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Published: September 12, 2009
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Article type: Appendix
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Article type: Appendix
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Article type: Index
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A1-A5
Published: September 12, 2009
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Yoshiki YOSHIDA, Masahiro MURAYAMA
Article type: Article
Session ID: G0501-1-1
Published: September 12, 2009
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The formation of a tip leakage vortex was discussed on the region where roll-up of the vortex occurs. This region is of special interest in a tip leakage vortex cavitation. We attempted to relate the inception cavitation number, σ_i, to the angle of attack, α. It was found that the inception in a tip leakage vortex cavitation should follow the relation, σ/α=const.
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Takuru SAITO, Toshihiro SAWAMURA
Article type: Article
Session ID: G0501-1-2
Published: September 12, 2009
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The high speed water jet under the water is one of the methods by which tiny bubbles are generated. In this study, the periodicity of the luminance profiles in the photos of the submerged water jet is investigated by FFT and the peaks obtained from the spectrum are called "gas-phase scale". Then, the effects of the various parameters (pressure, air supply rate, nozzle length) on the bubble diameter are examined. As a result, the gas-phase scale obtained from the process was as large as the bubble diameter. Moreover, it was shown that when the standoff distance increases, the gas-phase scale also increases.
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Atsumu IKEDA, Satoshi WATANABE, Takanari SUEFUJI, Akinori FURUKAWA, Ka ...
Article type: Article
Session ID: G0501-1-3
Published: September 12, 2009
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Unsteady cavitating flow around a flat plate hydrofoil was studied in order to investigate the effect of tip leakage vortex cavitation on the unsteady character of the cavitating flow. A two-dimensional flat plate hydrofoil having rounded leading and trailing edges with/without a tip claearance was tested for several angles of attack. The cavitating flow was filmed from the top and the side simultaneously using two high speed video cameras, and the unsteady static pressures just upstream and dovmstream of the hydrofoil were also simultaneously measured with the high speed video camera recording. It was found that, with the tip clearance, the partial cavity at the same cavitation number became more or less shorter and thinner than that without the tip clearance. Even under the existence of the tip leakage vortex cavity, the Strouhal number rule of the unsteady cavitating flow based on the attached cavity length still stood in our experiments.
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Naoki ONO, Yuta WATANABE
Article type: Article
Session ID: G0501-1-4
Published: September 12, 2009
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We have tested a new micromixing process utilizing movement of gas-liquid free interface. In this micromixer the bubbles are trapped on the wall of channel due to surface tension. It is expected that the expanded and deflated bubbles could increase the mixing efficiency by shortening the diffusion length and bonding the flow. Moreover, because shear stress does not work on gas-liquid free interface, this process will not increase pressure drop. We compared the mixing efficiency of the new micromixer with conventional Y flow mixer. The experimental result proved that the new micromixer is more efficient than Y flow mixer.
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Akira SAITO, Daishi NISHITANI, Sotoji ODAKE, Hiroshi SORA, Yuuya IIDA
Article type: Article
Session ID: G0501-1-5
Published: September 12, 2009
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The fluid characteristics of vertically upward micro-bubble flow through the rough-surfaced tube were investigated experimentally. An experiment was performed for the Reynolds number in the range of 1000 up to 20000. In our experiment, we measured average void ratio at the outlet of the tube and the frictional pressure loss through the tube of 20mm in ID. The surface wall inside test sections consisted of the tube with no roughness or with roughness. The micro-bubble flow was formed in micro bubbles of almost 60 micrometer in diameter. It was found that the micro-bubble flow can delay laminar-turbulent transition and then the friction factor has minimum value at Re_1=5000, and that the effect of roughness on friction factor has a negligible small, in other words, the friction-reduction effect of the micro-bubble flow is especially effective against roughness.
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Taku MITANI, Go MINOURA, Makoto KOMURA, Seiji HIRAI
Article type: Article
Session ID: G0501-1-6
Published: September 12, 2009
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Micro-bubbles have various useful features and are frequently used in many fields nowadays. Here, it is shown that over a certain size range of the bubbles, they don't keep their sizes even for minutes. Then, attention is restricted to vanishing time of micro-bubbles in terms of fluid properties. Bubble life is found to be lengthened by both increasing kinematic viscosity and surface -tension coefficient.
