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Published: September 04, 2010
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Article type: Appendix
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Published: September 04, 2010
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Article type: Index
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A1-A6
Published: September 04, 2010
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Shinichiro YANASE, Shatat Mohammed M. E., Toshihiro TAKAMI
Article type: Article
Session ID: S0506-1-1
Published: September 04, 2010
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The effect of air micro-bubbles injected into water flowing through helical pipes with different curvature values (0.018, 0.027 and 0.045) on drug reduction and heat transfer performance were experimentally investigated. The mean diameter of the micro-bubbles generated was about 50μm with void fraction ranging from 0.09% to 0.25%. The effect of the Reynolds number is also presented in the range O(10^3)〜(10^5). The experimental results show that, the micro-bubbles have reduction effects in drag and heat transfer on the flows through helical pipes. However, the reduction in heat transfer was more significant than that in drag. It was found that both the heat transfer and drag reduction increase with the decrease of curvature and the increase of void fraction. The maximum value of drag reduction ratio obtained was about 17.6% in case of the lowest curvature coil, while the maximum heat transfer reduction for the same coil was 22.1%.
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Takashi OHTA, Hiroshi YASOSHIMA
Article type: Article
Session ID: S0506-1-2
Published: September 04, 2010
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Direct numerical simulations(DNS) of turbulent channel flow of surfactant solution are carried out, in order to reveal the mechanism of drag reduction by the effect of surfactants. The intensity of the streamwise vortices in surfactant solution is smaller than that in Newtonian fluid, although the streamwise component of velocity fluctuation is maintained. The results show that the effect of surfactant suppresses the distribution from the streamwise component of turbulence energy to the spanwise and the wall-normal components. In addition, large-eddy simulations(LES) with the Smagorinsky model are carried out in the flow field of surfactant solution. The results of LES are not corresponding to those of DNS.
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Koichi ARAGA, Koji HASEGAWA, Tatsuro WAKIMOTO, Kenji KATO
Article type: Article
Session ID: S0506-1-3
Published: September 04, 2010
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It is known that small quantities of surfactant additives can greatly reduce the friction factors during the flow of a heat transfer medium. The friction factors are reduced because the generation of turbulent vortices is suppressed by the formation of rod-like micelles, and the flow remains laminar in the high Reynolds number range. However, the values of heat transfer coefficients decrease during flow laminarization. The research objective is to study the heat transfer enhancement effect of micro-bubble injection. This paper presents an experimental investigation of the heat transfer and flow characteristics of an air-surfactant solution two-phase flow through a horizontal pipe. In the experiment, micro-bubble was injected through three types of porous metal. The experimental results are as follows. The flow patterns of air-surfactant solution two-phase flow depend on the size of micro-bubble. The heat transfer coefficient is promoted by micro-bubble injection, but the effect depends on the flow pattern or the size of micro-bubble.
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Satoshi SHIMADA, Naohisa TAKAGAKI, Koji IWANO, Ryoichi KUROSE, Satoru ...
Article type: Article
Session ID: S0506-1-4
Published: September 04, 2010
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Sensible heat transfer across the wind-driven air-water interface in the high speed wind region with breaking wave was investigated through laboratory experiments in a wind-wave tank. We proposed the water vapor balance method for estimating the sensible heat transfer velocity in the high speed wind region with breaking wave, in stead of the heat balance method available only in the low speed wind region. The sensible heat transfer velocity monotonically increases with the free stream wind speed in the high wind speed region with breaking wave. The results suggest that the effect of breaking wave on the sensible heat transfer across the wind-driven air-water interface is small.
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Naoki NISHIOKA, Kenji KATOH, Tatsuro WAKIMOTO
Article type: Article
Session ID: S0506-1-5
Published: September 04, 2010
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The similarity between turbulent heat transfer and Reynolds stress is investigated using the equations written in Lagrange description. The correlation between pressure gradient fluctuation in the flow direction and wall-normal velocity [term (B)] depress the Reynolds stress, which makes the turbulent Prandtl number Prt less than unity. Using the database of trajectories of fluid particles calculated by DNS, an algebraic equation was derived to correlate the term (B) to the discrepancy between average velocity and temperature distribution. The change of Prt with regard to (B) was estimated based on the equation. The slight decrease of (B) causes the dramatic reduction of Prt near the channel center. As (B) is further decreased, the range of Prt reduction extends to the smaller y, while the change of Prt in y^+<60 is hardly recognized. The pressure gradient-wall normal velocity correlation has a strong influence on the dissimilarity in the log-law region of y^+>60.
