related to the synthetic mechanism of carbon nanotubes.</p>

DOI： 10.1299/jsmeted.2016.G114

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Based on Guderley's self-similar solution, stability of spherical converging shock wave is studied. A rigorous linear perturbation theory is developed, in which the growth rate of perturbation is given as a function of the spherical harmonic number l and the specific heats ratio gamma. Numerical calculation reveals the existence of a gamma-dependent cut-off mode number l(c), such that all the eigenmode perturbations for l &gt; l(c) are smeared out as the shock wave converges at the center. The analysis is applied to partially spherical geometries to give significant implication for different ignition schemes of inertial confinement fusion. Two-dimensional hydrodynamic simulations are performed to verify the theory. (C) 2015 AIP Publishing LLC.

DOI： 10.1063/1.4923437

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

This paper is intended to validate the numerical simulation tool, which is Unsteady Reynolds Averaged Navier-Stokes equation (U-RANS) approach with the Reynolds Stress Model using a commercial computational fluid dynamics code, by applying to the flow through a single short-elbow in the 1/10 and 1/3 scale water experiments simulating the Japan Sodium-Cooled Fast Reactor (JSFR) hot-leg piping. An additional objective of this paper is to investigate the effect of outlet condition at which the coolant overflows a partition wall in the upper part of an intermediate heat exchanger in the JSFR design. The numerical results were in good agreement with the 1/10 and 1/3 scale experimental data indicating time-averaged velocity distributions, flow field visualization, and power spectral densities of pressure fluctuation. These comparisons can conclude that the U-RANS numerical simulation tool was validated with its applicability to a single short elbow flow. The numerical simulation has also shown that the unsteady flow fields in the short elbow flow, which was characterized by a cyclic secondary flow and the subsequent horseshoe vortex. In this study, the effect of the outlet condition was also examined through the numerical simulation. At the outlet of the pipe, the simulation modeled the partition wall in the upper part of the intermediate heat exchanger, which has never been simulated in the experiments. The numerical simulation results were compared between with and without the intermediate heat exchanger at the pipe outlet in terms of the time-averaged velocity distribution, pressure fluctuation power spectral density, and so on. In the result, no significant difference between them was observed, so that it can be said that the effect of the outlet condition is negligibly small.

DOI： 10.1115/AJKFluids2015-03510

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DOI： 10.1299/jfst.2014jfst0055

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EPL ASSOCIATION, EUROPEAN PHYSICAL SOCIETY  

A novel compression scheme is proposed, in which hollow targets with specifically curved structures initially filled with uniform matter, are driven by converging shock waves. The self-similar dynamics is analyzed for converging and diverging shock waves. The shock-compressed densities and pressures are much higher than those achieved using spherical shocks due to the geometric accumulation. Dynamic behavior is demonstrated using two-dimensional hydrodynamic simulations. The linear stability analysis for the spherical geometry reveals a new dispersion relation with cut-off mode numbers as a function of the specific heat ratio, above which eigenmode perturbations are smeared out in the converging phase. Copyright (C) EPLA, 2012

DOI： 10.1209/0295-5075/100/24004

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

Laser Doppler Velocimetry (LDV) measurements in a 90 degree elbow of which the curvature radius coincides with its inner diameter were examined for the cases of inflow from a long pipe, short pipe and swirl generator. Ensemble averaged flow distribution at the Reynolds number of 320000 based on the inner pipe diameter and bulk velocity shows that shortening the upstream pipe length to 4.9<I>D</I> from 10<I>D</I> induces the flow separation downstream of the elbow. Detailed observation suggests that shortening upstream pipe weakens the Prandtl's secondary flow of the first kind. Our swirl generator induced a swirling inflow with the non-dimensional angular momentum of 0.12 based on the inner pipe diameter and bulk velocity. The circumferential velocity distribution formed a shape like a Rankine combined vortex at the elbow inlet, and the accelerated axial velocity was observed at the vortex center. The axial velocity distribution however was found to be almost the same as that of the non-swirl inflow case in the latter half of the elbow. Frequency analyses showed that the Strouhal number by vortex shedding from the boundary layer occurring at the inner side of the elbow become 0.5, except for 0.6 in the case of the long pipe. The change of the Strouhal number is probably related with the boundary layer width and the local flow velocity.

DOI： 10.1299/jfst.7.315

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

LDV measurements in a 90 degree elbow, of which curvature radius coincides with the diameter have been conducted for cases of developed inflow, undeveloped inflow, swirling inflow, and deflected inflow that became faster at the inside. This paper especially focuses on a result of the deflected inflow, comparing with a result of the undeveloped inflow. The result shows that the deflected inflow reinforces a convex velocity distribution occurring near the curvature inside in the downstream region, concluding that the deflected inflow promotes the secondary flow of Prandtl&#039;s first kind in the elbow. Frequency analyses of axial flow fluctuations show that the dominant frequency can be seen in the downstream of the elbow even in the deflected inflow case. However its Strouhal number increases to 0.6 from 0.5, that is for the short pipe case. Results of frequency analyses are also shown for other cases that we have been examined. Dominant Strouhal numbers in most of the cases become 0.5, except for 0.6 in cases of the developed and deflected inflow. This frequency shift might be related with the boundary layer size and the local flow velocity, since the corresponding fluctuation is caused by vortex shedding from the boundary layer at the elbow inside.

