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Experimental Study of the Flow in Helical Circular Pipes:Torsion Effect on the Flow Velocity and Turbulence

Journal of Thermal Science 2008年第3期17卷 193-198页

作者： Yasutaka HAYAMIZU kyoji yamamoto ShinichiroYANASE Toru HYAKUTAKE Toru SHINOHARA Shinichi MORITA Department of Mechanical Engineering Yonago National College of Technology Graduate School of Natural Science and Technology Okayama University

An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β0, which is defined by β0 = τ/（2δ）1/2 with non-dimensional torsion r, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows： The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion （toroidal pipe） to a single vortex type after one of the twin-vortex gradually disappears as β0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β0, but changes its shape as β0 increases, and attains the shape similar to that in a straight circular pipe when ,β0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as ,β0 increases for small ,β0, and then increases after taking a minimum at ,β0 ≈ 1.4 as ,β0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at ,β0 ≈ 1.4.

关键词： Helical Circular Pipe Torsion Effect Critical Reynolds Number Turbulence

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Experimental Study of the Viscous Pump with a Helical Channel Rotor:Torsion Effect of the Channel

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Journal of Thermal Science 2010年第2期19卷 154-159页

作者： Yasutaka HAYAMIZU kyoji yamamoto Shinichiro YANASE Toru HYAKUTAKE Shinichi MORITA Shigeru OHTSUKA Department of Mechanical Engineering Yonago National College of Technology4448 Hikona-choYonago-shiTottori 683-8502 Graduate School of Natural Science and Technology Okayama University3-1-1 TushimanakaOkayama-shiOkayama 700-8530

The viscous pump,which has a rotor with a helical square channel,is studied *** non-dimen-sional channel curvature is taken to be about *** types of torsion of the channel are made to investigate the torsion effect on the flow *** measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the *** also observe the secondary flow at a cross-section of the *** of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is *** for the secondary flow in a cross-section,there appear several types of *** there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is *** secondary flow becomes asymmetric as the rotation is *** have unsteady flow patterns at large flux and rotation.

关键词： Viscous Pump Helical Channel Torsion Effect Secondary Flow Flow Visualization Dean Number Taylor Number

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A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing

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Open Journal of Fluid Dynamics 2014年第5期4卷 463-471页

作者： Toshihiko Kawabe Yasutaka Hayamizu Shinichiro Yanase Takeshi Gonda Shinichi Morita Shigeru Ohtsuka kyoji yamamoto Technical Division Tsurumi Manufacturing Co. Ltd. Tottori Japan Department of Mechanical Engineering Yonago National College of Technology Tottori Japan Graduate School of Natural Science and Technology Okayama University Okayama Japan

Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.

关键词： Taylor-Dean Flow Chaotic Mixing Secondary Flow LIF CFD

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A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow

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Open Journal of Fluid Dynamics 2012年第4期2卷 195-201页

作者： Yasutaka Hayamizu Shinichiro Yanase Shinichi Morita Shigeru Ohtsuka Takeshi Gonda Kazunori Nishida kyoji yamamoto Department of Mechanical Engineering Yonago National College of Technology Tottori Japan Graduate School of Natural Science and Technology Okayama University Okayama Japan

The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ1/2, the Reynolds number Re=qdh/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)1/2Ωa2/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.

关键词： Chaos Rotation Effect Secondary Flow PIV LIF

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A Micromixer Using the Taylor-Dean Flow: Effects of Aspect Ratio and Inflow Condition on the Mixing

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Open Journal of Fluid Dynamics 2015年第3期5卷 256-264页

作者： Yasutaka Hayamizu Toshihiko Kawabe Shinichiro Yanase Takeshi Gonda Shinichi Morita Shigeru Ohtsuka kyoji yamamoto Department of Mechanical Engineering Yonago National College of Technology Tottori Japan Technical Division Tsurumi Manufacturing Co. Ltd. Tottori Japan Graduate School of Natural Science and Technology Okayama University Okayama Japan

Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.

关键词： Component Taylor-Dean Flow Chaotic Mixing Secondary Flow LIF CFD

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Multi-Physics CFD Simulations in Engineering

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Journal of Thermal Science 2013年第4期22卷 287-293页

作者： Makoto yamamoto Tokyo University of Science Department of Mechanical Engineering 6-3-1 NiijukuKatsushika-ku Tokyo 125-8585 Japan

Nowadays Computational Fluid Dynamics （CFD） software is adopted as a design and analysis tool in a great number of engineering fields. We can say that single-physics CFD has been suffciently matured in the practical point of view. The main target of existing CFD software is single-phase flows such as water and air. However, many multi-physics problems exist in engineering. Most of them consist of flow and other physics, and the interactions between different physics are very important. Obviously, multi-physics phenomena are critical in devel- oping machines and processes. A multi-physics phenomenon seems to be very complex, and it is so difficult to be predicted by adding other physics to flow phenomenon. Therefore, multi-physics CFD techniques are still under research and development. This would be caused from the facts that processing speed of current computers is not fast enough for conducting a multi-physics simulation, and furthermore physical models except for flow physics have not been suitably established. Therefore, in near future, we have to develop various physical models and ef- ficient CFD techniques, in order to success multi-physics simulations in engineering. In the present paper, I will describe the present states of multi-physics CFD simulations, and then show some numerical results such as ice accretion and electro-chemical machining process of a three-dimensional compressor blade which were obtained in my laboratory. Multi-physics CFD simulations would be a key technology in near future.