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Kenji KATOH, Akira SAKAI, Genta KAWAHARA
Article type: Article
Session ID: S0506-1-6
Published: September 04, 2010
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The dissimilarity between turbulent heat flux and Reynolds stress was investigated by using the results of numerical simulation for the channel flow. The dissimilarity may be strongly related to the transverse vorticity ω_z because the Reynolds stress could be suppressed during the swirl motion of the fluid particle. The transverse vortex was excited in the numerical simulation by imposing the streamwise force having the gradient in the wall-normal direction. A strong dissimilarity can be recognized especially in the upstream of the vortex center. The transverse vortex should be responsible for the dissimilarity in the turbulent flow, since the contribution to the overall dissimilarity is concentrated in the region where the strong swirl motion is observed.
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Debasish BISWAS, Tomohiko JIMBO
Article type: Article
Session ID: S0506-2-1
Published: September 04, 2010
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Numerical studies of 3-D incompressible viscous unsteady flow within an axial turbine stage are analyzed in this work. The flow exiting the combustor and entering the turbine of a gas turbine engine is known to contain both spatial and temporal variation in total temperature. Experimental results indicated that hotter fluid migrates toward the pressure surface and cooler fluid migrates towards the suction surface. The main purpose of this study is to test the performance of a high-order LES model in terms of predicting this type of highly complicated unsteady flow and heat transfer phenomena
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Hideki KAWANISHI, Yoshiharu NOBUTANI, Hirokazu MATSUOKA, Masahiko MITS ...
Article type: Article
Session ID: S0506-2-2
Published: September 04, 2010
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The behavior of the flame propagation in premixed methane-air of a main chamber was analyzed by using the LES turbulent, 2-scaler flamelet combustion flow simulation The flame shape is long and slender immediately after it flows into the main chamber. As the turbulence at the flame front grows, the flame extends horizontally and the flame structure becomes more complex. The effect of the diameter of the sub-chamber orifice of 4mm and 7mm was investigated. For the case of 4mm, the inflow velocity is higher and the flame shape is longer and more slender. The predicted flame behavior agreed well with the visualized experiments, it was shown that the present model is very feasible.
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Masafumi HIROTA, Tomoya MIYAKOSHI, Hiroki FUJINAGA, Shuichiro HORI, Hi ...
Article type: Article
Session ID: S0506-2-3
Published: September 04, 2010
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Experimental study was made on promotion and control of turbulent mixing of hot and cold airflows in a T-junction, which simulated an HVAC unit for automobile A/C system. Delta wings were used as a mixing promoter, and the influence of their attack of angles on the thermal mixing and flow field were examined in detail. It was found that the thermal mixing is promoted by longitudinal vortices and strong turbulence produced by the delta wings and its promotion can be controlled by changing the angle of attack of the wings. The detailed structure of the mixing interface between two flows was examined by POD.
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Takashi NISHIMURA, Kenji KATOH, Tatsuro WAKIMOTO
Article type: Article
Session ID: S0506-2-4
Published: September 04, 2010
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The efficiency of heat transfer η, i.e., the ratio between heat transfer enhancement and drag increase from a smooth channel, is discussed for the turbulent and laminar flows in a channel with a wing-type vortex generator (VG) installed on the wall. In this report, the effect of Prandtl number Pr on ηis mainly discussed. η decreases slightly in the turbulent flow with Pr while it increases noticeably in the laminar flow. In the laminar flow, since there is no background turbulence in the smooth channel, the fluctuation generated by VG directly enhances the heat transfer, which is greater in high Pr region where the thermal diffusion effect is weakened. In addition, the increase of convective heat transfer near the wall has an important effect on the good efficiency for the laminar flow. The effect of down-flow around VG on η is discussed from the comparison with the numerical results for the channel without the notch hole just under the wing.