DOI： 10.1299/kikaib.78.1383

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

A study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius (&quot;short-elbow&quot;) has been conducted. Flow-induced vibration in the short-elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this paper, unsteady flow characteristics in the JSFR short-elbow pipe related to the large-scale eddy motion were estimated based on knowledge from existing studies for curved pipes and scaled water experiments and numerical simulations for the JSFR hot-leg piping.

DOI： 10.1299/kikaib.78.1392

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

This paper describes the current status of flow-induced vibration evaluation methodology development for primary cooling pipes in the Japan sodium-cooled fast reactor (JSFR), with particular emphasis on recent research and development activities that investigate unsteady elbow pipe flow. Experimental efforts have been made using 1/3-scale and 1 /10-scale single-elbow test sections for the hot-leg pipe. The 1/10-scale experiment simulating the hot-leg pipe indicated no effect of pipe scale in comparison with the 1/3-scale experiment under inlet-rectified-flow conditions. The next 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 deflected at the downstream from the elbow, the experiment clarified a less significant effect of swirl flow on pressure fluctuation onto the pipe wall. An additional experiment was intended to study the effect of elbow curvature. The experiments with water revealed no clear flow separation in a larger curvature elbow case than that of the JSFR. Since the interference of multiple elbows should be investigated to understand turbulent flow in the cold-leg pipe geometry, 1 /15-scale experiments with double elbows were carried out to clarify that flow in the first elbow influenced a flow separation behavior in the second elbow. Simulation activities include Unsteady Reynolds Averaged Navier Stokes equation (U-RANS) approach with a Reynolds stress model using a commercial computational fluid dynamics (CFD) code and Large Eddy Simulation (LES) approach using an in-house code. A hybrid approach that combined with RANS and LES was also applied using a CFD code. Several numerical results appear in this paper, focusing on its applicability to the hot-leg pipe experiments. These simulations reasonably agreed with the experimental data using the 1/3-scale test section.

DOI： 10.1080/18811248.2011.9711749

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Japan Society of Mechanical Engineers  

LDV measurements in a 90 degrees elbow were examined for the cases of inflow from a long pipe, short pipe and swirl generator. The elbow is considered as a 1/10 scale hot-leg piping model of a Japanese sodium-cooled fast breeder reactor (JSFR). Time-averaged flow distribution for the Reynolds number of 320000, based on the inner pipe diameter and bulk velocity, shows that shortening the upstream pipe length to 4.9D from 10D induces the flow separation downstream of the elbow. Detailed observation shows that shortening upstream pipe weakens the Prandtl's secondary flow of the first kind. This suppresses the kinetic energy transport from the outer to inner side of the elbow. Swirl generator in the present experimental setting generates the swirling inflow with the non-dimensional angular momentum of 0.12, based on the inner pipe diameter and bulk velocity. The circumferential velocity distribution formed a shape like Rankin's combined vortex in the elbow inlet, and the accelerated axial velocity at the vortex center is observed. The axial velocity distribution however is found to be almost the same as that of the non-swirl inflow case in the latter half of the elbow. Frequency analyses shows that the Strouhal number by vortex shedding from the boundary layer occurring at the inner side became 0.5, except for 0.6 in the case of the long pipe case. This might be related with the boundary layer width and the local flow velocity.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Nanofiber aggregation were observed under simple shear, which was generated by rheometer. The rheometer used has parallel plates and cone-and-plates geometries. The Nanofiber (bacteria cellulose fiber) having 50 nm in diameter was extracted from nata de coco and suspended uniformly at 0.5 wt% concentration to glycerin. The torque, which was measured by rheometer, continued to increase with time and did not stay at constant value during 10 minutes of measurement. This is because the nanofibers were formed into wormlike aggregation and it enlarged with time. The diameter of the wormlike aggregation became 1.4 times greater than the length between parallel plates at the end of measurement.