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Tadashi WATANABE
Article type: Article
Session ID: G0501-2-1
Published: September 12, 2009
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Oscillating-rotating liquid droplets are simulated numerically using the level set method, and the relation between the droplet shape and the oscillation frequency is studied. It is shown that the frequency of shape oscillation increases as the average droplet shape is a rotating ellipsoid, while it decreases as the average shape is a vertically elongated ellipsoid. The frequency shift is found to become zero by controlling the amplitude and the rotation rate.
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Kenji NAKASHIMA, Yuuki JOHNO, Takahiro YAMAUCHI
Article type: Article
Session ID: G0501-2-2
Published: September 12, 2009
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When powder fomis a weak intemelion particle cluster in a gas-solid flow, the rate of fitil of the cluster exceeds the temiinal velocity of the individual particles. However, the relationship between the unsteady characteristics of the free-fall of the particle cluster and the geometric condition of the experiment is not clear. We performed the numerical analysis of the particle cluster that flee-gills in still air. The Hard Sphere Model and the Direct Numerical Simulation were used for the numerical analysis. The initial condition of the cluster is a ball of a diameter of 3.0mm and void fraction is 0.654. Reynolds number based on the cluster diameter is about 700. By this numerical simulation, the processes from the development to the decay of the particle cluster became clear. It was found that the particle cluster falling with ball shape changes to bowl shape along the flow pattern around the sphere and the decay begings with the lower edge of the centre axis.
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Koichi KITAMI, Takao INAMURA, Hideki YANAOKA, Minori SHIROTA, Yoshio N ...
Article type: Article
Session ID: G0501-2-3
Published: September 12, 2009
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The disintegration phenomena of a liquid jet issued from a co-axial injector of liquid rocket engine with recess was investigated experimentally using a transparent injector model with a rectangular cross section. In contrast to a previous research, the present injector has a gas flow channel at only one-side of liquid injection post, which prevents the liquid injection post from mechanical vibration. It was found that the atomization mechanism relates closely to a gas pressure in a recess. Critical Reynolds and Weber numbers were almost the same as those obtained by using a rectangular injector with a gas flow channel in both sides, that was used in a previous research.
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Masaki TSUSHIMA, Kazuki MATSUYAMA, Takao INAMURA, Hideki YANAOKA, Mino ...
Article type: Article
Session ID: G0501-2-4
Published: September 12, 2009
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The spray characteristics of a pre-filming air-blast atomizer was experimentally investigated by using a two-dimensional test atomizer. The breakup pattern of a liquid film at the atomizer tip was classified from instantaneous photographs. Drop size distribution was measured by using a particle size analyzer based on Fraunhofer diffraction method. Flux of spray flow was also evaluated using an isokinetic sampling probe. We clarified the breakup pattern change of a liquid film from liquid lump breakup to liquid ligament breakup with the increase of air velocity. This change in breakup pattern decreases a mean droplet diameter, while the normalized span-wise liquid flux distribution hardly changes; the liquid flux has maximum value at the center and approximately 15 % lower at both sides of the atomizer.
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Takayuki IGARASHI, Kazuki Matuyama, Takao INAMURA, Hideki YANAOKA, Min ...
Article type: Article
Session ID: G0501-2-5
Published: September 12, 2009
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Air flow and spray produced from Rotary-bell cup atomizer were visualized using two-dimensional PIV method. Shaping air was supplied along the outside surface of the cup in order both to suppress the spray from radial spread of droplets due to centrifugal force and to enhance atomization. The efficiency of shaping air was investigated by using three shaping air nozzles of different geometry. The rotational speed of bell cup, shaping air flow rate and liquid flow rate were changed up to 35000rpm, 700NL/min and 300mL/min respectively. We observed that, with the increase of shaping air flow rate, a recirculation region was formed below the bell cup, and, over a critical shaping air flow rate, the atomization at the cup exit was enhanced.
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Eiji Yoshida, Takeshi Ueno, Shigehira Ozono
Article type: Article
Session ID: G0501-3-1
Published: September 12, 2009
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We tried to generate homogeneous turbulence of high intensity and large scale in a multi-fan wind tunnel. Because of independence of the fans of the multi-fan wind tunnel, we can arrange blowing and suction fans freely. In the present study, a fan driving mode of fractal arrangement was applied. We examined basic characteristics of generated turbulence.