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Hiroyuki ABE, Yasuhiro MIZOBUCHI, Yuichi MATSUO
Article type: Article
Session ID: S0506-2-5
Published: September 04, 2010
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Direct numerical simulations of a zero-pressure gradient turbulent boundary layer have been performed in the range Re_θ=300〜1250 using the rescaling-recycling method where Re_θ is the Reynolds number based on the free stream velocity and the momentum thickness. In the present study, we report results on the effects of the recycling location on both turbulence statistics and structures. Also, a comparison with other numerical methods (viz. the fringe and passing wake methods) is made. It is shown that the present turbulence statistics are close to those obtained from the fringe method, whilst there is some discrepancy in results between the rescaling-recycling method and the passing wake method at low Reynolds numbers.
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M. MORI, S. TOMINAGA, M. KANEDA, K. SUGA
Article type: Article
Session ID: S0506-2-6
Published: September 04, 2010
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In order to understand the turbulent vortex production mechanism over porous walls, using the PIV experimental data, quadrant analyses and quadrant-hole analyses of the Reynolds shear stress are performed. The investigated flow fields are turbulent channel flows whose bottom walls are made of porous media. Three kinds of the porous media which have almost the same porosity but different permeability are used. From those analyses, it is found that the contribution of near-wall sweeps becomes the most dominant near the permeable wall while ejections tend to be weakened due to the wall permeability. As a result, longitudinal vortices hardly survive and transverse vortices, which used correspond to the vortex heads of hairpin or hook like vortices, develop over permeable walls.
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Koji FUKUDOME, Oaki IIDA, Yasutaka NAGANO
Article type: Article
Session ID: S0506-3-1
Published: September 04, 2010
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Direct numerical simulations of spectral method are performed to study the sustenance mechanism of large-scale structure in relaminarizing channel flow at a very low-Reynolds number. At a low-Reynolds number, the quasi-laminar and turbulent regions simultaneously appear and form the stripe pattern. The turbulent region is flanked by high- and low-speed fluids, which appear upstream and downstream of the turbulent region. The interface between quasi-laminar and turbulent regions features not only the intrusion of high-speed fluids into the downstream side, but also by redirection of streamwise velocity to the spanwise velocity. Thus, generated spanwise velocity becomes driving force for large-scale upward and downward flows which tilts the mean shear in the spanwise direction and contributes to generation and sustenance of the stripe pattern.
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Takahiro TSUKAHARA
Article type: Article
Session ID: S0506-3-2
Published: September 04, 2010
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This paper presents the direct numerical simulation (DNS) of various turbulent states and structures in a rotationg plane Couette flow. The formations of turbulent patterns or roll cells in the flow were investigated at Re=750 in a range of -30 ≤Ω≤30, using a large domain size of 204.8δx2δx102.4δ. The simulations reproduced many key features in the experiment of Tsukahara, Tillmark & Alfredsson (J. Fluid Mech., vol. 648, 2010, p. 5). For stabilizing rotation with Ω=-30, a striped pattern of inter-weaved laminar-turbulent regions was observed. For stabilizing rotation with Ω=30, we found that the turbulence seems to be contained in the three-dimensional roll cells.
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Takato IKEDO, Koji MORITA, Genta KAWAHARA, Sadayoshi TOH
Article type: Article
Session ID: S0506-3-3
Published: September 04, 2010
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Direct numerical simulations of fully developed turbulent flows in a horizontal plane channel heated from below are performed at low bulk Richardson numbers Ri<0.01 to examine buoyancy effects on turbulence structures. It is found that streamwise and wall-normal RMS velocities are increased by the effect of buoyancy in plane Couette flow at low Reynolds number Re = 400 and in plane Poiseuille flow at Re=2000, 3000, 4000. In larger- Re Couette turbulence (Re=750, 2000), on the other hand, only the streamwise RMS velocity is observed to be significantly intensified. In the former case the spanwise length scale of buoyancy-induced flow is close to that of near-wall streamwise vortices, leading to the enhancement of the wall-normal velocity fluctuation, while in the latter they are separated and thus no significant enhancement occurs.
