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Published: September 15, 2006
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Article type: Index
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A1-A7
Published: September 15, 2006
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Teruo KUMAGAI
Article type: Article
Session ID: 2214
Published: September 15, 2006
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This paper describes the isotropic tensor of rank 4 in three-dimensional space using polyadic algebra. The isotropic tensor of rank 4 appears in the relation between strain and stress for the well-known Navier-Stokes equation. When the deformation of viscous fluid is assumed to be slight and isotropic, the isotropic tensor of rank 4, that is Cijkl, is reconfirmed explicitely to be described as C_<ijkl>=Aδ_<ij>δ_<kl>+Bδ_<ik>δ_<jl>+Cδ_<il>δ_<jk>, where δ denotes the Kronecker delta. A, B and C denote the constants due to fiuid properties. In this case the polyadics is newly found to be suitable for the description of the rotation of the orthogonal curvilinear coordinates. The polyadics may be useful to describe the fluid properties further for microhydrodynamics and non-Newtonian fluid flow.
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Masashi YAMAKAWA, Kenichi MATSUNO
Article type: Article
Session ID: 2215
Published: September 15, 2006
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Moving-boundary problems are dealt with in a lot of scientific research and engineering field. In the case using body-fitted coordinate system for these problems, it is important to calculate that moving-gird would not affect to flow field. Although limited for two-dimensional system, we have already proposed the unstructured moving-grid finite-volume method. The feature of this method is volume integrating for space-time unified domain, and the method is able to satisfy the geometric conservation lows. In this paper the method is developed to three-dimensional system for three-dimensional moving-boundary problem.
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Kazutoyo YAMADA, Ken-ichi FUNAZAKI
Article type: Article
Session ID: 2216
Published: September 15, 2006
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The present work is an attempt to accelerate the convergence to steady flow solution in the lattice Boltzmann method (LBM). The discrete Boltzmann equation, which had an additional term to avoid the relaxation time from getting too small, was solved implicitly to use a large time step. The proposed method was validated for the cavity flow. The convergence rate was markedly enhanced compared to that of the standard LBM. The present method was also tested for the cylinder flow to investigate its applicability for the unsteady flow. The result of the present method was in good agreement with the experiment.
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Takahiro WATANABE, Masaya SHIGETA, Seiichiro Izawa, Yu FUKUISHI
Article type: Article
Session ID: 2217
Published: September 15, 2006
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Double-diffusive finger convection known as salt finger is simulated by the SPH method. The algorithms for the temperature and salinity diffusions are added to the SPH method extended for the incompressible flow computation. It is shown that the growth of salt finger can be simulated by SPH.
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Kei AKASAKA, Kenji ONO
Article type: Article
Session ID: 2218
Published: September 15, 2006
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Voxel based simulation is very convenient at the early stages of a product design because the simple block approximation of a shape can realize automatic and robust mesh generation. However, the voxel method is not capable of simulating the characteristics of flow and expressing the detail shapes less than the voxel size. Therefore, the relationship based on an experimental data, which reflects the flow characteristics, is often incorporated into the simulation as boundary conditions. For accurate flow simulation in an engine bay, the satic pressure drop caused by heat exchanger should be taken into account in governing equations. In this paper, the modeling of pressure loss at the heat exchanger on the voxel method is proposed. Incompressible flow around a heat exchanger was calculated using the present method as verification. It was found that the proposed method could accurately predict the pressure drop and flow field.
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Shinsuke MATSUNO, Susumu TOKURA, Yoshiyuki ISO, Hiroyuki UCHIDA, Toshi ...
Article type: Article
Session ID: 2219
Published: September 15, 2006
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A numerical model of Joule-heated glass melters for high-level waste vitrification has been developed to assist its operations. Electric Field, heat transfer and fluid dynamics are coupled in the simulation because they strongly affect each other. The results indicate that electric field at the bottom is formed asymmetrically during heating phase because of the arrangement of the electrodes. Temperature distribution at the bottom, however, is kept almost symmetrically due to mixing effect by natural convection of the glass.
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Yoshiyuki ISO, Shinsuke MATSUNO, Hiroyuki UCHIDA, Susumu TOKURA, Toshi ...