DOI： 10.1299/jsmemecjo.2010.2.0_39

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

Pressure measurements, laser Doppler velocimetry (LDV) and flow visualization were carried out for a 90° elbow with a curvature that coincides with the pipe inside diameter in order to clalify the structure of a fluid fluctuation occuring in the bend. Results of pressure measurements show that the value of the pressure loss occurring in the elbow coincides with the conventional empirical formula with a turbulent boundary layer. This agreement is applicable to the case that Reynolds number is greater than 50 000. Detailed results of LDV measurement for Reynolds number of 50 000 is shown. Frequency analyses of axial velocities indicate that two kinds of flow fluctuations exist in the present elbow. One is the fluctuation with approximate Strohal number (based on a pipe inner diameter and a bulk velocity) of 1.0 occurring in a shear flow region. The other is with approximate Strouhal number of 0.5 occurring in the separated and its downstream regions. These fluctuations were also observed by flow visualization.

DOI： 10.1299/kikaib.76.765_830

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Secondary vortex enhancement was examined for fiber suspension flows containing bacteria cellulose fiber (BCF) at weight fractions from 0.07 to 0.28 wt%. BCFs were derived from nata de coco. These fluids have non-Newtonian properties even at low weight fraction of BCF. The channel used has a rectangular cross section and an abrupt contraction geometry. As a result, we found that the vortex becomes large as increasing flow rate for BCF suspensions, whereas it becomes small for a Newtonian fluid. The vortex size enhancement is probably caused by the increment of elongational viscosity of test fluid.

DOI： 10.1299/jsmemecjo.2009.2.0_85

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

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Flow characteristics of surfactant solution flowing in a curved circular pipe were investigated experimentally by means of pressure measurement and laser doppler anemometry. The curvature radius of the present pipe is twice as the same as its diameter (2×85.1mm), and Reynolds number and the concentration of the solution investigated in LDV measurement were 60000 and 100ppm, respectively. It was found that the region that has larger velocity deviated inner at the inlet of the curved part, and outer at the exit, compared with the water. It was also found that the secondary flow became stronger, and flow mixing between large and small velocities did not occur much till the velocity shear rate reaches to its of shear-thinning.

DOI： 10.1299/jsmemecjo.2007.2.0_9

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Reynolds shear stress of surfactant solution flowing in a circular pipe was investigated experimentally by means of Laser Doppler anemometery. Concentrations of surfactant solution were 0, 28, 50, 100 ppm, and Reynolds numbers based on a bulk velocity, viscosity of water and a pipe diameter were set to 20000, 40000, 60000. Results show that the extreme suppression of Reynolds shear stress compared to water was occurred in the case of surfactant solution, and this was achieved by counteractions between outward interaction and ejection, inward interaction and sweep, respectively. The shear viscosity calculated from mean velocity distribution and previous results of rheometer test shows that there is a low viscosity region below the region which is in a shear induced state. This region makes a difference in streamwise velocity fluctuation between the cases of upward and downward fluid motion.

DOI： 10.1299/jsmemecjo.2006.2.0_63

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

Effects of ultrasonic vibrations on a turbulent (Re=7000±50) square-duct flow were investigated experimentally by means of LDV (Laser Doppler Velocimetry). Ultrasound was introduced into the flow by PZT-type transducers attached to the trapezoidal horn. The height range of the horn tip was in between the buffer layer and the fully turbulent region. Driven frequency and power supplied to transducers were nominally 45.5kHz and 20W respectively. The result shows that ultrasound makes low speed region near the center of the duct bottom wall, and that it entrains the flow in the center region to the horn. In the present horn arrangement shown in Fig. 2, the counter-clockwise (viewing from the upstream) vortex may lie in the lower left quarter square of the duct cross section. This is mainly caused by acoustic streaming. The test varying ultrasound frequency and power shows that it is clarified that main feature in the present study is caused by acoustic streaming, not the vibration transmitted from the horn itself.

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

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Japan Society of Mechanical Engineers  

Developing pipe flow of surfactant solutions is investigated experimentally at surfactant concentrations below 100ppm. The rheological behavior of the surfactant solution is clarified based on measurements of the relationship between shear stress and shear rate, and the velocity distribution is investigated based on laser Doppler velocimetry measurements. The results indicate that a maximum drag reduction effect of 70% can be achieved by the addition of surfactant to water, and close to laminar flow can be achieved under drag-suppressed conditions. The velocity distribution under drag-suppressed flow is shown to approach that given by Virk's equation.

DOI： 10.1299/jsmemecjo.2005.2.0_157

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

Recently in nuclear plants, it has occurred thermal fatigue failure accidents because of thermal fluctuations that called Thermal Striping in T-junction where mixed a higher temperature sodium and a colder temperature sodium into each other. Then, we set up turbulence promoter in T-junction piping system, effects of turbulence promoter on flow characteristics have been investigated experimentally using flow visualization techniques (the dye injection method) and velocity measurement by LDV. As a result, it is clarified that secondary streams in pipe sections becomes stronger and diffusion of momentum is promoted in case with turbulent promoter.

