Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.32286/00022959

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media {LLC}  

DOI： 10.1007/s00707-019-02487-8

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Publishing type：Research paper (scientific journal)   Publisher：{IOP} Publishing  

DOI： 10.1088/2399-6528/aafc09

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Authorship：Lead author   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.aquaeng.2019.03.006

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Authorship：Corresponding author  

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J-GLOBAL

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Authorship：Corresponding author   Language：English   Publisher：The Physical Society of Japan  

We studied the single-arm spiral roll state in the system of Boussinesq fluid confined between nonrotating double concentric spherical boundaries with an opposing temperature gradient previously reported by Zhang et al. [<ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1103/PhysRevE.66.055203" xlink:type="simple">Phys. Rev. E <bold>66</bold>, 055203(R) (2002)</ext-link>]. It was found that the state exists even in a gap thicker than that used in this previous study, as an autonomously rotating wave solution with a finite constant angular velocity in a nonrotating geometry. We further confirmed that individual spiral roll states bifurcate directly from the static state at a number of intersections of the marginal stability curves. The double convective timescales peculiar to the state may involve global mixing through the entire domain albeit at the onset of convection, where a passive tracer geometrically explores through the entire spherical domain for sufficient time beyond a cell that would be formed by the other highly-symmetric steady states bifurcating at the onset.

DOI： 10.7566/JPSJ.84.103401

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

An outline of the state space of planar Couette flow at high Reynolds numbers (Re &lt; 10(5)) is investigated via a variety of efficient numerical techniques. It is verified from nonlinear analysis that the lower branch of the hairpin vortex state (HVS) asymptotically approaches the primary (laminar) state with increasing Re. It is also predicted that the lower branch of the HVS at high Re belongs to the stability boundary that initiates a transition to turbulence, and that one of the unstable manifolds of the lower branch of HVS lies on the boundary. These facts suggest HVS may provide a criterion to estimate a minimum perturbation arising transition to turbulent states at the infinite Re limit.

DOI： 10.1103/PhysRevLett.111.184502

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Quantitative evidence that establishes the existence of the hairpin vortex state (HVS) [T. Itano and S. C. Generalis, Phys. Rev. Lett. 102, 114501 (2009)] in plane Couette flow (PCF) is provided in this work. The evidence presented in this paper shows that the HVS can be obtained via homotopy from a flow with a simple geometrical configuration, namely, the laterally heated flow (LHF). Although the early stages of bifurcations of LHF have been previously investigated, our linear stability analysis reveals that the root in the LHF yields multiple branches via symmetry breaking. These branches connect to the PCF manifold as steady nonlinear amplitude solutions. Moreover, we show that the HVS has a direct bifurcation route to the Rayleigh-Benard convection.

DOI： 10.1103/PhysRevE.82.066308

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

A numerical continuation method has been carried out seeking solutions for two distinct flow configurations, planar Couette flow (PCF) and laterally heated flow in a vertical slot (LHF). We found that the spanwise vortex solution in LHF identifies a new solution in PCF. The vortical structure of our new solution has the shape of a hairpin observed ubiquitously in high-Reynolds-number turbulent flow, and we believe this discovery may provide the paradigm for a hierarchical organization of coherent structures in turbulent shear layers.

DOI： 10.1103/PhysRevLett.102.114501

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

DOI： 10.1007/978-3-642-03085-7_156

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：BEGELL HOUSE, INC  

This document describes briefly the homotopy route via which the Hairpin Vortex Solutions (HVS) were recently discovered. The bifurcation sequence starts from the geometrical configuration that is applicable to lateral heating in a vertical channel of infinite extent. Such a system has been studied before and in this note we expose its connection to the turbulent ubiquitous structure of the HVS.

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Language：English   Publisher：THE PHYSICAL SOCIETY OF JAPAN  

An ideal of osmotic equilibrium between an ideal solution and pure solvent separated by a semi-permeable membrane is studied numerically using the method of molecular dynamics. The osmotic flow is observed as the inflow of the solvent across the membrane from the dilute to the concentrated side. The validity of van&rsquo;t Hoff&rsquo;s law for osmotic pressure is confirmed over a wide range of concentrations. It is found that the law is established by a balance between non-uniform partial pressures of solute and solvent. Furthermore, the present model permits an understanding of the mechanism of the osmotic flow in the relaxation process as the liquids evolve from the initial state to the equilibrium state. We focus in particular on the interaction between solute and solvent.