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Yoichi YAMAGISHI, Shigeo KIMURA, Makoto OKI, Chisa HATAYAMA
Article type: Article
Session ID: G0501-3-2
Published: September 12, 2009
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It is known that for a square cylinder subjected to uniform flow, the drag force changes with the shape of corner cutoffs. To clarify the flow characteristics around a square cylinder with corner cutoffs we measured the drag coefficient for changing chamfer shape and dimensions. We analyzed the flow around a square cylinder with corner cutoffs by applying the RNG k-ε turbulent model, and investigated the surface flow pattern using visualization by means of the oil-film and mist flow method. From these results, we obtained the surface flow patterns by the oil-film method and numerical analysis. The drag coefficient of the square cylinder with 10% corner cutoffs was found to decrease by about 30 % compared with that for the square cylinder, since the wake area of this square cylinder was smaller compared with that of the other square cylinder.
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Motoki KAKIZAKI, Mikio TAKAHASHI, Hitoshi ISHIKAWA, Shunsuke YAMADA
Article type: Article
Session ID: G0501-3-3
Published: September 12, 2009
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The purpose of this study is to investigate the flow structure of a windbreak forest. Test specimens used in a wind tunnel experiment are two conifers which are evergreen with needle-shaped leaves. We measured the flow around a pair of living trees which have the distance of l=2d and 3d. Reynolds number based on U_∞. and the maximum crown width d of the living tree was 5.8×10^4. The mean streamwise velocity in the wake behind a pair of living trees was decreases more than that behind a single living tree. Moreover, the velocity defect in the case of the distance 2d between conifer A and conifer B is larger than that of in the case of the distance 3d.
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Eisuke UMEMURA, Satoshi KIKUCHI, Yasuaki KOZATO, Shigeki IMAO
Article type: Article
Session ID: G0501-3-4
Published: September 12, 2009
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The influence of the wing-tip plate on the wing in ground effect were examined by the wind tunnel experiment. The flow fields were measured by a particle image velocimetry, and the effect of the wing-tip plate on the wing-tip vortex and the aerodynamic characteristic was examined. The following results were given. The aerodynamic characteristic changed by the wing in ground effect was qualitatively same as past study results. Though only one wing-tip vortex exists near the wing-tip without the wing-tip plate, but, the two wing-tip vortices exist with the wing-tip plate. The wing-tip vortex with the wing-tip plate is away from the wing-tip compared with the case without the wing-tip plate.
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Eitaro KOYABU, Satoshi NAKAJIMA, Tsubasa OJI, Tetsuhiro TSUKIJI
Article type: Article
Session ID: G0501-3-5
Published: September 12, 2009
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The purpose of this study is to investigate experimentally how factors affect the transitional behavior of the boundary layer on the blade. This paper deals with the effect of Strouhal number. The flow fields on the blade change from an accelerating flow to a decelerating flow. Especially, there are few research examples about the effect of the periodic wake passing through the deceleration flow field on the blade. Then precise experiments are demanded by many researchers. Wake-affected boundary layer bypass transition was evaluated using a Hot-Wire Anemometer to get the ensemble-averaged velocity and intermittency factor from the raw velocity data under the influence of adverse Pressure Gradients.
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Minoru NAKATSUKA, Toshihiro TAKAMI, Kensuke TAKEDA, Shinichiro YANASE, ...
Article type: Article
Session ID: G0501-4-1
Published: September 12, 2009
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The flow through the curved pipe has been studied considerably, because of its practiced importance in mechanical engineering. This flow changes into the complex three-dimensioned flow which is formed the secondary flow by centrifuged force. The secondary flow is convenient for mixing fluid and promoting heat transfer, on the other hand it brings about the increase in the flow resistance. Therefore, it is necessary to investigate the relationship between fluid flow and the flow residence, for aiming to improve the performance of fluid instrument. In the present experiment, we introduced the Winglet in order to restrain the secondary flow in the curved pipe, and investigated the effect of the Winglet on the turbulent flow in the curved pipe. The experienced data showed that the asymmetry Winglet lead the decrease about 5 percents in the flow residence, because the secondary flow changed into the flow similar to the swirling flow and the bias of the mainstream disappeared. In conclusion, it was clear that the turbulent energy and wall shear stress are restrained.