DOI： 10.3154/jvs.24.Supplement2_135

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Visualization by the dye injection method and velocity measurements are carried out in a T-junction piping system with turbulent promoter under the isothermal condition, and the behavior of main and branch pipe flow is examined experimentally. As a result, it is clarified that secondary streams in pipe sections becomes stronger and diffusion of momentum is promoted in case with turbulent promoter.

DOI： 10.1299/jsmemecjo.2004.2.0_335

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本ガスタービン学会  

In the first report, the results of numerical studies for viscous flow passing through a two-dimensional supersonic cascade are reported. There, the flow instability called as forward traveling fluctuation with oscillating passage shock was shown. The present study reports the results of inviscid flow calculations in order to clarify the contribution of viscosity to this type of the flow instability. Results show that this type can occur also in inviscid flow. In reference (2)〜(9), shock fluctuation is explained as the interaction of the boundary layer/trailing vortex fluctuation. This type found in the first report may be another type of flow instability since it can be predicted also in inviscid calculations.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：公益社団法人日本ガスタービン学会  

Numerical studies were carried out to investigate instabilities of viscous and supersonic flow in a two-dimensional cascade. Unsteady phenomena with circumferentially traveling fluctuation were found near the peak back pressure points. They are grouped into four types : (1) conventional rotating stall, (2) backward traveling fluctuation related with fluctuating leading edge shock, (3) intermittently appearing, forward and backward traveling fluctuation, and (4) forward traveling fluctuation with oscillating passage shock. Rotating stall was observed only for subsonic inlet. The second and third types are related with an interaction between expansion waves emanated from the blade suction surfaces and leading edge/detached shocks. The forth type is caused by an interaction between the downstream higher pressure region and the passage shock. It was found the rotating stall and forward traveling fluctuation correspond to those predicted by an actuator disk analysis.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper presents the results of a two-dimensional stability analysis on supersonic flows using actuator disk methods. The relative flow is supersonic with subsonic axial component. The purpose of this study is to clarify the characteristics of the flow fluctuation which propagates slower than the cascade rotation. This flow fluctuation was found in CFD by Iwamoto, which suggested that this flow fluctuation is related with a detached shock oscillation and unstarted leak flow. The present actuator disk model involves these effects. The solution shows the possibility of the existence of the destabilizing mode in the supersonic cascade. The propagation velocity predicted by the present method agrees with that found in CFD.

DOI： 10.1299/jsmemecjo.2000.4.0_61

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This paper presents the results of a two-dimensional stability analysis on supersonic flow relative to a cascade, using actuator disk methods. The results show the possibility of existence of two types of destabilizing mode in the supersonic cascade flow. One mode corresponds to conventional rotating stall in subsonic cascade flows. This mode can be unstable both in subsonic and supersonic regions, and its propagation velocity ratio (absolute propagation velocity/rotor speed) is smaller than unity. The other mode is a newly found mode unique to supersonic cascade flows. This mode can become unstable only in the supersonic region, and its propagation velocity ratio is for the most cases larger than unity. Both modes become unstable due to the positive slope of the characteristic curves caused by flow compressibility as in the case of, for example, a shock wave.

DOI： 10.1299/jsmeb.41.530

Web of Science

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

Web of Science

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人日本機械学会  

This paper presents the results of a two-dimensional stability analysis on supersonic flow relative to a cascade, using actuator disk methods. The results show the possibility of existence of two types of destabilizing mode in the supersonic cascade flow. One mode corresponds to conventional rotating stall in subsonic cascade flows. This mode can be unstable both in subsonic and supersonic regions, and its propagation velocity ratio is smaller than unity. The other mode is a newly found mode unique to supersonic cascade flows. This mode can become unstable only in the supersonic region, and its propagation velocity ratio is in most cases larger than unity. Both modes become unstable due to the positive slope of the characteristic curves produced by flow compressibility as in the case of, for example, a shock wave.

DOI： 10.1299/kikaib.63.2667

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)   Publisher：大阪大学サイバーメディアセンター  

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Language：English   Publishing type：Research paper, summary (international conference)  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This report shows the fluid property and the velocity profile of carbon nanotube suspension (CNT). The CNT suspension is complex fluid. Complex fluid is defined as any fluid that does not follow the well-known Newton's law. In this study, two-dimensional velocity profiles of CNT suspension were measured between parallel plates and at the upstream region of the contraction. These results show that the velocity profiles in CNT suspension between parallel plates were in good agreement with Newtonian one. However, the results in CNT suspension at the upstream region of the contraction were not agreement with Newtonian one. This is because the elongational viscosities of CNT suspension effect at the upstream of the contraction.