DOI： 10.1143/jpsj.77.064605

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science Council of Japan  

With the aid of molecular dynamics, osmotic equilibrium between ideal solution and pure solvent separated by semi-permeable membranes is investigated numeri- cally. The method using phantom molecules is developed to model the membranes reflecting solute molecules. The validity of van't Hoff law for the osmotic pressure is confirmed over a range of concentration up to 0.1 in mole fraction.

DOI： 10.11345/nctam.56.357

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

Direct numerical simulation of a turbulent channel flow in a periodic domain of relatively wide spanwise extent, but minimal streamwise length, is carried out at Reynolds number R.e(tau) = 349. The large-scale structures previously observed in studies of turbulent channel flow using huge computational domains are also shown to exist even in the streamwise-minimal channel of the present work. In the system, it is also clearly observed how the large-scale structures and the near-wall structures affect each other. While the collective behaviour of near-wall structures enhances a large-scale structure, the resulting large-scale structure in turn activates the generation and drift of the latter. Hence near-wall and large-scale structures interact in a co-supporting cycle.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

Direct numerical simulation of a turbulent channel flow in a periodic domain of relatively wide spanwise extent, but minimal streamwise length, is carried out at Reynolds numbers Re-tau = 137 and 349. The large-scale structures previously observed in studies of turbulent channel flow using huge computational domains are also shown to exist even in the streamwise-minimal channels of the present study. Moreover, the limitation of the streamwise length of the domain enforces the interaction between large-scale structures and near-wall structures, which consequently makes it tractable to extract a simple cycle of processes sustaining the structures in the present channel flow. It is shown that the large-scale structures are generated by the collective behaviour of near-wall structures and that the generation of the latter is in turn enhanced by the large-scale structures. Hence, near-wall and large-scale structures interact in a co-supporting cycle.

DOI： 10.1017/S002211200400237X

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

Direct numerical simulation of a turbulent channel flow in a periodic domain of relatively wide spanwise extent, but minimal streamwise length, is carried out at Reynolds numbers Re-tau = 137 and 349. The large-scale structures previously observed in studies of turbulent channel flow using huge computational domains are also shown to exist even in the streamwise-minimal channel of the present work. In the system, it is also clearly observed how the large-scale structures and the near-wall structures affect each other. While the collective behavior of near-wall structures enhance a large-scale structure, the resulting large-scale structure in turn activates the generation and drift of the latter. Hence near-wall and large-scale structures interact in a co-supporting cycle. The preliminary numerical results suggesting the existence of traveling wave solutions that correspond to large-scale structures are reported.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

We search channel flow for unsteady solutions for different Reynolds numbers and configurations by extending a shooting method which was previously used to obtain a travelling-wave solution. A general initial condition is considered. A periodic-like solution to the incompressible Navier-Stokes equations in a minimal flow unit is found. One cycle of the solution consists of two typical intervals: a single-streak period and a double-streak period. The solution seems to be periodic; however, it cannot be distinguished from a heteroclinic cycle which consists of two heteroclinic orbits connecting two single-streak solutions, because the solution is tracked only for one and half periods.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

We have examined bursting processes observed in turbulent channel flow by direct numerical simulation of the incompressible Navier-Stokes equations in a minimal flow unit. A traveling wave solution (TWS) is obtained by a shooting method. The TWS corresponds to a saddle point in a two-dimensional phase space. A low-dimensional dynamics confined to the near-wall region is proposed in terms of the TWS and its manifolds. The characteristics of the coherent structures constituting the TWS are investigated dynamically and statistically in detail. The dynamics well describes an elementary process of intermittent turbulent regeneration in wall turbulence.

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

Direct numerical simulations (DNS) for the incompressible Navier-Stokes equations are employed to study three-dimensional plane Poiseuille turbulent flow (Re=3000). A traveling wave solution (TWS) is found. A scenario of turbulent production is proposed in terms of the TWS and its manifolds. It is concluded that a low-dimensional dynamics confined to near-wall region exists in the scenario and plays an active role in turbulent production and maintenance.