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Koichi ARAGA, Yosuke NAKAMIZO, Shinnichi ITOGAWA, Keiji MURATA
Article type: Article
Session ID: G0501-4-3
Published: September 12, 2009
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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. This is 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 the heat transfer coefficients decrease during flow laminarization. The research objective is to examine heat transfer enhancement effects by air injection. This paper presents an experimental investigation on the heat transfer and flow characteristics in an air-surfactant solution two-phase flow through a vertical tube. The air was injected through the porous metal or the T-joint. In each air-inlet condition, heat transfer coefficients were enhanced drastically with the injection of air into a drag-reducing surfactant solution flow. In air injection through the porous metal, the flow pattern was bubbly flow which contains many micro-bubbles in any flow rate. As the enhancement rates of heat transfer coefficient, the air injection through a porous metal was more effective than a T-joint. This result means that the apparent concentration of rod-like micelles in a surfactant solution in micro-bubbly flow was more reduced than that in any other flow pattern.
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Hiroyasu OHTAKE, Hirotaka KUBO, Yasuo KOIZUMI
Article type: Article
Session ID: G0501-4-4
Published: September 12, 2009
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The pressure drop of water single-phase and argon-water two-phase flows in mini pipes and at sudden expansion and contraction (form losses) were investigated. Diameter of test section of mini pipes was 0.57, 0.4. 0.25 and 0.12 mm, respectively. The superficial gas velocity was 2.1 <U_g < 92.5 m/s, the superficial liquid velocity was 0.03 <U_1 < 10 m/s. The two-phase friction multiplier data for D > 0.5 mm showed to be in good agreement with the conventional correlations. On the other hand, the two-phase friction multiplier data for D <0.25 mm differed from the calculated values by the conventional correlations. New correlation of mini pipes was obtained for frictional pressure drop of gas-liquid two-phase flow. The coefficients of sudden expansion and sudden contraction in mini-pipes for the gas-water two-phase flow were proposed from the present experimental results. The experimental results were also examined through numerical simulation by a commercial code. New correlation of coefficients of form losses was obtained for gas-liquid two-phase flow.
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Hiroyasu Otake, Yasuo Koizumi, Yousuke Ehara
Article type: Article
Session ID: G0501-4-5
Published: September 12, 2009
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The pumping effectiveness of the micro T-junction with the oscillatory flow was examined. At one end of the top bar of T, there was a closed tank; Tank 1, that was solid with water. At another end of the top bar of T, there was a tank; Tank 2, that was open to the atmosphere. At the bottom end of the vertical branch of T, there was also a tank; Tank 3, that was open to the atmosphere. In Tank 2 and Tank 3, free surface of water was formed. The cross-sections of the flow path were 0.2 mm × 0.2 mm and 0.5 mm × 0.5 mm in the present experiments. Back-and-forth flow was created at the branch by a piezo actuator mounted at Tank 1. Water surface level in Tank 2 was higher than that in Tank 3. The water surface level height difference between Tank 2 and Tank 3 was mainly dominated by the back-and-forth velocity at the T-junction. The pumping performance from Tank 3 to Tank 2 started at the lower velocity in the smaller flow path.
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Tsubasa OHSHIMA, Hirotoshi YANAGI, Hiroyuki OHTSUKA, Koji MORINISHI
Article type: Article
Session ID: G0501-5-1
Published: September 12, 2009
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To establish the computational method of non-condensable gas bahavior in condenser; numerical simulation of gas/gas two- phase flow (vapor/non-condensable gas) was carried out using two-fluid model. The amount of condensation of vapor was decided by overall heat transfer coefficient and temperature difference between vapor and heat exchanger tubes. The change of outside tube heat transfer coefficient by non-condensable gas density were considered. The results obtained from the proposed model showed that there was stagnantation of non-condensable gas at the bottom region of tube bundle, and the effect of vent tube length on the efficiency of condenser was figured out.
