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Article type: Cover
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Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Article type: Appendix
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App1-
Published: September 20, 2002
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Article type: Index
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Toc1-
Published: September 20, 2002
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Takanori ISHIDA, Tsutomu TAKAHASHI, Masataka SHIRAKASHI, Tomiichi HASH ...
Article type: Article
Pages
1-2
Published: September 20, 2002
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The Hele-Shaw cell is used to examine the effect of elasticity on the flow patterns of two-dimensional potential flow. Flows around a circular cylinder and two abruptly converging-diverging channels with different throat lengths are tested for a Newtonian fluid (water) and a PAA-solution. When the flow rate is higher than a certain value, the streamlines of the PAA-solution near the upstream stagnation point of the circular cylinder are shifted upstream separating from the cylinder surface, while streamlines approach to the cylinder surface near the downstream stagnation point. In the flow through the abruptly converging-diverging channels at shear rates higher than a critical value, a pair of vortices is formed on both sides of upstream abruptly converging section, while the streamlines attach to the wall at the downstream abruptly diverging section.
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Takehiro YAMAMOTO, Takanori SUGA, Kiyoji NAKAMURA, Noriyasu MORI
Article type: Article
Pages
3-4
Published: September 20, 2002
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Coating flows of polymeric liquids in a pipe was studied. A bubble of air was injected into a pipe filled with a test fluid to form hydrodynamic coating on a pipe wall. The film thickness was evaluated by hydrodynamic fractional coverage m. The fractional coverage was characterized using the capillary number Ca and the Weissenberg number We. The film was thinner than that of the Newtonian case at the same Ca when the viscous property was dominant, i.e. We was small. Shear-thinning viscosity made the film thin. On the other hand, the film became thicker than the corresponding Newtonian results at large We because of normal stress effect.
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Takashi Koshiba, Noriyasu Mori, Kiyoji Nakamura, Akinori Kishine
Article type: Article
Pages
5-6
Published: September 20, 2002
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In order to clarify the details of the E.O.R mechanism using polymer solutions, the flow of polymer solutions penetrating into the Newtonian fluid (machine oil) in undulating slit channels was examined experimentally. Test fluids were the solutions of 0.01wt% PAA(polyacrylamide) with a different viscosity of solvent. From the observation of flow pattern, the shape of the interface between the both fluids is closely connected to the steady shear viscosity. Furthermore, it is found that the addition of PAA is effective for the recovery of the Newtonian fliud.
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Hiroshi SUZUKI, Hiroshi ISHIBA, Hiromoto USUI
Article type: Article
Pages
7-8
Published: September 20, 2002
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Flow visualization experiments have been performed in order to find the optimal geometric condition of heat transfer augmentation method using viscoelastic fluid instead of Newtonian fl uid for a cavity flow. In the experiments, rib height was kept constant and rib width was changed in three steps. From the results, when rib length is short, the viscoelastic fluid is found to penetrat deeply in cavities between ribs by Barus effect. In these conditions, the recirculating region observed in cavity flow of water system effectively reduces. Then, short-rib system can be expected to be effective for heat transfer augmentation in cavities between ribs.
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Nariaki HONDA, Hiroshi YAMAGUCHI
Article type: Article
Pages
9-10
Published: September 20, 2002
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Flow of viscoelastic fluid contained between a rotating outer sphere and a stationary outer hemisphere is studied experimentally. In the present investigation, relatively low-concentration polyacrylamide-water solutions are used as viscoelastic fluid, and for sake of comparison glycerin-water solutions are used as the Newtonian fluid. In experiments, the measurements results of torque and thrust showed strong dependence on Reynolds number, a gap ration, and thrust characteristics.
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Masahito HATTORI, Ikuhisa GOTO, Shuichi IWATA, Hideki MORI, Tsutomu AR ...
Article type: Article
Pages
11-12
Published: September 20, 2002
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A new singular finite element method for the viscoelastic flow problems was investigated. As for a small core region near singularity, we adopted a special γ^<-0.5> type element for elastic stress and pressure, and a special γ^<0.5> type element for velocity, where we intentionally removed a nodal point from the position of singularity, and then each element contained 12 nodes. It was found that the new method can predict successfully the die swell flow of viscoelastic fluids at a higher Weissenberg number over We=70 with less spurious oscillations near the die-lip.
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Kunio SHIMADA, HIDETO Kanno, Junji OGAWA, Shigemitsu Syuchi, Shinichi ...
Article type: Article
Pages
13-14
Published: September 20, 2002
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We proposed a new type of viscous fluid damper with complex fluids : MF(magnetic fluid), MR(magneto-rheological fluid), MCF(magnetic compound fluid). The damper never has the sedimentation of particles. To investigate the effect of damping, we measured displacement of dampers under the fluctuating magnetic field. By comparing among the differences of damping effects by three kinds of the fluid, MCF has the largest damping effect. As the fluctuating magnetic field, the proposed damper is effective for semi-active damper.