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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

Abstract: We employ a homotopy method, rather than conventional stability theory, in order to resolve the degeneracy due to resonance, which exists in fluid motion associated with a channel of infinite extent in ventilated double glazing. The introduction of a symmetry breaking perturbation, in the form of a Poiseuille flow component, alters substantially the resonant bifurcation tree of the original flow. Previously unknown resonant higher order nonlinear solutions, i.e. after the removal of the perturbative Poiseuille flow component, are discovered. A possible extension of the methodology to consider non-Newtonian gradient enhanced incompressible viscous fluids is also briefly discussed.

DOI： 10.1134/S1995080221080035

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Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevFluids.6.L072301

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Publishing type：Research paper (international conference proceedings)  

The shooting method, which was established originally as a tool to find out an unstable steady solution of subcritical shear flows (cf. J. Phys. Soc. Jpn. 70, 703 [1]), is applied to outline a structural aspect of laminar-turbulent transition of minimal plane Couette flow at the moderate Reynolds number. By adopt as initial conditions the points on the plane in phase space spanned by three distinct exact steady solutions, including the Hairpin Vortex Solution (HVS, cf. Phys.Rev.Lett.102,114501 (2009)), a plenty of trial calculations based on the method are carried out. The result implies that HVS is on the boundary separating the laminar and the turbulent attractors of the plane Couette flow, and that one of the unstable manifolds of HVS constitutes the boundary. Moreover, the asymptotic behaviour of HVS at higher Reynolds number is investigated, which enables us to quantify the role of HVS in the laminar-turbulent transition of Plane Couette flow at the moderate Reynolds number.

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DOI： 10.3233/BIR-201010

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Publishing type：Research paper (international conference proceedings)  

In this work we investigate pattern formation in the hierarchical transition to turbulence through the resonant nonlinear interaction between stationary states or travelling wave modes with wave numbers in the ratio 1:2, 1:3 and 1:4 for the case of LHF without PFC, while we also present results for 1:2 and 1:3 strongly nonlinear resonance in LHF with PFC.

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DOI： 10.1103/PhysRevFluids.4.124307

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press  

An experimental and numerical study on the inertial focusing of neutrally buoyant spherical particles suspended in laminar circular tube flows was performed at Reynolds numbers ranging from 100 to 1000 for particle-To-Tube diameter ratios of . In the experiments, we measured the cross-sectional distribution of particles in dilute suspensions flowing through circular tubes several hundreds of micrometres in diameter. In the cross-section located at 1000 times the tube diameter from the tube inlet, all particles were highly concentrated on one annulus or two annuli, depending on . At low , the particles were focused on the so-called Segré-Silberberg (SS) annulus, in accordance with previous studies (regime (A)). At higher , two particle focusing annuli appeared, with the outer annulus corresponding to the SS annulus (regime (B)). We call the annulus closer to the tube centre 'the inner annulus', although this term was used by Matas et al. (J. Fluid Mech., vol. 515, 2004, pp. 171-195) for a significantly broader annulus which included the transient accumulation of particles observed in regime (A). At even higher , particles were focused on the inner annulus (regime (C)), indicating that the radial position of the SS annulus is no longer a stable equilibrium position. These experimental results were confirmed by a numerical simulation based on the immersed boundary method. The results of this study also indicate that the critical Reynolds numbers between two neighbouring regimes decrease with the increase of the particle-To-Tube diameter ratio.

DOI： 10.1017/jfm.2019.325

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

Background: In the microcirculation, red blood cells (RBCs) were observed to be confined to an axial stream surrounded by a marginal RBC depleted layer. This axial accumulation of RBCs is considered to arise from the RBC deformability. Objective: To quantitatively evaluate the effect of RBC deformability on their axial accumulation at a flow condition comparable to that in arterioles by developing a new observation system for accurate measurements of radial RBC positions in the cross section of capillary tubes. Methods: The cross-sectional distributions of normal and hardened RBCs as well as softened RBCs suspended in capillary tube flows were measured with high spatial resolution. A new observation system was developed in which enface views of the cross-section of the tube were obtained at small distances upstream of the outlet at various longitudinal positions in the tube. Results: The radial positions of individual RBCs were detected within 1 μm accuracy. It was found that normal and softened RBCs rapidly migrated away from the wall towards the tube axis, whereas glutaraldehyde-hardened RBCs were dispersed widely over the tube cross-section, depending on the concentration of glutaraldehyde solution. Conclusions: The newly devised observation system revealed quantitatively the essential role of RBC deformability in their axial accumulation.