Article type: Article
Session ID: 2220
Published: September 15, 2006
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We have developed a numerical simulation scheme which couples electric field, heat transfer, fluid dynamics and metal particles behavior in a joule-heated glass melter. The particles behavior is treated as the continuous transport of the particle concentration by the Eulerian method. It is able to evaluate the unsteady operational melter status and performance, which are strongly affected by the settling and deposition of the platinum group metals included in high level waste. Numerical simulation showed that high current density bypasses along the inclined bottom wall due to the increase of the electrical conductivity in the deposited layer of the metals. As for remaining mass of the metals in the melter, numerical results agreed reasonably well with the experimental data.
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Hideya NISHIYAMA, Hidemasa TAKANA, Kazunari KATAGIRI, Masaaki MOTOZAWA ...
Article type: Article
Session ID: 2301
Published: September 15, 2006
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Experimental analysis on the cluster formation of MR fluid and rheological properties under the magnetic field are carried out. Through the measurement of ultrasonic propagation velocity in MR fluid, the cluster behavior in pressure-driven flow is clarified in detail. Finally, the flow control characteristics of MR fluid in a rectangular channel are evaluated to provide the fundamental data for the design of the advanced MR valve system.
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Masaaki MOTOZAWA, Yoshiyuki MATSUMOTO, Tatsuo SAWADA
Article type: Article
Session ID: 2302
Published: September 15, 2006
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The properties of ultrasonic propagation velocity in water-based and kerosene-based magnetic fluids and an MR fluid are examined experimentally. The ultrasonic measurement scheme is based on the pulse method. The external magnetic field intensity is varied from 0mT to 550mT and the angle between the magnetic field direction and the direction of ultrasonic wave propagation is adjusted from 0°to 90°. The ultrasonic propagation velocity changes with the elapsed time of external magnetic field application and with magnetic field intensity. Moreover, the ultrasonic propagation velocity in MR fluid is larger than that in magnetic fluids. These properties of ultrasonic propagation seem to be highly influenced by the formation of chain-like clusters (in the magnetic fluids) and robust clusters (in the MR fluid).
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Seiichi SUDO, Yuichi KUROSU, Tetsuya YANO, Hirokatsu HONMA
Article type: Article
Session ID: 2303
Published: September 15, 2006
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This paper describes the dynamic response of a small magnet encompassed with magnetic fluid in the external alternating magnetic fields. This study is concerned with the development of the micro magnetic fluid actuator composed of a permanent NdFeB magnet and kerosene-based magnetic fluid. The actuator is characterized by wireless operation with alternating magnetic field. The driving characteristics of small permanent magnet encompassed with magnetic fluid are examined by using a digital high speed video camera system. Experimental results show the possibility of the control of the permanent magnet motion by the external magnetic field.
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Kunio SHIMADA, Yongbo Wu, Yoshio Matsuo
Article type: Article
Session ID: 2304
Published: September 15, 2006
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As a new intelligent fluid, we have proposed a magnetic compound fluid (MCF). This fluid has nm-sized magnetite and μm-sized iron particles in a solvent. In this report, we clarified the polishing mechanism on MCF float polishing. The MCF polishing is fine finishing with nm-order surface roughness and has a large clearance between the polishing tool and the polished specimen. These causes are due to the magnetic clusters in the MCF, the buffer material of α-cellulose and the abrasive particles involved in the clusters.
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Ryosuke IBATA, Jyun KENMOTSU, Hiromichi OBARA, Yasuaki MATSUDAIRA
Article type: Article
Session ID: 2305
Published: September 15, 2006
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Diamond particle dispersion type functional fluid impressed high AC voltage forms the rotational flow structure under the high electric intensity and the low frequency conditions. This study investigated fundamental flow characteristics of the rotational flow structure to improve a new polishing technique for nano-microscopic processing technology and to develop novel micro devices. This structure consisted of rotational flows generated with positive and negative acceleration flows at even interval in plane. The acceleration flow was induced near the electrode by alternate electric field and it was drastically developed and arrived at the opposite side of the electrode. This flow had a certain delay from electric field excitation of the rectangular AC wave and this delay occurred independently of the impressed frequency of the electric field.