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Masami SUZUKI
Article type: Article
Session ID: G0501-5-2
Published: September 12, 2009
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H-type of single-block grids is commonly used for blade cascades, because the grids can be simply generated However, the mt important iegion around a leading edge has large grid distoffion including a singular point Therefore, it is considered that sufficient calculation accuracy cannot be thtained. In this study the grids are arranged by a multi-block grid and an overset grid which are made of O-grid around a blade and H-grid between blades, because the distortion of H-grid is improved by using an O-grid arotmdablade. The three type topologies are compared ith the experimental results, and the differences of the characteristics are investigated The results of computational fluid dynamics are well in agreement with experimental results for three grid topologies, and even H-grid it became clear that the accuracy is practically sufficient
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Yuria OKAGAKI, Hitoshi SUGIYAMA, Naoto KATO
Article type: Article
Session ID: G0501-5-3
Published: September 12, 2009
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Numerical analysis has been performed for three-dimensional fully developed turbulent flow in a square duct with 45 degree ribs by using an algebraic Reynolds stress model. Calculated results of streamwise mean velocity and secondary flow vectors are compared with not only the experimental data but also the numerical data predicted by Reynolds stress model in order to examine the validity of the presented method. The compared results with the experimental and numerical data suggest that an algebraic Reynolds stress model is able to predict the characteristic features of mean velocity and has the potentiality to reproduce precisely the mean flow velocity as well as the Reynolds stress model.
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Terufumi IKEMOTO, Masayoshi OKAMOTO
Article type: Article
Session ID: G0501-5-4
Published: September 12, 2009
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The fully-developed compressible turbulent channel flows with the several Mach numbers are directly simulated and investigated. At the large Mach number case, the mean velocity shifts up from the logarithmic law and the density fluctuation is reinforced. Due to the compressible effect, the ejection event becomes active and the contribution of the large-scale motion in the streamwise direction increases in comparison with that of the incompressible flow.
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Masato HOTTA, Tomohiro FUKUI, Koji MORINISHI
Article type: Article
Session ID: G0501-5-5
Published: September 12, 2009
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Designing machine like a reciprocating compressor with a piston engine, it is necessary to consider various elements; for example, not only gas flows driven by piston, but also influence of valves on the flows. Tn such a simulation, it is difficult in generating grids to describe flows around the moving object. In this paper, the moving object is expressed by applying virtual flux method, and flows driven by the piston of reciprocating compressor were obtained. We compared the flows generated by two different computational domains and showed that vortical structures and pressure distribution depend on the difference of computational domains.
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Shigehiro HISANO, Tomohiro FUKUI, Koji MORINISHI
Article type: Article
Session ID: G0501-5-6
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Such as engines with driving pistons, it is important to understand gas flows in the cylinder to design more efficient intake and exhaust system. Above all, we have to consider the pressure distribution at near the spark plug caused by the shape of flow channel. In this paper, the numerical method of fluid-solid interactions for unsteady flow is used to demonstrate the gas flow driven by intake, compression, ignition and exhaust in the cylinder attributed to the motion of piston-crank system. As a result, the cell-motor torque contributes the piston-crank motion, consequently the compression phase is reproduced properly. In the future study, we try to consider other phases of the four-cycle engine for more detailed analysis.
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Shinki TANAKA, Nobuyuki YAMAGUCHI, Masayuki OGATA
Article type: Article
Session ID: G0501-6-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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A radial-vaned air-separator has demonstrated a significant stall improvement effect in axial flow fans. Changes in the internal flow patterns in the fan effected by the device were experimentally investigated. The air separator-applied condition turned out to create tip-peaky axial velocity distributions, compared with rather flat ones for the solid-wall conditions. It is understood that the inclined meridional streamlines have created higher Euler work and circumferentially uniform flow pattern, both of which tend to suppress fan stalling and occurrence of rotating stall phenomena. The effects have been achieved by a very small amount of recirculation flow within the air separator passage as small as 1% of the fan flow, for the practically important working flow range of the fan including the zone originally stalled for the solid wall condition.
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Koji SASA, Yutaka OHTA, Eisuke OUTA
Article type: Article
Session ID: G0501-6-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Unsteady flow structure between rotor blade-to-blade passages in a three-stage axial flow compressor is experimentally investigated by detailed measurements of wall pressure fluctuations, unsteady velocities and their wavelet analyses. The feature of the present tested compressor is a shock tube facility connected in series to the compressor outlet in order to apply a compression wave from the compressor downstream. Research attention is focused on the inception and post-stall transient characteristics of surge and rotating stall which occurs simultaneously. The unsteady behavior of the compressor operating point on the performance curve under surging may largely depends on the stall configuration of the compressor blade rows. The unsteady flow filed under coexistence system of surge and rotating stall are also discussed.