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Genta KAWAHARA, Atsushi SEKIMOTO, Markus UHLMANN, Alfredo PINNELLI
Article type: Article
Session ID: S0506-3-4
Published: September 04, 2010
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Direct numerical simulations of fully developed turbulent flows in a horizontal square duct heated from below are performed at bulk Reynolds numbers Re_b = 3000, 4400 in the range of bulk Richardson numbers 0 ≤ Ri ≤ 1.03 to characterize turbulence- and buoyancy-driven mean secondary flow. It is observed that for 0.025 ≲ Ri ≲ 0.25 turbulence-driven secondary flow of a usual eight-vortex pattern is deformed by the effect of buoyancy into turbulence- and buoyancy-driven flow represented by single large-scale circulation and four corner vortices of opposite sense of rotation to the circulation. This remarkable structural difference in the corner regions can be interpreted in terms of combined effects, on instantaneous streamwise vortices, of the large-scale circulation and of the geometrical constraint by impermeable duct walls.
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Toshiyuki GOTOH, Takeshi WATANABE
Article type: Article
Session ID: S0506-3-5
Published: September 04, 2010
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Statistics of transfer flux of a passive scalar under the mean uniform scalar gradient convected by homogeneous isotropic steady turbulence are examined by using the high resolution direct numerical simulation. It is found that the Nusselt number is expressed by the time integral of the Lagrangian velocity autocorrelation in the direction of the mean scalar gradient and increases as ScR^2_λ which agrees well with the results of the direct numerical simulation, where Sc and R_λ are the Schmidt and Reynolds numbers, respectively. The one point probability density function (PDF) of the scalar flux is also examined and found to be negatively skewed exponential but insensitive to the variation of the Reynolds and Schmidt numbers. The PDF of the scalar flux is also theoretically examined and found to be in good agreement with the numerical results.
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Tatsuo USHIJIMA, Osami KITOH, Kazuo KATAYAMA
Article type: Article
Session ID: S0506-3-6
Published: September 04, 2010
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In turbulent Couette flows, there exists a large-scale streamwise vortical structure of which width is of the ordre of the channel height 2h. The vortical structure affects the streamwise velocity fluctuation. In this study, 32-channel I-type probe, which covers 6h in the spanwise direction, is used to examine the fluctuation of large-scale streak. Fluctuation of the large-scale streak in shorter period (5-10h) than those of which periodic lenth is 40-60h is identified. This fluctuation is closely related to the self-sustaing process found in minimal Couette flow simulation.
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Ken YAMAGISHI, Takatsune NARUMI, Tomiichi HASEGAWA
Article type: Article
Session ID: S0501-1-1
Published: September 04, 2010
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Flow characteristics of liquid crystalline polymer (LCP) solutions with carbon nano fibers (CNF) dispersed have been investigated experimentally. CNF with very high aspect ratio was dispersed in HPC 50 w% aqueous solution at 0.5 w%. A standard viscosity measurement with a rheometer was conducted and repeated. The second or third measurements were started after previous measurement in high shear rate region with almost no time lag. In the first measurement, the dispersed system showed relatively simple shear thinning viscosity without region 2 which appeared in the viscosity curve of LCP only. Decreased apparent viscosities were obtained in the low shear rate region in the repeated tests. It is considered that alignment structure of CNF was maintained in the succeeding measurements.
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Kazunori YASUDA, Towa HIRAYAMA, Yukiharu IWAMOTO, Motosuke SOGO
Article type: Article
Session ID: S0501-1-2
Published: September 04, 2010
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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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Masaru SUMIDA, Taro FUJIMOTO
Article type: Article
Session ID: S0501-1-3
Published: September 04, 2010
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An optical measuring method for evaluating the fiber concentration has been developed for flowing pulp-suspensions. This method was applied to a fully-developed steady flow in ducts with a square cross section. The obtained results clarify quantitatively, in a definite form, the distributions of the fiber concentration that has long been an interesting subject of discussion among researchers. And also this shows availability of the method. Furthermore, it is found that the flow mechanism of pulp-suspension in ducts can be classified into five patterns.