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Masami NAKANO, Shuhei YAMAMURA, Ryosuke KETA, Katsufumi TANAKA
Article type: Article
Session ID: 2306
Published: September 15, 2006
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The transient response of induced shear stress and the related flow behavior of an ER suspension containing nano-sized TiO2 particles have been investigated when it has been under the simultaneous stimulus of a constant DC or AC electric field and shear using a parallel rotary disk rheometer. As the DC electric field strength increases, the particles in the ER suspension form lamellar formations in the direction of shear, and sometimes agglomerate to form a non-uniform disturbed flow pattern inducing the violent fluctuation of the shear stress as time passes. As a result, the shear stress under DC electric field changes consistently with the morphology of the particle formations. While, the ER suspension under AC electric field (1kHz) is very stable to keep an almost constant shear stress, showing almost no morphology changes. The effects of shearing time, electric field strength, gap height between disk electrodes on the shear stress and the flow morphology are investigated experimentally.
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Kazunori HAYAKAWA, Tetsuhiro TSUKIJI
Article type: Article
Session ID: 2307
Published: September 15, 2006
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A micro-motor using functional fluid with the electrodes on the bottom surface of the mini-cylinder is produced experimentally. A rotor in this micro-motor in the functional fluid rotates by the rotation of the functional fluid, when the unsteady electric fields are added on the electrodes. The micro-motor is 5mm in length and 4mm in inner diameter. To rotate the rotor, three kinds of liquid crystals and a flourinert were injected in the micro-motor. The amplitude of the voltages and the shape of the electrodes are changed to investigate the effect of the unsteady electric fields on the rotational speed of the micro-motor.
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Takanori MATSUMI, Tomohiro TSUJI, Shigeomi CHONO
Article type: Article
Session ID: 2308
Published: September 15, 2006
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The experimental investigation on the controlling of operation direction of a liquid crystalline actuator with orientation layer patterning has been achieved. Opposite rubbing treatment are given at the left and right side of the glass plates. When the electric field is imposed on the left (right) side of the liquid crystal cell, the liquid crystalline flow toward the right (left) side of the liquid crystal cell is induced. The movement of a particle mixed in the liquid crystal is successfully controlled by imposition of the electric pulse on the left or right side of the cell.
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Jun Fukada, Takatsune Narumi, Tomiichi Hasegawa, Satoru Kiryu
Article type: Article
Session ID: 2309
Published: September 15, 2006
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The instability of flow induced structure of liquid crystalline polymer solution has been investigated in two dimensional channel flows. The influence of round off curvature at a corner on the unstable behavior after a flow direction change has been mainly examined. The orientation angle and the dichroism were measured with a laser optical measurement system. The unstable behavior of liquid crystalline polymer solution has typical periodic oscillatory characteristics, and the periodic motion became larger toward the downstream from the corner. The increase in periodicity was significant at the inner side of the channel. The larger round off of the corner suppressed the periodic motion, so that it is considered that the shape of the corner is one of the causes of the instability.
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Kazunori YASUDA, Norihiro OHARA, Mitsuru MUGURUMA, Noriyasu MORI
Article type: Article
Session ID: 2310
Published: September 15, 2006
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Velocity profiles in concentrated particle suspension flows through a channel were measured using magnetic resonance imaging (MRI). We used non-Newtonian fluids containing suspended particles at high volume fractions. The particles have spherical, slender, and disk-like shapes, respectively. These suspension fluids are opaque. The channel used has a square cross section and an abrupt contraction geometry. As a result, we found that the velocity profile depends on the particle shape in the contraction. Spheres did not affect the flow field but slender and disk-like particles caused a concave shape in the velocity profile.