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Masahiko SAKAMOTO
Article type: Article
Session ID: G0501-6-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The purpose of this study is to examine the characteristic of the pressure pulsation in a centrifugal blower pipe line with the discharge opening below the water surface. The effect of the piping system on the pressure pulsation was studied experimentally. The pressure and the flow rate in the pipe line were measured for various parameters such as the depth of the discharge opening and the number of revolution for the blower. The conclusions are as follows. The dominant frequency obtained by the experiment agrees qualitatively with that obtained by the modified Helmholtz frequency involving the volume of the exhaust duct as the depth of the discharge opening is deep. The fluctuation of the air-water interface becomes the oscillation resource, and the shape of the pipe line at the discharge opening affects the characteristics of the pressure pulsation.
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Takashi GOTO, Eri OHMOTO, Yutaka OHTA, Eisuke OUTA
Article type: Article
Session ID: G0501-6-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The effects of behavior of leading-edge vortex, which exists on the suction surface of the diffuser vane, on flow fields in centrifugal compressor are discussed by experiments and CFD technique. The focus of the research is to investigate the behavior of the leading-edge vortex at low-flow rate operation. The leading-edge vortex becomes large by about 80% of diffuser width under the low-flow rate conditions. According to numerical analysis, the internal flow in the diffuser passages is complicated with bubble type vortex break down of the leading-edge vortex, and the main stream in diffuser passages is blocked by the vortex. Therefore, the vortex is considered to cause a loss of diffuser passages of the centrifugal compressor. Furthermore, diffuser stall is considered to develop due to the leading-edge vortex pushed upstream to the impeller direction.
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Yuuichi MOMOSAKI, Naoto Ozaki
Article type: Article
Session ID: G0501-6-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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In this research, we carried out a numerical simulation of stirred fluid by rotating gear using MPS method. MPS (Moving Particle Semi-implicit) method is one of the mesh-free particle methods. The particle method has used an effective technique to treat a free surface flow such as dam breaking or splash. Usually, the particle methods use particles for structure expression as well as fluid, but we used a polygon model on the boundary to improve the accuracy of interaction between fluid particle and structure surface. As a result, we could make a prediction of stirring-resistance value in good agreement with experimental measurement, and yielded a stress distribution by viscous fluid on the polygon surface.
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Masanori TSUTSUMI, Yukio UMEZAKI
Article type: Article
Session ID: G0501-6-6
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Recently, fully three dimensional design method is applied to the blades of almost stages in the steam turbine. However, detailed mechanism of three dimensional effects on the flow within a turbine cascade has not been clear completely in spite of many studies for a long time. Therefore, turbine designer has to pay careful attention to the blade stacking using the blade leaning technology. In order to blush up the fully three dimensional design method, the authors have reviewed the complicated flow pattern within a bowed blade in detail through the cascade testing and CFD, and have proposed a new idea to improve conventional bowed blade. In conclusion, the reason for increasing in profile loss at mid span and decreasing in secondary loss near the endwall of conventional bowed blade has been explained, and a effect of the throat expansion at mid span as a new technology on reducing the losses in the bowed blade has been verified by experiment.
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Satoshi OGATA, Hiroshi SHINTANI
Article type: Article
Session ID: S0501-1-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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To clarify the effects of surfactant solutions on the drag coefficient of a circular cylinder, the flow past a circular cylinder was investigated at 0.6 <Re <20 by measuring the drag and by visualizing the flow. The diameters of test cylinder were 2 and 5 mm. Surfactant solutions were aqueous solutions of oleyl-methyldihydroxyethyl ammonium chloride in the concentration range of 200 to 500 ppm with sodium salicylate. It was clarified that the drag coefficient of the circular cylinder in surfactant solutions increases comparing that in tap water. The inception Reynolds number of the drag increase was also clarified. The flow visualization results showed that the drag of surfactant solutions increases because of the existence of the wide stagnant zone around the cylinder. The drag coefficient of the circular cylinder in surfactant solutions was dependent principally on the parameter U/d (=mean velocity/cylinder diameter).
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Takashi Koshiba, Takehiro Yamamoto
Article type: Article
Session ID: S0501-1-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The purpose of this study is to observe the unstable flow seen on the cone circumference in the measurement of shear property for the surfactant solutions with a cone-plate type of Rheometer. The surfactant solutions used for the experiment are six kinds of CTAB/NaSal solutions having different NaSal concentrations. In the visualization results at circumference of cone, the instability of liquid surface notably appeared in the fluids with low NaSal concentration, and it was considered that the property of shear flow at higher shear rate was closely related to the unstable flow. Furthermore, the value of critical shear rate at which flow instability appears decreases with the increment of relaxation time of surfactant solutions. Therefore, the correlation between both results suggested the existence of elasticity induced by the structural change of micelles.