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Masato Nakamura, Hiroshi Yamaguchi, Munehiro Maeda
Article type: Article
Session ID: S0501-1-4
Published: September 04, 2010
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Non-linear viscoelastic Bingham fluid is a kind of non-Newtonian fluid with complicated physical properties, and it has many applications such as in pipe design in production factory. In the past years, in line with the Bingham fluid study, different forms of the constitutive equation have been proposed. However, there are still lack of consistence between those theoretical predictions and experimental data. One of the reasons may be contributed to the non-transparent property of the Bingham fluid leading to it very difficult to be visualized. In present study, a transparent Bingham fluid is made and visualization experiment is performed. It is hope the present study lay a base for the application of viscoelastic Bingham fluid in engineering.
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Tetsuya NUMAKAWA, Satoshi OGATA
Article type: Article
Session ID: S0501-1-5
Published: September 04, 2010
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Drag reduction due to bacterial cellulose suspensions with small environmental loading was investigated. Experiments were curried out by measuring the pressure drop of a pipe flow. It has been reported that the bacterial cellulose suspensions cause the drag reduction phenomena in the turbulent flow range. The fiber of bacterial cellulose forms complicated network in the suspension. It is obtained about 10 % in the maximum drag reduction ratio of the friction factor. Drag reduction ratio increases with increasing the concentration of bacterial cellulose suspension. The drag reduction effect of bacterial cellulose suspension becomes lower under mechanical shear.
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Ryota IMAIZUMI, Takayuki SAITO
Article type: Article
Session ID: S0501-1-6
Published: September 04, 2010
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The objective is to clarify the turbulence modulation induced by interaction between a bubble swarm and oscillating-grid decaying turbulence. In order to generate simultaneously ideally homogeneous isotropic turbulence and a sufficiently controlled bubble swarm. First, the homogeneous isotropic turbulence was formed by operating oscillating-grid in cylindrical acrylic pipe (height: 600 mm, inner diameter: 149 mm) filled with ion-exchanged and degassed water. Second, we stopped the oscillating-grid in arbitrary time after the homogeneous isotropic turbulence was achieved. A few moments later, well-controlled bubble swarm was launched into the decaying turbulence by using bubble generators. The bubble formation, bubble size and bubble-launch timing are controlled arbitrarily and precisely by the bubble generators. We applied visualization of bubble motion to clarify the effect of liquid motion on bubble motion and PIV measurement to clarify the turbulence modulation. From the results, the bubble motion was changed from zigzag motion to 3-dimensional motion in the decaying turbulence and the standard deviations of liquid-phase velocity in case which the bubble swarm launched in the decaying turbulence was finally smaller than that in case of only decaying turbulence.
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Ayumi ARITAKE, Shuichi IWATA, Hideki MORI, Tsutomu TAKAHASHI
Article type: Article
Session ID: S0501-2-1
Published: September 04, 2010
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We have developed the Pressure-Oscillating Defoaming for removing air bubbles from shear-thinning fluids. When two air bubbles are set vertically in a quartz cell filled with shear-thinning fluids, the lower-bubble rises faster than the upper bubble under pressure-oscillating field generated by pressing a rubber sheet at the bottom of the cell^<(1)>. However, this mechanism of the behavior has not been completely understood. By using liquid with a good photoelastic correlation and rheological property similar to the UCM model^(2), we try measuring the stress in the vicinity of small bubbles under pressure-oscillating field. In this study, a relation between the retardation and the distance from the bubble surface was measured experimentally.
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Takehiro YAMAMOTO, Junji SUZUKI
Article type: Article
Session ID: S0501-2-2
Published: September 04, 2010
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In aqueous solutions of CTAB, worm-like micelles are formed at concentrations above CMC. In addition when counter ion is added to a CTAB solution, worm-like micelles entangle and form networks, which show gel-like structures under some conditions. In the present study, investigated is the formation of gel-like structures when an aqueous solution of NaSal is injected into a flow of a CTAB solution in a circular channel. The condition at which the adhesion of a gel to a channel wall occurs relates both the concentration of NaSal and the velocity of CTAB solution. When the concentration is high, the adhesion can be observed at higher velocity.