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Hideaki KURIHARA, Masaharu KAMEDA, Mie ICHIHARA
Article type: Article
Session ID: 2311
Published: September 15, 2006
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Fragmentation criterion is closely related to magma rheology. To reveal the relationship, we carried out laboratory experiments on magma fragmentation with analogous materials. Commercial syrup was used as an analogous material of magma. A pressure-vacuum chamber was used to apply rapid decompression on the materials. The initial pressure was varied from 2 MPa to 3 MPa. The gas-volume fraction of the syrup under pressure was fixed as 2% or 6%. The viscosity varied from 5×10^5 Pa・s to 5×10^7 Pa・s. The experimental results indicate that fragmentation process is classified with viscosity. The fragmentation is observed when the pressure drop reaches critical value within the order of relaxation time of syrup. In addition, this constraint on the decompression time is relaxed as the initial void fraction or initial pressure increases. This implies that the energy stored in the bubbles is a dominant parameter to characterize the fragmentation.
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Hitoshi FUJII, Yutaka ABE, Nobuyuki WAKABAYASHI
Article type: Article
Session ID: 2312
Published: September 15, 2006
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The volcanic eruption occurs due to the sudden decompression of the high-pressure high-temperature high-viscosity magma. It is mainly depended on the appearance of the gas phase in the magma whether it is an explosive eruption or not. In the present study, the volcanic eruption is reproduced with the high-pressure visible shock tube apparatus and simulant materials. The simulant materials for the magma are two-fluid component of silicone oil as high viscosity fluid and acetone as volatile substance. In the experiment, the bubble forming behavior of the simulant materials and the rapid change in pressure is observed. Bubble forming behavior had completed in very short span and then bubbles developed. The number of bubbles that generated under sudden decompression increased as the initial pressure increased. It is indicated from the experimental results that the driving force of bubble forming under sudden decompression depends on the initial pressure.
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Kazuyuki TAKASE, Hiroyuki YOSHIDA, Hidesada TAMAI, Yasuo OSE, Takayuki ...
Article type: Article
Session ID: 2313
Published: September 15, 2006
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Three-dimensional large-scale numerical simulations were carried out to predict the complicated water-vapor two-phase flow characteristics in a fuel bundle of an advanced light water reactor. Conventional analysis methods with a two-fluid model need composition equations and empirical correlations based on the experimental data. Therefore, it is difficult to obtain high prediction accuracy when experimental data are nothing. Then, a new two-phase flow analysis method was proposed and the TPFIT code was developed. This paper describes the predicted liquid film, bubbly and droplet flow behavior in the simulated fuel channels with the TPFIT code, and the predicted two-phase flow behavior around a curved fuel rod with the FLUENT code which is one of the most famous commercial code. From the present results, the high prospect was acquired on the possibility of development of the thermal design procedure of the advanced nuclear reactors by large-scale simulations.
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Tomoaki ITANO, Takeshi AKINAGA, Masako SEKI(SUGIHARA)
Article type: Article
Session ID: 2314
Published: September 15, 2006
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Using the method of molecular dynamics, we numerically examine the pressure difference between ideal solution and pure solvent separated by a semi-permeable membrane in the equilibrium state, which is normally termed osmotic pressure. The virial theorem in the system is derived to measure pressures in the ideal solution and the pure solvent, then the validity of van't Hoff law is confirmed up to moderate concentration of the solution.
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Shuichi IWATA, Shingo UCHIDA, Kazuto ISHIDA, Hideki MORI
Article type: Article
Session ID: 2315
Published: September 15, 2006
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A local shear rate due to a local flow occurred surrounding a small bubble under a periodical oscillating pressure field was derived theoretically, which is able to estimate an enhancement in removing speed of the bubble from shear-thinning fluids. This estimation requires experimental data of changing bubble size over a cyclic period. Because the oscillation frequency was too high to record by video camera, we use a special technique. The pressure inside a closed test cell was controlled by vibrating a thin-film set on the cell. We compared the observed rising velocities under pressure oscillating condition with a velocity that was estimated from the shear viscosity and mean bubble size, which is measured by the special technique. We concluded that the shear-thinning behaviour of the fluid due to the local shear flow in the vicinity of the bubble under periodical oscillating pressure enhances rising velocity itself.