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Kazuhiro SAWA, Takehiro YAMAMOTO
Article type: Article
Session ID: S0501-1-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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In wormlike micelle solutions with hydrophobic salt (CTABINaSaI), micelles tangle each other and the solutions show remarkable viscoelasticity. Its flow property complexly changes with flow conditions because the network of wormlike micelle is affected by the flow. In our research, we analyzed the gapwise velocity profile of the sample in shear flow to clarify their flow properties. We also measured temporal velocity change and flow birefringence to analyze the relation between the velocity profile and the orientation of micelle. The velocity profile had two or three infection points around which the velocity gradient rapidly changed, that is shear-banding. In the end of shear-thinning regime in a flow curve, temporal changes in both velocity and birefringence have nearly equal periodical time. The experimental results show that they are strongly connected.
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Atsushi YAMASHITA, Takehiro YAMAMOTO
Article type: Article
Session ID: S0501-1-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The flows of CTAB/NaSal solutions in two rectangular channels were investigated. Measurments of flow property, velocity profile and flow birefringence and flow visualization experiments were carried out. The solutions show both shear-thinning and shear-thickening in viscosity. In the shear-thinning region, flow birefringence starts to increase. In the shear-thickening region, the magnitude of flow bireflingence is larger than that in shear-thinning region and a striped white turbidity emerges at near-wall region where the velocity gradient is large. Moreover, white turbidity periodically repeats appearance and disappearance in a small channel, while it continues to appear in a large channel. These results indicate that a large flow space is one of the requirements of stable emergency of white turbidity.
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Tsutomu TAKAHASHI, Yuuji AOYAMA, Masataka SHIRAKASHI
Article type: Article
Session ID: S0501-1-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Occurrence of the shear-induced structure change of wormlike micelles solution on restarted step shear flow with interval time was investigated. An aqueous solution of CTAB/NaSal was used as a test fluid and it is known that it exhibits one-mode Maxwell type viscoelastisity and also cause flow-induced structure change by shear. The step shear flow with certain shear rate is applied and suddenly stopped. With certain interval time, the second step flow with the same shear rate is applied. On the restarted flow, the shear stress is strongly affected by the interval time but the birefringence is not affected when SIS is caused. The orientation of the micelles is quickly recovered but the SIS needs large energy for restructuring.
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Hideya NISHIYAMA, Hidemasa TAKANA, Kotoe MIZUKI, Keisuke SHINOHARA, Ka ...
Article type: Article
Session ID: S0501-2-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Magneto-rheological fluid (MR fluid) is one of the functional fluids which responds to the magnetic field and exhibits a semi-rigid behavior even under a small magnetic field strength. Then, MR fluid plugging performance by aggregation of magnetized particles in MRF is recently expected to be one of the most promising applications to medical or safety devices, such as blood flow control or steam shut-down valve. In this study, dynamic response of MRF plugging in pressure mode with fluid/wall interactions was experimentally investigated, considering the effects of applied magnetic flux density, piston head velocity, wall surface structure and elasticity of biological tube. The final objective of this study is to provide the fundamental data for the novel applications of MR plugging performance to medical or safety devices for flow control.
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Alfeus SUNARSO, Tomohiro TSUJI, Shigeomi CHONO
Article type: Article
Session ID: S0501-2-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Molecular dynamics simulations of backflow in nematic liquid crystals confined between a parallel plates cell was performed, and the effects of electric field strength and temperature were investigated. Under the application of electric fields, transient velocity fields are generated as the result of molecular reorientation. The magnitude of velocities and the time required for the development of the velocity fields depend on the strength of electric fields and temperature. With the increase in electric field strength, the magnitude of velocity increases and the time to reach the maximum velocity becomes shorter. With the increase in temperature, the kinetic energy of molecules becomes more dominant than the potential energy such that the resistant to the bulk reorientation by the electric field becomes smaller. As the consequence, under the same electric field strength, the magnitude of velocity increases and the time to reach maximum velocity decreases with the increase in temperature.