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Takashi Koshiba, Takehiro Yamamoto
Article type: Article
Session ID: S0501-2-3
Published: September 04, 2010
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The purpose of this study is to examine properties of shear viscosity for surfactant solutions including organic additives. The measurement of shear property was performed with a cone-plate type of rheometer. The surfactant solution used for this experiment is a CTAB/NaSal solution having a ratio of concentration 1/7.7, and the organic additive is an isooctane(2,2,4-Trimethylpentane). In the measurement of dynamic viscoelasticity, the property of relaxation time depends on the concentration of additives. At the concentration of isooctane below 0.1 wt%, this result suggested that the micelle structure changed because of the solubilization of isooctane in the deep interior of micelle. However, when the concentration of isooctane increases further, it is deduced that the micelle structure becomes a different type from that of low concentrations.
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Shohei IWATA, Yuichiro NAGATSU, Shuichi IWATA, Yutaka TADA, Riolfo Lui ...
Article type: Article
Session ID: S0501-2-4
Published: September 04, 2010
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The term "Viscous fingering" is usually used to refer to the instabilities that occur at the interface when a more viscous fluid is displaced by a less viscous fluid.However, we succeed an experimental study of viscous fingering fully triggered by a chemical reaction involving a viscosity increase and decrease when a less viscous fluid is displaced by a more viscous fluid in a radial Hele-Shaw cell. This is done by making use of a polymer (polyacrylic acid , sodium polyacrylate) solution's dependence of viscosity on pH. We show that a difference in fingering patterns is observed, depending on whether the viscosity is increased or decreased by the reactions.
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Takeshi Suzuki, Hiroshi Mizunuma, Yukihiro Michiwaki, Katsuyoshi Nishi ...
Article type: Article
Session ID: S0501-2-5
Published: September 04, 2010
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This study discussed the relationship between fluid viscosity and swallowing flow. We simulated numerically the liquid bolus flow near the epiglottis using digitized 3D bolus geometry, which was constructed from coronal and sagittal video fluoroscopic examination. The temporal changes in the 3D bolus geometries were numerically analyzed as fluid flow. We discussed the movements and the inside velocity distributions of the bolus. The influence of the bolus viscosity on the bolus flow was also discussed.
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Kazuna MIYAMOTO, Hiroshi MIZUNUMA, Shigenobu SHIMADA
Article type: Article
Session ID: S0501-2-6
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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When some cosmetic base oil was applied, the oscillatory friction of 50 Hz was observed. It was revealed that this oscillation was caused by the vibration of the moving plunger. It depended on the surface characteristics and the oil viscosity if this vibration appeared or not. Preferable feeling was produced by the vibration. A piezo vibrator was appended to the virtual application device, with which the sensory test was conducted. This virtual application with the vibration also produced preferable feeling.
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Akiomi USHIDA, Tomiichi HASEGAWA, Takatsune NARUMI, Hiroshige UCHIYAMA
Article type: Article
Session ID: S0501-3-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Jet thrusts and pressure drops of several kinds of liquids issuing through small orifices were measured and compared with the predictions from numerical analyses of the Navier-Stokes equations. Reasonable agreements for so-called Newtonian fluids were obtained between the experimental and predicted thrusts and pressure drops for orifices with openings of the order of 1OOμm size, but the experimental results were found to be below the predictions for orifices of the order of 1Oμm. It was suggested that water and glycerol solutions have an elastic property for elongational flows passing through small orifices.
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Tomiichi HASEGAWA, Akiomi USHIDA, Takatsune NARUMI
Article type: Article
Session ID: S0501-3-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Behavior of water flow through micro-apertures has scarcely examined in the region of very stow velocity. We measured velocities against pressures for the water flow through 25micron-meter orifice in a range of low velocity and low Reynolds number(Re=0〜20). It was found that a small difference in water temperature results in a great change in flow characteristics. That is, water flows with about two times larger velocities than the velocity theoretically predicted at 22 degree of Celsius temperature, but water lessens its velocity with time passed and goes to a very small velocity, and at last almost clogs itself 70hours after inception of experiment
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Satoshi OGATA, Shoko TAKAHAHSI
Article type: Article
Session ID: S0501-3-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The velocity profile of dilute polymer solutions and a distilled water near the wall surface in a microchannel was clarified using evanescent wave illumination. Fluorescent particles with the diameter of 20 nm were used as tracer particles. The test polymers are polyethylene-oxide (SE-5, SE-15, SE-30 and SE-70) solution at 5 ppm. The results obtained for the velocity profile of a distilled water was found that the resolution of the velocity profile near the wall surface was drastically improved from the conventional results. On the other hand, the velocity profile of dilute polymer solutions increased significantly compared with that of distilled water, and the gradient of the velocity profile increased with the increase of the molecular weight of polymer.