DOI： 10.3233/BIR-18166

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

The inertial migration of neutrally buoyant spherical particles suspended in tube flows of square cross sections was investigated experimentally in the range of Reynolds numbers (Re) from 1 to 800 for particle-to-tube-size ratios from 0.075 to 0.175. Direct observations of the particle distribution in the cross section at various distances from the tube inlet revealed that at low Re, smaller than a certain critical value, particles were focused on four equilibrium positions, located at the center of channel faces, consistent with previous studies on microchannel flows, whereas at higher Re, larger than another critical value, four additional equilibrium positions were observed near the channel corners. At intermediate Re, between these two critical values, we observed new focusing positions of particles, located on a heteroclinic orbit joining the channel face and corner equilibrium positions. Comparing these results with corresponding numerical simulations, we examined the migration properties in detail and categorized their types. It was found that the critical Re values depended considerably on the particle-to-tube-size ratio.

DOI： 10.1103/PhysRevFluids.2.044201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

An experimental study of the inertial migration of neutrally buoyant spherical particles suspended in the Poiseuille flow through circular tubes has been conducted at Reynolds numbers (Re) from 100 to 1100 for particle-to-tube diameter ratios of similar to 0.1. The distributions of particles in the tube cross-section were measured at various distances from the tube inlet and the radial probability function of particles was calculated. At relatively high Re, the radial probability function was found to have two peaks, corresponding to the so-called Segre Silberberg annulus and the inner annulus, the latter of which was first reported experimentally by Matas el al. (J. Fluid Mech. vol. 515, 2004, pp. 171-195) to represent accumulation of particles at smaller radial positions than the Segre Silberherg annulus. They assumed that the inner annulus would he an equilibrium position of particles, where the resultant lateral force on the particles disappears, similar to the Segre Silberberg annulus. The present experimental study showed that the fraction of particles observed on the Segre Silberberg annulus increased and the fraction on the inner annulus decreased further downstream, accompanying an outward shift of the inner annulus towards the Segre Silberherg annulus and a decrease in its width. These results suggested that if the tubes were long enough, the inner annulus would disappear such that all particles would be focused on the Segre Silberberg annulus for Re &lt;1000. At the cross-section nearest to the tube inlet, particles were absent in the peripheral region close to the tube wall including the expected Segre Silberberg annulus position for Re &gt; 700. In addition, the entry length after which radial migration has fully developed was found to increase with increasing Re, in contrast to the conventional estimate. These results may he related to the developing flow in the tube entrance region where the radial force profile would he different from that of the fully developed Poiseuille flow and there may not he an equilibrium position corresponding to the Segre Silberherg annulus.

DOI： 10.1017/jfm.2016.881

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The transition of laterally heated flows in a vertical layer and in the presence of a streamwise pressure gradient is examined numerically for the case of different values Prandtl number. The stability analysis of the basic flow for the pure hydrodynamic case (Pr = 0) was reported in [1]. We find that in the absence of transverse pumping the previously known critical parameters are recovered [2], while as the strength of the Poiseuille flow component is increased the convective motion is delayed considerably. Following the linear stability analysis for the vertical channel flow our attention is focused on a study of the finite amplitude secondary travelling-wave (TW) solutions that develop from the perturbations of the transverse roll type imposed on the basic flow and temperature profiles. The linear stability of the secondary TWs against three-dimensional perturbations is also examined and it is shown that the bifurcating tertiary flows are phase-locked to the secondary TWs. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.chaos.2016.07.012

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Language：Japanese   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.71.2.0_2689

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

The lateral migration properties of a rigid spherical particle suspended in a pressure-driven flow through channels with square cross-sections were investigated numerically, in the range of Reynolds numbers (Re) from 20 to 1000. 'The flow field around the particle was computed by the immersed boundary method to calculate the lateral forces exerted on the particle and its trajectories, starting from various initial positions. 'The numerical simulation showed that eight equilibrium positions of the particle are present at the centres of the channel faces and near the corners of the chatmel cross-section. 'Me equilibrium positions at the centres of the channel faces are always stable, whereas the equilibrium positions at the corners are unstable until Re exceeds a certain critical value, Re-e. At Re Re-e additional equilibrium positions appear on a heteroclinic orbit that joins the channel face and corner equilibrium positions, and the lateral forces along the heteroclinic orbit are very small. As Re increases, the channel face equilibrium positions are shifted towards the channel wall at first, and then shifted away from the channel wall. The channel corner equilibrium positions exhibit a monotonic shift towards the channel corner with increasing Re. Migration behaviours of the particle in the cross-section are also predicted for various Values of Re. rftlese numerical results account for the experimental observations of particle distributions in the cross-section of micro and millimetre scale channels, including the characteristic alignment and focusing of the particles, the absence of the corner equilibrium positions at low Re and the progressive shift of the equilibrium positions with Re.