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Takema NAKAZAWA, Takanori MATSUMI, Tomohiro TSUJI, Shigeomi CHONO
Article type: Article
Session ID: S0501-2-3
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The effects of the duty and the frequency of the applied pulsed voltage on the driving performance of liquid crystalline micro-actuators are experimentally analyzed. The liquid crystalline material 4-cyano-4'-n-pentylbiphenyl is placed between two parallel glass plates, and the pulsed voltage is applied between the glass plates. The upper glass plate is moved by the electric field induced liquid crystalline flow when the plate is not fixed. The movement of the upper glass plate is observed under microscope. From the experimental result, it is found that the moving speed of the upper glass plate strongly depends on the frequency, and shows the maximum for the duty ratio 10% and the frequency 300Hz.
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Yasuhiro ABE, Takatsune NARUMI, Tomiichi HASEGAWA, Mayumi OUCHI
Article type: Article
Session ID: S0501-2-4
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Flow behaviors of polymer solution in oscillatory flow have been investigated with a micro abrupt contraction channel. Fluorescently-stained DNA polymer solutions have been utilized to observe the flow patterns with fluorescent microscope. In conversing flow periods in the micro oscillatory flow, corner vortexes were generated and grew to a maximum size, but no separation or no vortex was observed in diverging flow period. In the cases of large amplitude oscillatory flow, the vortexes were generated in the first half accelerating flow from flow reversal and grew even in the later half decelerating flow. When the amplitude was small, the vortexes were generated in the latter decelerating flow. It is considered that these results meant vortex generation was affected not only instantaneous condition but also flow history. The maximum size of the vortexes was comparable to the amplitude of the oscillatory flow.
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Makoto TAKASHIMA, Mayumi OUCHI, Takatsune NARUMI, Tomiichi HASEGAWA, T ...
Article type: Article
Session ID: S0501-2-5
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Structural relaxation process of DNA molecules after the cessation of micro Couette flow with 5-l0iim gap were investigated with fluorescent microscopy. In order to clarify the influence of entanglement of molecules to the relaxation behavior, we have tested dilute labeled T4-DNA solution and semi-dilute solutions with mixture of a small amount of the labeled T4-DNA and unlabeled ones. Moreover, viscosity of the dilute solution was closed to that of the semi-dilute one with sucrose. It was clarified that the relaxation process was affected with the gap size in the micro system and the smaller gap delayed the structural relaxation. Even if the solutions have same viscosity in macro sense, the entangled system showed longer relaxation times than those of dilute system.
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Kazunori YASUDA, Kunji CHIBA, Yukiharu IWAMOTO, Motosuke SOGO
Article type: Article
Session ID: S0501-2-6
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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Secondary vortex enhancement was examined for fiber suspension flows containing bacteria cellulose fiber (BCF) at weight fractions from 0.07 to 0.28 wt%. BCFs were derived from nata de coco. These fluids have non-Newtonian properties even at low weight fraction of BCF. The channel used has a rectangular cross section and an abrupt contraction geometry. As a result, we found that the vortex becomes large as increasing flow rate for BCF suspensions, whereas it becomes small for a Newtonian fluid. The vortex size enhancement is probably caused by the increment of elongational viscosity of test fluid.
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Hiroshi Mizunuma, Yukihiro Michiwaki
Article type: Article
Session ID: S0501-3-1
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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The measurements of MRI movies were repeatedly taken for a pharynx and a larynx. From the obtained database of the MRI slice images, the swallowing movement was expressed as a function of 4D-space (x, y, z, t). Since the resolution of MRI is insufficient, we cannot detect the fast movement of an epiglottis and the ambiguous border of a bolus. Thus, the shape of the epiglottis was determined from CT-images, and VF-images were analyzed to integrate its motion into the 4D swallowing movement. The bolus was initially assumed to fill the pharynx, and the following bolus flow was analyzed.
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Shuhei FUJIMOTO, Yuichi MURAI, Yuji TASAKA, Ichiro KUMAGAI, Yasushi TA ...
Article type: Article
Session ID: S0501-3-2
Published: September 12, 2009
Released on J-STAGE: August 01, 2017
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We report a little-known deformation phenomenon occurring at the interface between two immiscible liquids. The two liquids are in a cylindrical container and set into motion by a rotating lid positioned above the interface. The upper liquid is about 100 times viscous than the lower and a difference in density between the liquids is about 3.5 %. Depending on the rotational speed of the lid (Ω), the topology of the interface changes drastically: from low Ω to high Ω, a simple hump, a cusp shape, a shape like Mt. Fuji, and a shape like a bell appears in sequence.
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