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Kayo YOKOYAMA, Hiroshi YAMAGUCHI
Article type: Article
Session ID: 2316
Published: September 15, 2006
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This report describes a swirling flow in rotating pipe section with viscoelastic fluid containing micro-bubbles. Particular attention was given to verify the flow behavior and its associated bubble motion in a viscoelastic fluid, when the dispersed micro-bubble flow is entered from a stationary pipe to the rotating pipe section. The result showed that elongated circulation vortex zones were generated, similar to Newtonian case. From experimental results, and an aid of the numerical simulation, the stagnation point moves towards the inlet region as swirl ratio Ω is increase. It was also found that the stagnation point further moves toward the inlet in the case of viscoelastic field, showing that the dependence on Re^* becomes infinitesimal. In the bubble behavior, it was shown that the big bubble fell to the stagnation point, and that the parabolic surface is formed by some smaller bubbles which are caught in orbits of the rotating flow field.
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Hiroshi YAMAGUCHI, Tomoko MATSUMOTO
Article type: Article
Session ID: 2317
Published: September 15, 2006
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Using circular manifold distributing channel, the flow transition phenomena of viscoelastic fluid are investigated particularly. In the present study, the objective is to clarify the transition phenomena of three-dimensional flow patterns with different Reynolds numbers at laminar. Flow transition and changes of the mode are determined by direct observations with the flow visualization at the expanded part. It was found, that there are asymmetric three-dimensional flow fields by the effect of swirl flow in both Newtonian and viscoelastic flows. It was observed that the structure of a secondary flow near the outlet pipes is highly asymmetric. It is further known that the secondary flow became smaller as Reynolds number is increased.
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Takuya OSAWA, Hiroshi MIZUNUMA
Article type: Article
Session ID: 2318
Published: September 15, 2006
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In the extrusion processing of the polymer melt, the extrudate often suffers melt fracture, which is classified into "sharkskin", "spiral fracture", or "wavy fracture" depending on the surface roughness. The mechanism of "sharkskin" was proposed here based on the microscopic observation at the slit exit. The polymer was linear Polydimethylsiloxane (PDMS). The visualized results showed that "sharkskin" occurs because of the adhesion/cohesion failure at the die inside, or the adhesion of the polymer to the die exit edge side. In addition, in order to suppress "sharkskin", the flow of the slit exit was controlled using air jet and a protruded edge, and their influence on the exit flow was investigated.
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Kazunori SORIMACHI, Tomiichi HASEGAWA, Takatsune NARUMI
Article type: Article
Session ID: 2319
Published: September 15, 2006
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When air pushes a more viscous fluid in two parallel plates by a syringe pump, viscous fingering pattern have been observed. Water and aqueous glycerin solutions are used as Newtonian fluids. Polyacrylamide (Separan AP30) solutions and aqueous glycerin solutions adding polyacrylamide are used as non-Newtonian fluids. It was found that it showed the bifurcation of viscous fingering to be different by a kind of solution. And, it was found that the solution concentration, gap and air pressure influenced a bifurcation pattern. Furthermore, it was not found a large bifurcation pattern in dilute Polymer solution and aqueous glycerin solutions with lower concentration. Then, tip speed of bifurcation was low.
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Makoto Okawara, Tomiichi Hasegawa, Takatune Narumi
Article type: Article
Session ID: 2320
Published: September 15, 2006
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It has been reported that even water known as Newtonian fluid shows a peculiar behavior in flows through a fine gap or pores [1]. This peculiar behavior is not made clear but should be investigated from many aspects not only for academic field but also for industries. In this study, we make so-called Newtonian fluids to flow through a two-dimensional slot and examine it by the rheo-optical technique: Mach-Zehnder interferometer is used and interference fringes are observed around the slot gap by record with a digital video camera. Ion Exchange Water, Silicone oil were used as test fluids. As a result, we obtained peculiar phenomenon in interference fringes which can not be explained by temperature change.
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Takamasa HASHIMOTO, Koki MORI, Takehiro YAMAMOTO
Article type: Article
Session ID: 2321
Published: September 15, 2006
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Worm-like micelles entangle and form networks like polymeric fluids. In the present study surfactant solutions system of CTAB/NaSal were used to examine the flow property with a stress-controlled cone-and-plate rheometer and carry out the creep test. At relatively low salt concentrations, the dependence of the shear rate on time was observed on creep test and it took a very long time to converge on constant shear rate. Flow property obtained from the creep test apparently exhibited shear-rate-jump after shear-thinning was observed. It is thought that this phenomenon was related with the structural change of micellar networks. On the other hand, at relatively high salt concentrations, the shear rate kept constant in shorter time after start-up. The shear-rate-jump was not observed.