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Fumito KAJITANI, Takuya KAMEMIZU, Masaharu KAMEDA, Mie ICHIHARA, Uichi ...
Article type: Article
Pages
15-16
Published: September 20, 2002
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A new method for measuring dynamic viscoelasticity of highly viscous fluids was developed. The strain-stress relation was obtained from the motion of a bubble subjected to pressure fluctuation. A set of basic equations was derived, which represented the relation between frequency response of bubble motion and dynamic viscoelasticity. A pilot apparatus was constructed to perform a preliminary test, in which commercial silicone oil (kinematic viscosity 1m^2/s) was used as a test material. The dynamic viscoelasticity for the silicone oil was successfully obtained up to 200Hz, which is impossible to obtain by conventional rotating rheometers.
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Shigeki IMAO, Yasuaki KOZATO, Toshio TANAKA, Tomokazu HASEGAWA
Article type: Article
Pages
17-18
Published: September 20, 2002
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The flow behavior of polymer solutions among cylinders in a rectangular duct has been studied by means of pressure loss measurements, flow visualization and particle image velocimetry. Cylinders are located alternate position and there are narrow gap side and wide gap side. The fluids used here are polyacrylamide 300ppm solution and Xanthan gum 800ppm solution, which show nearly the same shear viscosity. In the case of PAM solution, pressure loss becomes very large compared with the case of Xanthan gum solution, and the former hardly pass through the narrow gap side. This fact may be due to high extensional viscosity of PAM solution. In addition, difference of flow pattern in z-direction is studied and three dimensionality of the flow is clarified.
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Hideyuki Takagi, Hiroshi Mizunuma
Article type: Article
Pages
19-20
Published: September 20, 2002
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At the exit of a Couette flow cell, the spatial distribution and the temporal change of velocity were measured under sharkskin-like instability. A particle tracking method and laser Doppler velocimetry were applied through microscopic optical system. Under the flow instability, high velocity was detected when adhesion failure inside the cell induced a valley on the free surface, and low velocity was detected when inside adhesion recovery induced a ridge. The high velocity corresponds to complete slip at the cell exit, and it is suggested that weak slip occurs before adhesion failure. Inside the cell, adhesion failure causes the cavity penetration from the cell exit, which induces flow stagnation upstream of adhesion failure. This stagnation relaxes high shear upstream of the region of adhesion failure, and then suppresses the increase in the penetration length of cavity.
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Hideo ASAMA, Tomiichi HASEGAWA, Takatune NARUMI
Article type: Article
Pages
21-22
Published: September 20, 2002
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Birefringence of a viscoelastic fluid was measured in a flow through a slit. CTAB(cetyltrimethylammonium bromide, 0.01mol/l) : NaSal(sodium salicylate, 0.07mol/l) water solution was used as a test fluid. Since thread-like micelles are constructed in this system, the test fluid shows viscoelasticity. First normal stress difference and shear stress of CTAB : NaSal solution were measured by the jet thrust method and the capillary method, and the viscoelasticity was confirmed. Measurements of birefringence were performed along the centerline of jet issuing from the slit at various flow velocities. It is thought that disintegration of thread-like micelles occurs in the slit when the flow velocity was high, and reconstruction of thread-like micelles appears downstream of the exit.
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Masaru SHINOHARA
Article type: Article
Pages
23-24
Published: September 20, 2002
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The present study investigates the motion of a magnetic fluid drop settling in an incompressible viscous fluid bounded by a vertical circular cylinder. The velocity of a settling magnetic fluid drop inside a cylinder depends on the size of a magnetic fluid drop and the strength of a magnetic field. Two coils are placed as their axes to be coincide with the cylinder axis and provided the magnetic field for the tests. Under the upper coil the center of the drop is forced upwards, but the velocity of the drop is not always decreased. At the middle point between two coils, there is no magnetic force on the center of the drop. But the drag on the drop is reduced due to the change of the shape of the drop by the magnetic field and the velocity of the drop is increased.
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[in Japanese], [in Japanese], Akira NAKAGAWA, [in Japanese], Masumi SA ...
Article type: Article
Pages
25-26
Published: September 20, 2002
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The magnetic fluid jet generated by the vibration of an annular permanet magnet-magnetic fluid system was investigated experimentally making use the vibration-testing system. The dynamic behavior of narrow magnetic fluid jet and magnetic fluid surface were analyzed by a three-dimensional motion analysis system composed of two high speed digital cameras. It was found that narrow magnetic fluid jet and homogeneous size drops can be produced by combination of certain excitation frequency and amplitude. Effect of the excitation amplitude on the jet formation of magnetic fluid and the atomization characteristics was revealed in detail.
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Hiroshi YAMAGUCHI, Shigemitsu SHUCHI, Koji SAKATANI
Article type: Article
Pages
27-28
Published: September 20, 2002
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Boiling heat transport characteristics were verified for a temperature sensitive magnetic fluid, to which the organic fluid was mixed, yielding a binary-carrier-fluids magnetic fluid. Substantial increase of heat transport capability was achieved in comparison with in ordinary magnetic fluid. In the present study, n-hexane, which has lower boiling point than that of kerosene (mother carrier fluid), was mixed. It was found that the heat transport capability could be controlled by applying magnetic field as well as altering the mixing content of the sub-carrier fluid.