关键词： Computational fluid dynamics Multi-physics Engineering problems

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SYNTHESIS AND CHARACTERIZATION OF SOLUBLE POLYPHENYLENE COMPOSED OF p-PHENYLENE AND m-PHENYLENE UNITS

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Chinese Journal of Polymer Science 2002年第4期20卷 333-337页

作者： Takakazu yamamoto Chemical Resources Laboratory Tokyo Institute of Technology Tokyo Japan

NiCl2(bpy) catalyzed polycondensation between p-dibromobenzene and m-dibromobenzene has been carried out under various conditions. The polycondensation endows the copolymer with an M-n of 2300 (by GPC, polystyrene standards) and good solubility in organic solvents. The fluorescence spectra of the copolymer measured with tetrahydrofuran solution shows an emission maximum (lambda(max)) at 372.8 nm, whereas for the film the maximum shifts to 436.6 nm.

关键词： polyphenylene copolycondensation conjugated polymer

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Flow separation control by using bowed blade in highly loaded turbine cascades

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Science China(Technological Sciences) 2009年第6期52卷 1471-1477页

作者： yamamoto Atsumasa Japan Aerospace Exploration Agency

Due to the serious flow separations and centralized vortices,there are high secondary losses in highly loaded *** is imperative to find measures to control the flow separation and vortices hence improve the turbine *** paper reports our recent progress on flow separation and vor-tices control in highly loaded turbine cascades by using bowed *** sets of highly loaded tur-bine cascades with the turning angles of 113° and 160°,and each with 7 bowed blade angles 0°(straight),±10°,±20° and ±30° were experimentally *** internal flow field measurement and flow visualization on the blade surfaces were conducted,and the effects of blade bowing on the flow topology,distribution of vorticity and the flow energy loss were *** results show that,for the cascade with the turning angle of 113°,the appropriately positive bow angle could reduce the flow energy loss;whereas for the cascade with the turning angle of 160°,the well selected negative bow angle can give the better aerodynamic performance.

关键词： turbine cascade turning angle flow separation bowed blade

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Prevention of recurrence after surgery for Crohn's disease: Efficacy of infliximab

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World Journal of Gastroenterology 2010年第43期16卷 5405-5410页

作者： Takayuki yamamoto Inflammatory Bowel Disease Center and Department of Surgery Yokkaichi Social Insurance Hospital

After surgery for Crohn's disease (CD), early endoscopic lesions are frequently observed despite no symptomatic recurrence. The severity of lesions found at postoperative endoscopy is reported to be a strong predictive factor for future clinical recurrence. If endoscopic lesions in the early postoperative period can be reduced with medications, symptomatic recurrence will likely be delayed and decreased. Before the introduction of biologic therapies, various medications were used for the maintenance of clinical remission after surgery; however, few demonstrated consistent efficacy. Infliximab is a recombinant anti-tumor necrosis factor-α antibody. Although infliximab is one of the most effective medications in the management of CD, its efficacy for early endoscopic lesions after surgery has not yet been assessed. The author and colleagues recently conducted a prospective study in order to investigate the impact of infliximab on early endoscopic lesions after resection for CD. We found that infliximab therapy showed clear suppressive effects on clinical and endoscopic disease activity in patients with early endoscopic lesions after resection.

关键词： Crohn’s disease Postoperative recurrence Endoscopic lesion Infliximab

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An Inverse Problem for Maxwell's Equations in Anisotropic Media

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Chinese Annals of Mathematics,Series B 2007年第1期28卷 35-54页

作者： Masahiro yamamoto Graduate School of Mathematical Sciences The University of Tokyo 3-8-1 Komaba Meguro Tokyo 153Japan

The authors consider Maxwell＇s equations for an isomagnetic anisotropic and inhomogeneous medium in two dimensions, and discuss an inverse problem of determining the permittivity tensor （ε1,ε2,ε2,ε3 ） and the permeability μ in the constitutive relations from a finite number of lateral boundary measurements. Applying a Carleman estimate, the authors prove an estimate of the Lipschitz type for stability, provided that ε1,ε2,ε3,μ satisfy some a priori conditions.

关键词： Anisotropic media Inverse problem Maxwell's equations Carleman estimate Lipschitz stability

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