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Tsuneo AZUMA, Koichi ARAGA
Article type: Article
Session ID: 2322
Published: September 15, 2006
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This paper describes the effect of drag reducing surfactant (C_<14>TABr) additives on the laminar-turbulent transition in pipe flow. The experiment was carried out using the glass tube of 5.02mm in diameter and 2712mm in length. The transition process depending on the surfactant concentration was observed by means of high-speed video photography. Within the Reynolds number ranging from 2000 to 3000, a temporary rapid increase in the friction factor appeared although the flow was quasi-laminar. In a surfactant concentration that exceeds 230 ppm, a turbulent transition happened gradually and vaguely, not drastically as the Reynolds number increased.
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Kenichiro MATSUO, Hiroki TAWARA, Mizue MUNEKATA, Hiroyuki YOSHIKAWA, H ...
Article type: Article
Session ID: 2323
Published: September 15, 2006
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The purpose of this study is to investigate the effect of rheologic characteristics of surfactant solution on the swirling flow characteristics. The drag-reducing rate in a swirling pipe flow was estimated by the pressure drop and the velocity profiles were measured by LDV. The non-Newtonian viscosity and the relaxation time were measured by a rotation viscometer. It is shown that the drag-reducing rate depends on the relaxation time strongly, compared with the rheologic parameters by a power law. The effect of apparent viscosity on the swirl intensity and the stronger effects of relaxation time on the decay of swirl intensity are shown also and discussed.
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Hiroki OKADA, Mamoru TANAHASHI, Toshio MIYAUCHI
Article type: Article
Session ID: 2324
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The characteristics of heat transfer and drag reduction of turbulent water flow with surfactant have been investigated based on the coherent fine scale eddy in near-wall turbulence. To analyze the heat transfer and drag reduction, time scale ratio of surfactant to coherent fine scale eddy has been introduced. This time scale ratio characterizes the range of drag and heat transfer reduction, simultaneously. As the fluid near the wall is cooled in the heat exchanging process, the drag reduction range is shrunk for the high temperature conditions. Therefore, decrease of the heat transfer can be prevented in heat exchangers.
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Yukiharu IWAMOTO, Hideki HIBARA, Motosuke Sogo
Article type: Article
Session ID: 2325
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Reynolds shear stress of surfactant solution flowing in a circular pipe was investigated experimentally by means of Laser Doppler anemometery. Concentrations of surfactant solution were 0, 28, 50, 100 ppm, and Reynolds numbers based on a bulk velocity, viscosity of water and a pipe diameter were set to 20000, 40000, 60000. Results show that the extreme suppression of Reynolds shear stress compared to water was occurred in the case of surfactant solution, and this was achieved by counteractions between outward interaction and ejection, inward interaction and sweep, respectively. The shear viscosity calculated from mean velocity distribution and previous results of rheometer test shows that there is a low viscosity region below the region which is in a shear induced state. This region makes a difference in streamwise velocity fluctuation between the cases of upward and downward fluid motion.
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Keizo WATANABE, Satoshi OGATA
Article type: Article
Session ID: 2326
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We are studying drag-reducing biopolymers produced by malted rice. In this work, the turbulent drag reduction of a circular pipe flow was observed in aqueous malted rice solutions. In the experiment, the measurement of the pressure drop in a smooth pipe 2mm in diameter with the length of the test section of 100mm was carried out. The range of Reynolds number based on the viscosity of the solvent, tap water is from 500 to 8000. We soaked the drying malted rice in tap water for about one hour, and then double the amount of tap water was added into the solutions. The malted rice solutions were filtered out by a cloth filter. After the amylase was cultured for 48 hours maintaining it 35℃, the solutions were tested. We obtained about 30% in the maximum drag reduction ratio for a pipe friction.