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Toshiyuki HORIKAWA, Takatsune NARUMI, Tomiichi HASEGAWA
Article type: Article
Session ID: S0501-3-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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We have investigated the mixing property of two liquids in micro channels where at least one of the liquids has viscoelasticity. As the first stage of this study, we have examined two types of T-shaped channels of millimeter order, i.e. a smooth channel and a channel with blocks at the mixing region. Colored water and sodium polyacrylate aqueous solutions of 100ppm and 1000ppm were tested and saturation of the dye diffused was measured. In the smooth T-shaped channel, polymer solutions with high viscosity were difficult to mix with water. However, in the T-shaped channel with blocks, high mixing efficiency was obtained even at low flow rates by utilizing polymer solutions. It is considered that Barus effect generated after the blocks with elastic properties of the polymer solutions improved the mixing in the flow.
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Shinji TOGA, Takatsune NARUMI
Article type: Article
Session ID: S0501-3-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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In this report, we observed the structure transition of colloidal dispersion in a contraction and expansion flow cell between two parallel plates separated by a small gap. In the study, we used a spectroscopic method to estimate the flow effects on the crystallization. The result shows the flow contraction encourages the crystal-lization in relatively-rapid flow, on the other hand, the flow expansion has a complex effect on it.
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Tsutomu TAKAHASHI, Kaoru INOUE
Article type: Article
Session ID: S0501-4-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Application and drying processes of chromonic liquid crystal solutions are investigated. Retardation and Nagaoka University of Technologyextinction caused by the shear flow in the application region are measured. The extinction exhibits a small fluctuation but the retardation shows a steady value. The polarized microscopic observation is also carried out. On the flow in the application process, the aggregates of the chromonic dye are oriented and generate a macroscopic structure. The small fluctuation in the extinction originates in the macroscopic structures.
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Tomoihro TSUJI, Shigeomi CHONO
Article type: Article
Session ID: S0501-4-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The velocity profile of backflow in a hybrid anchoring nematic liquid crystalline cell is experimentally and numerically analyzed to investigate the effect of initial molecular configuration on the backflow. From the results, it is found that there are two stages with different time scales of the backflow development. One is the rapid increase of the flow just after applying of an electric field, and the other is the transition of the back flow profile. While the transition occurs in the time scale of several tens of milliseconds, the increase occurs in several microseconds. Since the hybrid anchoring cell effectively create the backflow. it must be useful for the liquid crystal applications which utilize the backflow, such as liquid crystalline actuators.
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Shigeomi CHONO, Tomohiro TSUJI
Article type: Article
Session ID: S0501-4-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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For the purpose of developing liquid crystalline microactuators, we have proposed a one-dimensional simple model which combines the motion of the upper plate of a liquid crystal cell and the flow of a liquid crystal. The model is able to predict qualitatively the motion of the upper plate. We have studied the rotation of the director and it is clarified that when the electric field is released, the molecule at the middle position between two plates returns to the initial angle completely at 1 Hz of the frequency of the applied voltage, it does not return to the initial angle but it takes approximately 40 deg at 10 Hz, and it oscillates between 90 deg and 96 deg. at 100 Hz. The so-called kickback effect is dominant in this oscillation with small amplitude.
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Yuhiro IWAMOTO, Xiao-Dong NIU, Hiroshi YAMAGUCHI
Article type: Article
Session ID: S0501-4-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Temperature sensitive magnetic fluid (TSMF) has a property of magnetization dependent on temperature subjected to an applied magnetic field. In the present study, a binary magnetic fluid, which is a mixture of the TSMF and an organic secondary fluid, is utilized in a heat transport device to enhance its circulation. In order to verify the performance of the TSMF mixture in the heat transport device, the driving characteristics of this heat transport device are studied both experimentally and numerically. From the results it is found the driving force is enhanced greatly when the magnetic field intensity increases.