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Language：English   Publisher：The Japan Society of Mechanical Engineers  

Wall pressure measurements were conducted for a 90 degree elbow of which the axis curvature coincided with its inner diameter (125 mm). Reynolds numbers examined were 3.2 X 105 and 5.0 X 105. Results showed that distributions of fluctuating normalized pressures obtained here and those made by Shiraishi et al. for the Reynolds number of 3.25 X 106 [1] coincided within 0.02 of the dynamic pressure. Power spectral density functions of fluctuating pressures mostly exhibited the slope of the minus seven-third law at large frequencies. The peak spectrum with the Strouhal number of 0.5 could be found in the curvature inside downstream of the elbow. They corresponded to the vortex shedding from the boundary layer developed in the inner and aft part of the elbow. The peak intensity having the Strouhal number of 0.5 quantitatively was in accordance with that of the data obtained in the experimental setup that Shiraishi et al. used [2], suggesting that the law of dynamical similarity could be applied with regard to this oscillation.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In the present study, we report and discuss that an apparent slip on a wall of a microchannel has been observed with polymer solution flow. The aqueous solutions of polymer, which are non-Newtonian fluids, used in our experiments are anionic and nonionic ones, respectively. An aqueous solution of glycerin, which is Newtonian fluid, is also used for comparison. The wall of microchannel is made of two types of glass: normal glass and ITO(indium tin oxide)-coated glass. The ITO-coated glass is also transparent. The flow channel is constructed by having a glass plate and PDMS chip (silicone rubber) bonded. In the experiment of anionic polymer solution, the apparent slip was observed on the wall of normal glass, but not with the one of ITO-coated glass. For the nonionic polymer solution, the apparent slip was observed both on the normal and ITO-coated glasses. These phenomena are caused by the interaction between the polymer and the wall.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Flow structures of a polymer solution in a planer channel with a 4:1 abrupt contraction have investigated utilizing an optical rheometric device which is combined with a microscope. Distributions of flow-induced birefringence and velocity field were measured with Xanthan gum solution. The measurement of the birefringence was conducted in every 100μm step along the width direction of the channel. The birefringence measured around the centerline of channel became larger in the converging flow generated in the upstream region of the abrupt contraction. Moreover, in this region, average orientation of the polymer molecules were agree with the flow direction defined with velocity vectors. It is considered that contribution of the elongational flow and the shear flow generated in this region of the planer channel to stretch the polymer molecules has same direction.

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Language：Japanese   Publishing type：Meeting report   Publisher：日本混相流学会  

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LDV measurements in a 90 degrees elbow which curvature radius coincides with the diameter have been examined for the case of a deflected inflow that became faster at the inside. Comparison with a result of an inflow from a short pipe that measures 4.9D shows that the deflected inflow reinforced a convex velocity distribution occurring near the curvature inside in the downstream region. This result concludes that the deflected inflow promotes the secondary flow of Prandtl's first kind in the elbow. Frequency analyses of axial flow fluctuations show that the dominant frequency can be seen in the downstream of the elbow even in the deflected inflow case. However its Strouhal number increases to 0.6 from 0.5, compared with the short pipe case. Results of frequency analyses are also shown for other cases, i.e. an inflow from a long pipe (having an axial length of 10D) and a swirl generator. Dominant Strouhal numbers in most of the cases become 0.5, except for 0.6 in cases of the inflow from the long pipe and deflector. This frequency shift might be related with the boundary layer size and the local flow velocity, since the corresponding fluctuation is caused by vortex shedding from the boundary layer at the elbow inside.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In Japan Atomic Energy Agency (JAEA), a study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius ("short-elbow") has been conducted. Flow-induced vibration in the short-elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this paper, unsteady flow characteristics in the JSFR short-elbow pipe related to the large-scale eddy motion were estimated based on knowledge from existing studies for curved pipes and scaled water experiments and numerical simulations for the JSFR hot-leg piping.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In Japan Atomic Energy Agency (JAEA), a study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius has been conducted. Flow-induced vibration in the elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this study, applicability of the Unsteady Reynolds Averaged Navie-Stokes equations (U-RANS) approach with the Reynolds Stress Model (RSM) using a commercial CFD code to the flow through the short-elbow under high Reynolds number condition was examined for the 1/10 scaled water experiment simulating the hot-leg piping of the JSFR. As a result, the time-step dependency is observed in flow structure.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)   Publisher：日本原子力研究開発機構  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：Japan Society of Mechanical Engineers  

Pressure measurements, laser Doppler velocimetry (LDV) and flow visualization were carried out for a 90° elbow with a curvature that coincides with the pipe inside diameter in order to clalify the structure of a fluid fluctuation occuring in the bend. Results of pressure measurements show that the value of the pressure loss occurring in the elbow coincides with the conventional empirical formula with a turbulent boundary layer. This agreement is applicable to the case that Reynolds number is greater than 50 000. Detailed results of LDV measurement for Reynolds number of 50 000 is shown. Frequency analyses of axial velocities indicate that two kinds of flow fluctuations exist in the present elbow. One is the fluctuation with approximate Strohal number (based on a pipe inner diameter and a bulk velocity) of 1.0 occurring in a shear flow region. The other is with approximate Strouhal number of 0.5 occurring in the separated and its downstream regions. These fluctuations were also observed by flow visualization.