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Akiyoshi Kuroda, Masayuki Wakazono
Article type: Article
Session ID: 2327
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Numerical simulation of drag reducing flow by Toms effect is carried out using the equilibrium dumbbell element model proposed by the authors. The drag reduction up to 37% drag reduction rate was reproduced by DNS of 2D channel flow in the previous study. In the present study, new character is added on the model, say, the dumbbell element which simulate a polymer can be cut by the stretching force in the fluid. Simulations of 2D channel flows (Re_□=120-600) are carried out and the drag reduction up to 50% drag reduction rate is reproduced by the modified model.
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Satoshi OGATA, Kohei SAKAI, Kensuke KANDA, Ming YANG
Article type: Article
Session ID: 2328
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The velocity profile of a dilute polymer solution near the wall surface in a microchannel was clarified using evanescent wave illumination and a particle tracking velocimetry system. Fluorescent particles with a diameter of 100nm were used as tracer particles. The test fluids were polyethylene-oxide (Peo15) solutions at 5 ppm and distilled water. It was clarified that the velocity profile of the dilute polymer solution decreases significantly compared with that of water within 200nm of the wall surface. Brownian motion of the particle near the wall surface was suppressed by the polymer solution, and the suppression was emphasized under the flow condition.
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Atsushi YAMASHITA, Kazunori YASUDA
Article type: Article
Session ID: 2329
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Three dimensional velocity profiles of polymer solutions were directly measured in a microhannel with rectangular cross sections. The test fluids are 0.2 wt% aqueous solutions of polyacrylamide whose molecular weights are 6×10^6 (fluid L) an 1.9×10^7 (fluid H). The microchannel was made of PDMS and it is mounted on the glass plate. The velocity profiles in the width direction and in the depth direction were discussed. Consequently, for each test fluid, an apparent slip was observed on the PDMS wall. A slip layer is supposed to cause the apparent slip. This apparent slip on the PDMS wall significantly affects the velocity profile in the flow of polymer solution through a PDMS microchannel.
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Yuichiro IDE, Shinji TAMANO, Motoyuki ITOH, Kazuhiko YOKOTA
Article type: Article
Session ID: 2330
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Using particle image velocimetry (PIV) system, a ring vortex shedding phenomenon observed in the confined swirling flows of polyacrylamide (PAA) solutions whose concentration was 0.5 wt% was investigated. It was found that the fluid within the ring vortex formed near the rotating disc rotates with semi-rigid body rotation, where the angular velocity of ring votex was about 0.9 times that of the rotating disc. The high shear layer was found to exist at the boundary between the ring vortex and the outer large-scale secondary flow. After the ring vortex was shed, the surrounding large-scale secondary flow rushed into near the rotating axis, so that the strong axial flow was observed near the rotating axis.
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Takashi Koshiba, Takehiro Yamamoto
Article type: Article
Session ID: 2331
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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We examined an elongational viscosity for dilute polymer solutions by a filament stretching rheometer. The two aqueous solutions of PAA (Polyacrylamide) with different concentrations were used as test fluids. An elongational force acting on liquid in stretch deformation was estimated by a pressure transducer. In images of liquid filament for 0.005wt% PAA solution, the asymmetry of diameter profile with respect to the midpoint of filament were appeared. It was found that the response of pressure to the elongational deformation was closely connected to the transition of filament configuration. However, developing the stretch deformation with time, the necking of filament occurred at a certain time. After the occurrence of filament necking, it was confirmed that the elongational viscosity suddenly increased.
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Tsutomu TAKAHASHI, Toshihiro KAWANO, Masataka SHIRAKASHI
Article type: Article
Session ID: 2332
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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New measurement technique for the first normal stress difference using by a conventional rheometer with concentric cylinder flow cell is developed. The conventional rheometer which can control the up and down speed of the cylindrical bob and can also measure the thrust force is used in this technique. The other additional instruments or the optional parts are not required. The cylindrical bob is pushed down at a constant velocity into the sample filled in the cap. The resistant force acting on the bob is measured during this motion. The resistant force is caused by the buoyancy, the shear stress acting on the side surface of the bob and the pressure acting on the top and bottom of the bob. The buoyancy and the shear stress can be calculated from the shape of the bob and the moving velocity. If the entry and exit loss can be ignored, the pressure caused by the first normal stress difference can be evaluated from the thrust force and the information of the shear viscosity.