DOI： 10.1017/jfm.2015.456

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

DOI： 10.11316/jpsgaiyo.70.1.0_3143

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Cambridge University Press  

The inertial migration of neutrally buoyant spherical particles in square channel flows was investigated experimentally in the range of Reynolds numbers (Re) from 100 to 1200. The observation of particle positions at several cross-sections downstream from the channel entrance revealed unique patterns of particle distribution which reflects the presence of eight equilibrium positions in the cross-section, located at the centres of the channel faces and at the corners, except for low Re. At Re smaller than approximately 250, equilibrium positions at the corners are absent. The corner equilibrium positions were found to arise initially in the band formed along the channel face, followed by a progressive shift almost parallel to the side wall up to the diagonal line with increasing Re. Further increase in Re moves the corner equilibrium positions slightly toward the channel corner, whereas the equilibrium positions at the channel face centres are shifted toward the channel centre. As the observation sites become downstream, the particles were found to be more focused near the equilibrium positions keeping their positions almost unchanged. These lateral migration behaviours and focusing properties of particles in square channels are different to that observed in microchannels at lower Re and to what would be expected from extrapolating from the results for circular pipes at comparable Re.

DOI： 10.1017/jfm.2014.232

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Publishing type：Research paper (international conference proceedings)  

The shooting method is employed to outline a structural aspect of phase space of plane Couette flow, associated with laminar-Turbulent transition at moderate Reynolds numbers (Re ∼ 104). The basin boundary separating the laminar and the turbulent attractors in the phase space is emerged out of trajectories starting from initial conditions constituted by superposition of three distinct exact steady solutions of PCF, including the Hairpin Vortex Solution (Itano & Generalis (2009); Gibson et al. (2009)) and the so-called Nagata's solution (Nagata (1990)). The result implies that HVS is on the basin boundary even at moderate Reynolds numbers, and that one of the unstable manifolds of HVS heads towards the NBW, which lies on the basin boundary.

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

In order to improve the record of the javelic throw in the junior Olympic games, it is important to elucidate the flight characteristics of the "turbo-jav" used in this throwing event. Unlike the spear used in the javelin throw, the turbo-jav has four tail fins. Focusing on the effect of the fins, we investigate the flight characteristics of the turbo-jav, by means of wind tunnel tests, throwing experiments and numerical simulations. In the wind tunnel test, we measured the drag force, lift force and pitching moment acting on intact turbo-javs as well as turbo-javs with their fins cut, in a low speed wind tunnel at the flow speed up to 25 m/s. The experimental results showed that the drag and lift coefficients for the intact turbo-javs are larger than the corresponding values for the turbo-javs without fins. As the angle of attack increases from 0, the moment coefficients for the intact turbo-javs decrease from 0, whereas the moment coefficients for the turbo-javs without fins increase. In accord with this property for the pitching moment, the throwing experiments showed that intact turbo-javs fly stably with oscillating angle of attack around 0. The flying distance, the orbit and the variation of angle of attack for the intact turbo-javs launched by a launcher agree closely with the numerical simulation performed based on the wind tunnel test. A comparison of throwing experiments by an athlete and by the launcher suggested that the turbo-javs flying without rolling could reach farther than turbo-javs with rolling.

DOI： 10.1299/kikaib.79.1561

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

An electrostatic model is developed for osmotic flow across a layer consisting of identical circular cylinders with a fixed surface charge, aligned parallel to each other so as to form an ordered hexagonal arrangement. The expression of the osmotic reflection coefficient is derived for spherical solutes with a fixed surface charge suspended in an electrolyte, based on low-Reynolds-number hydrodynamics and a continuum, point-charge description of the electric double layers. The repulsive electrostatic interaction between the surface charges with the same sign on the solute and the cylinders is shown to increase the exclusion region of solute from the cylinder surface, which enhances the osmotic flow. Applying the present model to the study of osmotic flow across the endothelial surface glycocalyx of capillary walls has revealed that this electrostatic model could account well for the reflection coefficients measured for charged macromolecules, such as albumin, in the physiological range of charge density and ion concentration.