DOI： 10.1299/kikaib.76.765_830

Scopus

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publishing type：Rapid communication, short report, research note, etc. (bulletin of university, research institution)   Publisher：愛媛大学  

Recently, in T-junction piping systems of plants, fluid temperature fluctuations due to mixing of hot and cold fluids induces thermal fatigue of structure. This phenomenon is called thermal striping and its study is significant in term of the safety and design of a fast reactor. In this study, in order to reduce fluid temperature fluctuations, the turbulence promoter is installed and the flows downstream of T-junction are investigated experimentally. From the experimental results, effects of turbulence promoter on flow characteristics are examined. It is clarified that secondary streams in pipe cross sections becomes stronger and diffusion of momentum is promoted.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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Language：English   Publishing type：Rapid communication, short report, research note, etc. (scientific journal)  

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The effect of ultrasonic vibration in the Reynolds number (Re) ranger of 1500 to 7000 on fluid flow in a square channel was investigated experimentally as basic research of control of turbulence flow. By applying ultrasonic vibration to the laminar flow, the transition to turbulent flow from laminar flow was promoted downstream. When a trapezoidal horn transducer was fixed at the side wall of a channel, acoustic streaming from the horn tip was induced by this transducer, and spanwise velocity in the channel increases by this streaming. In turbulent regions, turbulence can be restrained by the ultrasonic vibration near the wall. Acoustic cavitation near the wall causes a reduction of turbulence intensity in turbulent regions.

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Language：Japanese   Publisher：京都大学  

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Other Link： http://hdl.handle.net/2433/42439

Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Numerical analyses were carried out to understand the unsteady characteristics of unstarted flow near the stall line in a two-dimensional supersonic cascade. The result shows that detached shock on the blade suction side moves upstream to the blade leading edge of the preceding blade as we increase the pressure ratio. The accelerated region upstream of the shock becomes smaller as the shock moves upstream. The shock disappears when it reaches the leading edge on the suction side because the flow upstream of the shock is not sufficiently accelerated. The disappeared shock will not recover because leading edge suction is weakened by separation which was behind the shock. These phenomena are considered to be the inception of full stall in unstarted flow.

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Language：English   Publisher：Gas Turbine Society of Japan  

Two-dimensional unsteady flows which have a supersonic inlet with a subsonic axial component relative to the cascade were calculated numerically. The ARL-SL19 cascade (Tweedt et al., 1988) data was used for the cascade geometry. Calculations are made assuming a periodicity over 10 blades for the two cases of the blade Mach number, v_1/c_<01abs>=1.3 and 1.5 to examine the shock related instabilities predicted by our linear stability analysis based on an actuator disk method (Iwamoto et al., 1998). For v_1/c_<01abs>=1.5, it was found that the flow fluctuation propagates in the direction opposite to the cascade rotation with a relative velocity 19% of the rotor speed near the stall line. This fluctuation is caused by the moving higher Mach number region in the upstream which is emanating from the suction side near the leading edge. For v_1/c_<01abs>=1.3, no propagating fluctuations were observed near the stall line. However, when the back pressure is 2% less than the near-stall point, it was found that the flow fluctuation propagates in the same direction as the cascade rotation with a relative velocity 119% of the rotor speed. This type of fluctuation was not observed in the case of v_1/c_<01abs>=1.5, and is driven by the interaction between the higher pressure in the cascade discharge area and the passage shock. In the last section, the comparison of propagating velocities of the numerical result and of our previous linear analysis is presented. The propagating velocity of the forward travelling fluctuation in the numerical result agrees well with the linear analysis solution which is considered to be an instability associated with a shock.

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Language：Japanese   Publisher：公益社団法人日本ガスタービン学会  

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Event date： 2023.3

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Event date： 2022.9

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Event date： 2021.9

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Event date： 2020.9

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Effects of ultrasonic vibrations on turbulent (Re=7000±50) square-duct flow were investigated experimentally by means of LDV. Ultrasound was introduced into the flow by Langevin PZT-type transducers attached to the trapezoidal horn. Three cases of horn arrangements were investigated: the horn is located at the sidewall near the bottom, at the corner between sidewall and bottom, and at the center of the sidewall. Driven frequency and power supplied to transducers were 45±2 kHz and mainly 20 W respectively. Results show that acoustic streaming varies the distribution of Reynolds shear stress, and its change is explained by conventional momentum transfer theory. The experiment varying ultrasonic power shows that the region of ultrasonic vibration can be adjusted in case that the horn is located at the sidewall near the bottom, since this case is less affected by inertia of main flow compared with other cases.