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Daisuke SEKINE, Nobuaki SATO, Tsutomu TAKAHASHI, Masataka SHIRAKASHI
Article type: Article
Session ID: 2333
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Effect of elasticity on the potential flow pattern in a Hele-Shaw cell is investigated by using three polymer solutions. While the inertia effect of Newtonian fluid causes the streamline separate from the body at its rear side, the elasticity of polymer solutions generates recirculating bubble around the upstream stagnation point. Regions for the potential flow, the inertia-affected and the elasticity-affected patterns are presented on the Re-We plane.
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Shunsuke TAKEDA, Uichi NISHIZAWA, Masaharu KAMEDA
Article type: Article
Session ID: 2334
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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This study focuses on shock oscillation around an external compression supersonic air-intake that called buzz. We carried out flow visualization by schlieren method with a high-speed video camera, and the measurement of static pressure fluctuation around the intake entrance, in order to investigate the effects of air-bleed from the entrance. It is found from the schlieren images that the air bleed suppresses the amplitude of shock oscillation and decreases its dominant frequency. High frequency components are generated in the static pressure fluctuation with the air bleed. This suggests that a new feedback loop is formed around the slit for the natural bleed.
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Md.Mahbubul Alam, Shigeru MATSUO, Masanori TANAKA, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2335
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A new passive control technique of cavity-induced pressure oscillations has been investigated numerically. A leading edge cutout fitted at the upper part of the front wall of a square cavity is studied at Mach number 1.83 at the cavity entrance. The results showed that the introduction of a cutout at the front wall of a square cavity change the flowfield in a favorable way such that some of the undesirable effects resulting from supersonic cavity were minimized. The results also showed that resultant amount of attenuation of oscillations were dependent on the depth of the cutout used as a controller of cavity-induced acoustic oscillations.
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Shigeru MATSUO, Md.Mahbubul Alam, Masanori TANAKA, Toshiaki SETOGUCHI
Article type: Article
Session ID: 2336
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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A computational investigation has been carried out to determine the effectiveness of plates fitted horizontally and vertically to suppress cavity-induced acoustic oscillations in supersonic flow. The results showed that the introduction of plates in a square cavity changed the flow field in a favorable way such that the upstream compression waves became weaker and the disturbance of the shear layer by the reflected compression waves was not strong enough to regenerate the instability waves to sustain the process by completing the feedback loop. The results also showed that, resultant amount of attenuation of acoustic oscillations was dependent on the depth of the vertical plate used as an oscillation suppressor.
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Hajime ITOH, Taihei KAHISBE
Article type: Article
Session ID: 2337
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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Experimenrtal study is conducted on the effect of corner angle on the scale of upstream influence in the shock wave/boundary layer interaction flow field on a two-dimensional corner model. Flow visualizations using schlieren and glow discharge techniques are performed in a hypersonic gun tunnel at Mach number 10 and Reynolds number based on the chord length 2.1×10^5. The corner angles studied are in the range from 10°to 30°at intervals 2°. The scale of upstream influence shows a characteristic increase with increasing corner angle.
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Daisuke ONO, Taro HANDA, Toshiyuki AOKI, Mitsuharu MASUDA
Article type: Article
Session ID: 2338
Published: September 15, 2006
Released on J-STAGE: August 01, 2017
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The three-dimensional flow structure induced by normal shock wave/turbulent boundary-layer interaction in a transonic diffuser is investigated by the numerical simulation. This simulation is compared quantitatively with the results of pressure measurement, and represents good agreement. The computational flow has the complicated shape of the boundary layers and three-dimensional vortices generated at the foot of bifurcated shock wave. The vortices are evidenced experimentally in the oil-flow surface visualization. The computational result reveals that the complicated wave configuration is formed at the diffuser corner. The simple flow model is constructed by considering this wave configuration. This model can explain qualitatively well the three-dimensional flow characteristics.
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