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Xiao-Dong Niu, Hiroshi Yamaguchi, Xin-Rong Zang, Yuhiro Iwamoto
Article type: Article
Session ID: S0501-4-5
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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Rheological characteristics of different viscoelastic magnetic fluids (VMF) are investigated experimentally in the present work. The test VMF is a mixture of a magnetic fluid and a viscoelastic fluid with different mass ratios. Studies show that the viscosity of VMF not only varies with external magnetic field, but also the mass ratio of the magnetic fluid in VMF. Most importantly, we found that the first normal stress difference that VMF act on the magnetic cone of rheometer decreases with increase of the magnetic field, and it becomes negative at low shear speed.
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Masaharu Kamata, Shinichiro ITO, Kazuya SEO, Takeshi ASAI
Article type: Article
Session ID: S0504-1-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The panel architecture of the soccer balls used in the World Cup has changed in every four years' convention. It is understood that the change in the panel structure in the soccer ball exerts a big influence on the aerodynamic characteristics. It is well known that the non-rotatinal shot by "TeamGeist" appeared in 2006 becomes a oscillating ball in the long or middle distance shot. However, the aerodynamic characteristics of the 2010 official ball, "JABULANI" has not been reported yet. In this study, the aerodynamic characteristics of "JABULANI"in the non-rotational shot and the possibility of the blur ball are verified.
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Katsumi AOKI, Koji MUTO, Hiroo OKANAGA, Shuzo MATSUNO, Ryutaro OGAWA
Article type: Article
Session ID: S0504-1-2
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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New official volleyball made by Mikasa Co. Ltd. was used in the volleyball game of the Beijing Olympics. However, the report for aerodynamic characteristics of the new official volleyball has not been done until now. In this report, comparison of aerodynamic characteristic of official volleyball used until now and new official volleyball adopted in the Beijing Olympics (2008) is carried out. From these results, we clarify an aerodynamic characteristics for rotation and unrotation of new official volleyball and old official volleyball.
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Koji MUTO, Hiroo OKANAGA, Katsumi AOKI
Article type: Article
Session ID: S0504-1-3
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The present study investigated the aerodynamic characteristics and flow pattern of a golf ball with 328 circular arc dimples. The aerodynamic forces and the flow pattern around a golf ball were investigated experimentally. The detailed flow pattern around a golf ball was then investigated computationally by Large eddy simulation. The aerodynamic characteristics and the flow pattern of a golf ball with rotation were clarified. In addition, the flying distance was clarified through a flying simulation based on the aerodynamic forces and the flow pattern.
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Yusuke EJIRI, Motomu NAKASHIMA
Article type: Article
Session ID: S0504-1-4
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The objective of this study was to measure the unsteady fluid force acting on the human body during swimming. For this objective, swimmer mannequin whose size was the half of the actual swimmer was conducted. An experiment to measure the drag acting on the mannequin was conducted in a circulating water tank. The mannequin was driven by the underwater driving device, and the drag was measured by four two-axis dynamometers. In the present report, the effect of rolling on the drag was investigated. From the experimental results, it was found that the drag increased once and decreased according to the increase of the rolling amplitude. However, since this result was found to be affected largely by the drag of bars supporting the mannequin, correction of the drag was attempt.
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Nobuhiro HAYASHI, Aiko TANAKA, Shouichiro IIIO, Toshihiko IKEDA
Article type: Article
Session ID: S0503-1-1
Published: September 04, 2010
Released on J-STAGE: August 01, 2017
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The aim of this study was to develop an environmentally friendly nano-hydraulic turbine utilizing rapid and shallow streams. Previous result on same system was found that power coefficient of runner reaches at 0.18 because of stagnation of working fluid upstream and inside of runner. So we adopted open type cross-flow runner to solve the problem. In this study, it was investigated the optimum angle of blade and the relationship between the power performance and the clearance between the runner and the bottom wall of the channel and the thickness of water stream collide with runner. As a result, it was clarified that the power coefficient increases with decrease of the clearance, with increase of the thickness of water stream collide with runner, the optimized angle of blade is 24 degrees and the maximum power coefficient is 0.41.
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