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Reynolds shear stress of surfactant solution flowing in a circular pipe was investigated experimentally by means of Laser Doppler anemometery. Concentrations of surfactant solution were 0, 28, 50, 100 ppm, and Reynolds numbers based on a bulk velocity, viscosity of water and a pipe diameter were set to 20000, 40000, 60000. Results show that the extreme suppression of Reynolds shear stress compared to water was occurred in the case of surfactant solution, and this was achieved by counteractions between outward interaction and ejection, inward interaction and sweep, respectively. The shear viscosity calculated from mean velocity distribution and previous results of rheometer test shows that there is a low viscosity region below the region which is in a shear induced state. This region makes a difference in streamwise velocity fluctuation between the cases of upward and downward fluid motion.

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Flow characteristics of surfactant solution flowing in a curved circular pipe were investigated experimentally by means of pressure measurement and laser doppler anemometry. The curvature radius of the present pipe is twice as the same as its diameter (2×85.1mm), and Reynolds number and the concentration of the solution investigated in LDV measurement were 60000 and 100ppm, respectively. It was found that the region that has larger velocity deviated inner at the inlet of the curved part, and outer at the exit, compared with the water. It was also found that the secondary flow became stronger, and flow mixing between large and small velocities did not occur much till the velocity shear rate reaches to its of shear-thinning.

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Secondary vortex enhancement was examined for fiber suspension flows containing bacteria cellulose fiber (BCF) at weight fractions from 0.07 to 0.28 wt%. BCFs were derived from nata de coco. These fluids have non-Newtonian properties even at low weight fraction of BCF. The channel used has a rectangular cross section and an abrupt contraction geometry. As a result, we found that the vortex becomes large as increasing flow rate for BCF suspensions, whereas it becomes small for a Newtonian fluid. The vortex size enhancement is probably caused by the increment of elongational viscosity of test fluid.

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In Japan Atomic Energy Agency (JAEA), a study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius has been conducted. Flow-induced vibration in the elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this study, applicability of the Unsteady Reynolds Averaged Navie-Stokes equations (U-RANS) approach with the Reynolds Stress Model (RSM) using a commercial CFD code to the flow through the short-elbow under high Reynolds number condition was examined for the 1/10 scaled water experiment simulating the hot-leg piping of the JSFR. As a result, the time-step dependency is observed in flow structure.

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Nanofiber aggregation were observed under simple shear, which was generated by rheometer. The rheometer used has parallel plates and cone-and-plates geometries. The Nanofiber (bacteria cellulose fiber) having 50 nm in diameter was extracted from nata de coco and suspended uniformly at 0.5 wt% concentration to glycerin. The torque, which was measured by rheometer, continued to increase with time and did not stay at constant value during 10 minutes of measurement. This is because the nanofibers were formed into wormlike aggregation and it enlarged with time. The diameter of the wormlike aggregation became 1.4 times greater than the length between parallel plates at the end of measurement.

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LDV measurements in a 90 degrees elbow which curvature radius coincides with the diameter have been examined for the case of a deflected inflow that became faster at the inside. Comparison with a result of an inflow from a short pipe that measures 4.9D shows that the deflected inflow reinforced a convex velocity distribution occurring near the curvature inside in the downstream region. This result concludes that the deflected inflow promotes the secondary flow of Prandtl's first kind in the elbow. Frequency analyses of axial flow fluctuations show that the dominant frequency can be seen in the downstream of the elbow even in the deflected inflow case. However its Strouhal number increases to 0.6 from 0.5, compared with the short pipe case. Results of frequency analyses are also shown for other cases, i.e. an inflow from a long pipe (having an axial length of 10D) and a swirl generator. Dominant Strouhal numbers in most of the cases become 0.5, except for 0.6 in cases of the inflow from the long pipe and deflector. This frequency shift might be related with the boundary layer size and the local flow velocity, since the corresponding fluctuation is caused by vortex shedding from the boundary layer at the elbow inside.

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In Japan Atomic Energy Agency (JAEA), a study on flow induced vibration in the primary cooling system of Japan Sodium cooled Fast Reactor (JSFR) consisting of large diameter pipe and pipe elbow with short curvature radius ("short-elbow") has been conducted. Flow-induced vibration in the short-elbow is an important issue in design study of JSFR, because it may affect to structural integrity of the pipe. In this paper, unsteady flow characteristics in the JSFR short-elbow pipe related to the large-scale eddy motion were estimated based on knowledge from existing studies for curved pipes and scaled water experiments and numerical simulations for the JSFR hot-leg piping.

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This report shows the fluid property and the velocity profile of carbon nanotube suspension (CNT). The CNT suspension is complex fluid. Complex fluid is defined as any fluid that does not follow the well-known Newton's law. In this study, two-dimensional velocity profiles of CNT suspension were measured between parallel plates and at the upstream region of the contraction. These results show that the velocity profiles in CNT suspension between parallel plates were in good agreement with Newtonian one. However, the results in CNT suspension at the upstream region of the contraction were not agreement with Newtonian one. This is because the elongational viscosities of CNT suspension effect at the upstream of the contraction.