DOI： 10.1017/S0022112010003708

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

Using confocal microscopy, we studied the individual motion of fluorescent platelet-sized latex beads suspended in glycerol-PBS solution, flowing through a narrow gap of 80 um width in a PDMS-conical channel with a round ball inside. The trajectories and the velocity profiles of beads were investigated in the gap region, in the absence or presence of red cells at hematocrit 1%. The presence of red cells enhanced the fluctuations of the beads velocities and often deflected their trajectories from the streamlines of the suspension fluid, especially near the channel wall.

DOI： 10.11395/jjsem.10.s102

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The electrostatic model for osmotic flow across a porous membrane in our previous study (Akinaga et al. 2008)" was extended to include the streaming potential, for solutes and pores of like charge and fixed surface charge densities. The magnitude of the streaming potential was determined to satisfy zero current condition along the pore axis. It was found that the streaming potential affects the velocity profiles of the pressure driven flow as well as the osmotic flow through the pore, and decreases their flow rates, particularly in the case of large Debye length relative to the pore radius, whereas it has little effect on the reflection coefficients of spherical solutes through cylindrical pores.

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

An electrostatic model for osmotic flow through circular cylindrical pores is developed to describe the reflection coefficient for the membrane transport in the presence of surface charges on the pore wall and the solute. For a spherical solute placed at an arbitrary radial position in the pore, the electrical potential was computed by a spectral element method applied to the Poisson-Boltzmann equation together with the condition of electrical neutrality. The interaction energy between the surface charges was used to estimate the osmotic reflection coefficient. The proposed model predicts that even for a small Debye length compared to the pore radius, the repulsive electrostatic interaction between the surface charges could significantly increase the osmotic flow through the pore.

DOI： 10.1143/JPSJ.77.053401

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CAMBRIDGE UNIV PRESS  

A mathematical model is presented for steady fluid flow across microvessel walls through a serial pathway consisting of the endothelial surface glycocalyx and the intercellular cleft between adjacent endothelial cells, with junction strands and their discontinuous gaps. The three-dimensional flow through the pathway from the vessel lumen to the tissue space has been computed numerically based on a Brinkman equation with appropriate values of the Darcy permeability. The predicted values of the hydraulic conductivity LP, defined as the ratio of the flow rate per unit surface area of the vessel wall to the pressure drop across it, are close to experimental measurements for rat mesentery microvessels. If the values of the Darcy permeability for the surface glycocalyx are determined based on the regular arrangements of fibres with 6 nm radius and 8 nm spacing proposed recently from the detailed structural measurements, then the present study suggests that the surface glycocalyx could be much less resistant to flow compared to previous estimates by the one-dimensional flow analyses, and the intercellular cleft could be a major determinant of the hydraulic conductivity of the microvessel wall.

DOI： 10.1017/S0022112008000530

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science Council of Japan  

The luminal surface of capillmy walls is covered by a layer of macromolecules referred to as the glycocalyx. In order to examine the role of the glycocalyx in the microvessel permeability, we have estimated the transport property of the microvessel wall, by using a one-dimensional model for the solute exchange through a serial pathway of the glycocalyx and the interendothelial cleft. The model provided reasonable predictions for the diffusional permeability and the reflection coefficient for solutes up to the size of albt.nnin. The results suggest that the endothelial surface glycocalyx could form the primary molecular sieve in transcapillmy pathways.

DOI： 10.11345/nctam.56.373

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Science Council of Japan  

An electrostatic model for osmotic flow through channels with surface charges is developed to understand the contribution of electrical charges to the transport of solution through narrow channels. The interaction energy between surface charges of the solute and the channel wall is used to express the osmotic reflection coefficient as a fi.mction of the surface charges, the ion concentration of the fluid, and the size ratio of the solute to the channel. Our model predicts that even for small Debye length compared to the channel size, the surface charges could significantly increase the osmotic flow, when the charges of the solute and the channel wall have the same sign.

DOI： 10.11345/nctam.56.365

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Authorship：Lead author  

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Publishing type：Research paper (scientific journal)   Publisher：Fluid Mechanics and its Applications  

DOI： 10.1007/1-4020-4049-0_3

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Language：Japanese  

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

An outline of the state space of planar Couette flow at high Reynolds numbers (Re < 10^4) is investigated via a variety of efficient numerical techniques. It is verified from nonlinear analysis that the lower branch of Hairpin Vortex State (HVS) asymptotically approaches the primary (laminar) state with increasing Re. It is also predicted that the lower branch of HVS at high Re belongs to the stability boundary that initiates transition to turbulence. These facts suggest HVS may provide a criterion to estimate a minimum perturbation arising transition to turbulent states at the infinite Re limit.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The concentration of platelets in flowing blood is known to attain maximum near the vessel wall, and this phenomenon is referred to as "Near Wall Excess (NWE)". Although NWE is evidently important and expedient in hemostatic functions of the platelets, its mechanism has not been fully elucidated yet. In order to understand NEW from a mechanical point of view, we measured the distribution of platelet-sized latex beads in a mixed suspension with human red cells flowing through microchannels, by using a confocal laser scanning microscope. The results indicated that the distributions of beads of various diameters were nonuniform in the presence of red cells, whereas their distributions in the absence of red cells were uniform in the channel cross-section. In the mixed suspensions of beads and red cells, the concentration profiles of beads of 3μm diameter showed sharp peaks near the channel walls at hematocrits of 20% and 44%, and the extent of this NWE was larger for larger hematocrits in the range examined. On the other hand, the beads of 1μm diameter exhibited NWE only slightly at similar hematocrits, and instead, they showed a distinct tendency to concentrate near the channel centerline.

CiNii Books

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Language：English   Publisher：SPRINGER-VERLAG BERLIN  

Web of Science

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Language：Japanese  

Direct numerical simulations of a turbulent channel flow have been performed with several streamwise domains at Re_τ=1020 to examine the effects of the computational domain size on turbulence quantities. It is shown that the effects of the domain size appear at the streamwise domain size less than 1.6δ, whereas they do not appear noticeably at the streamwise domain size of 3.2δ, which is closely associated with the behavior of pressure fluctuations.

CiNii Books

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Language：Japanese   Publisher：京都大学  

CiNii Books

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Other Link： http://hdl.handle.net/2433/47796

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

Web of Science

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Language：Japanese   Presentation type：Oral presentation (general)  

Venue：愛知  

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Venue：Seattle, Washington  

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Venue：Seattle, Washington  

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Language：English   Presentation type：Oral presentation (general)  

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Venue：大阪大学  

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Venue：東京理科大  

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Venue：東京理科大  

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Venue：Denver, Colorado  

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Venue：Denver, Colorado  

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Venue：Denver, Colorado  

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Venue：東京理科大  

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Venue：東京理科大  

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Venue：東京理科大  

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Venue：関西大学 千里山キャンパス  

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Venue：大阪大学 豊中キャンパス  

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Venue：Portland, Oregon  

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Venue：Portland, Oregon  

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Venue：Portland, Oregon  

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Venue：Portland, Oregon  

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Venue：Portland, Oregon  

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Venue：名古屋大学 御器所キャンパス  

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Venue：名古屋大学 御器所キャンパス  

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Venue：名古屋大学 御器所キャンパス  

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Venue：Kansai Seminar House , Kyoto  

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Venue：東北学院大学  

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Venue：Boston, Massachusetts  

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Venue：Boston, Massachusetts  

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Venue：Boston, Massachusetts  

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Venue：早稲田大学  

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Venue：Sotos’s invitation to Aston Univ, UK  

Sotos’s invitation to Aston Univ, UK. stay 2/25-3/9 (EAS visiting scholars fund 2014) 1 hour talk of my research

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Venue：CA, USA  

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Venue：CA, USA  

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Venue：CA, USA  

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Venue：Sanfrancisco, USA  

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Venue：東北大学川内キャンパス  

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Venue：東北大学川内キャンパス  

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Venue：東北大学川内キャンパス  

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Venue：東北大学, 宮城  

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Venue：東北大学, 宮城  

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Venue：Barcelona, Spain  

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Venue：関西大学  

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Venue：Lyon, France  

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Venue：Poitiers, France  

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Venue：奈良県文化会館  

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Venue：関西大学  

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Venue：北海道大学, 札幌  

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Venue：京都大学  

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Venue：理化学研究所, 東京  

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Venue：Stockholm  

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ISBN 88－7587－271－6

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