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Language：Japanese   Presentation type：Oral presentation (general)  

In the present study, we report and discuss that an apparent slip on a wall of a microchannel has been observed with polymer solution flow. The aqueous solutions of polymer, which are non-Newtonian fluids, used in our experiments are anionic and nonionic ones, respectively. An aqueous solution of glycerin, which is Newtonian fluid, is also used for comparison. The wall of microchannel is made of two types of glass: normal glass and ITO(indium tin oxide)-coated glass. The ITO-coated glass is also transparent. The flow channel is constructed by having a glass plate and PDMS chip (silicone rubber) bonded. In the experiment of anionic polymer solution, the apparent slip was observed on the wall of normal glass, but not with the one of ITO-coated glass. For the nonionic polymer solution, the apparent slip was observed both on the normal and ITO-coated glasses. These phenomena are caused by the interaction between the polymer and the wall.

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Language：Japanese   Presentation type：Oral presentation (general)  

Flow structures of a polymer solution in a planer channel with a 4:1 abrupt contraction have investigated utilizing an optical rheometric device which is combined with a microscope. Distributions of flow-induced birefringence and velocity field were measured with Xanthan gum solution. The measurement of the birefringence was conducted in every 100μm step along the width direction of the channel. The birefringence measured around the centerline of channel became larger in the converging flow generated in the upstream region of the abrupt contraction. Moreover, in this region, average orientation of the polymer molecules were agree with the flow direction defined with velocity vectors. It is considered that contribution of the elongational flow and the shear flow generated in this region of the planer channel to stretch the polymer molecules has same direction.

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese   Presentation type：Oral presentation (general)  

researchmap

Language：Japanese  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：English   Presentation type：Oral presentation (general)  

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese   Presentation type：Oral presentation (general)  

This paper presents the results of a two-dimensional stability analysis on supersonic flows using actuator disk methods. The relative flow is supersonic with subsonic axial component. The purpose of this study is to clarify the characteristics of the flow fluctuation which propagates slower than the cascade rotation. This flow fluctuation was found in CFD by Iwamoto, which suggested that this flow fluctuation is related with a detached shock oscillation and unstarted leak flow. The present actuator disk model involves these effects. The solution shows the possibility of the existence of the destabilizing mode in the supersonic cascade. The propagation velocity predicted by the present method agrees with that found in CFD.

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Numerical analyses were carried out to understand the unsteady characteristics of unstarted flow near the stall line in a two-dimensional supersonic cascade. The result shows that detached shock on the blade suction side moves upstream to the blade leading edge of the preceding blade as we increase the pressure ratio. The accelerated region upstream of the shock becomes smaller as the shock moves upstream. The shock disappears when it reaches the leading edge on the suction side because the flow upstream of the shock is not sufficiently accelerated. The disappeared shock will not recover because leading edge suction is weakened by separation which was behind the shock. These phenomena are considered to be the inception of full stall in unstarted flow.

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

The effect of ultrasonic vibration in the Reynolds number (Re) ranger of 1500 to 7000 on fluid flow in a square channel was investigated experimentally as basic research of control of turbulence flow. By applying ultrasonic vibration to the laminar flow, the transition to turbulent flow from laminar flow was promoted downstream. When a trapezoidal horn transducer was fixed at the side wall of a channel, acoustic streaming from the horn tip was induced by this transducer, and spanwise velocity in the channel increases by this streaming. In turbulent regions, turbulence can be restrained by the ultrasonic vibration near the wall. Acoustic cavitation near the wall causes a reduction of turbulence intensity in turbulent regions.

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese  

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Language：Japanese   Presentation type：Oral presentation (general)  

Visualization by the dye injection method and velocity measurements are carried out in a T-junction piping system with turbulent promoter under the isothermal condition, and the behavior of main and branch pipe flow is examined experimentally. As a result, it is clarified that secondary streams in pipe sections becomes stronger and diffusion of momentum is promoted in case with turbulent promoter.

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Language：Japanese   Presentation type：Oral presentation (general)  

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Language：Japanese  

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Language：Japanese  

Developing pipe flow of surfactant solutions is investigated experimentally at surfactant concentrations below 100ppm. The rheological behavior of the surfactant solution is clarified based on measurements of the relationship between shear stress and shear rate, and the velocity distribution is investigated based on laser Doppler velocimetry measurements. The results indicate that a maximum drag reduction effect of 70% can be achieved by the addition of surfactant to water, and close to laminar flow can be achieved under drag-suppressed conditions. The velocity distribution under drag-suppressed flow is shown to approach that given by Virk's equation.

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Language：Japanese  

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