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Yasumasa ITO, Kouji NAGATA, Satoru KOMORI
Article type: Article
Pages
29-30
Published: September 20, 2002
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The effects of high-frequency ultrasound, mean fluid shear, and buoyancy under unstable stratification on turbulent mixing with a rapid chemical reaction were experimentally investigated in liquid mixing-layer flow downstream of a turbulence-generating grid. The results show that although turbulent mixing is promoted by ultrasonic irradiation, mean fluid shear, and buoyancy convection under unstably stratification, the amount of chemical product in grid-generated turbulence with ultrasonic irradiation or under unstable stratification in much larger than that in the sheared case. It is also found that turbulent mixing under ultrasonic irradiation and unstable stratification can promote turbulent mixing at the smaller scales and under more weakly sheared conditions, compared with the sheared case.
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Yasuo NAKANISHI, Toshihiro FUNANAKA, Kouji NAGATA, Satoru KOMORI
Article type: Article
Pages
31-32
Published: September 20, 2002
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The effects of rainfall on both CO_2 transfer and turbulence structure at the air-water interface were investigated through laboratory experiments in an open channel. Instantaneous streamwise and vertical velocities in the water flow were measured using a laser Doppler velocimeter (LDV). To estimate the CO_2 transfer velocity across the air-water interface, gas-absorbtion experiments were also conducted. The results show that rainfall enhances the turbulence intensities and decreases the Reynolds stress at the interface. The CO_2 transfer velocity K_L increases with increasing rainfall rate. This means that rainfall enhances the turbulent mixing and mass transfer at the air-water interface.
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Kunio SHIMADA, Shigemitsu Syuchi, Shinichi KAMIYAMA
Article type: Article
Pages
33-34
Published: September 20, 2002
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We succeeded the cluster of particles aggregation like a chain or needle by extracting from the colloidal suspension. The colloidal suspension is magnetic compound fluid (MCF) which has been developed as one of intelligent or smart fluid by one author. Also, we discovered that the size of the cluster has a memory of the applying magnetic field strength and that it has a function of the magnetic field strength. Therefore, we can control the size of the extracted or produced cluster with wide range from μm to mm. It has superparamagnetism and then we can call it a magnetic cluster.
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Takatsune NARUMI, Yousuke OHMI, Tomiichi HASEGAWA
Article type: Article
Pages
35-36
Published: September 20, 2002
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We have investigated flow properties of liquid crystals under electric fields in an oscillatory squeezing flow. Micro Fourier Rheometer was utilized to estimate the dynamic visco-elasticity and electric rheological (ER) effects. Similar ER effect to that in steady flow, i.e. increase in dynamic viscosity due to the electric fields, is observed, but apparent viscosity estimated in a high frequency region under the electric fields is smaller than that measured with no electric field. Elastic property in the oscillatory squeezing flow becomes remarkable in middle region where both influences from electric fields and the shear flow are effective. These complicated ER effects may be construed with magnitude of moments acting on the liquid crystal generated with electric field and shear.
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Atsushi TERADA, Tomohiro TSUJI, Shigeomi CHONO
Article type: Article
Pages
37-38
Published: September 20, 2002
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Numerical simulation of nematic liquid crystalline flow between rotating parallel disks has been performed using the Leslie-Ericksen continuum theory. It is assumed that the director lies in the shear plane and that the velocity profile is linear in the gap direction of the two disks. For a tumbling-type liquid crystal both the two-dimensional analysis and the Carlsson's model, in which molecular field elasticity in the radial direction is ignored, can predict step-like changes of the director orientation angles in the radial direction at high Ericken numbers. However, the orientation angles are discontinuous at tumbling regions for the Carlsson's model, whereas they are continuous for the two-dimensional analysis. A peculiar behavior observed in a light intensity experiment reported by Carlsson et al. that dark rings move from the disk periphery to its center is satisfactorily simulated by the two-dimensional analysis.
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Shinji Toga, Tomiichi Hasegawa, Takatsune Narumi
Article type: Article
Pages
39-40
Published: September 20, 2002
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It is known that the colloidal dispersion of polystyrene spheres enhances the electrostatic repulsion among the spheres by deionized processing while it enhances the van der Waals attraction by electrolyte concentration. This report describes the experimental result on the flow of the dilute colloidal dispersion of the fine polystyrene spheres passing through a small orifice, where it is shown that the colloidal particles give a stability or an instability effect on the orifice flow depending on the electrolyte density. The measured flow rates fluctuate with strong electrostatic repulsion. The increase in the electrolyte density stabilizes the orifice flow, whereas excessively high electrolyte density causes instablity in flow rates.
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Kazunori YASUDA, Noriyasu MORI
Article type: Article
Pages
41-42
Published: September 20, 2002
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Orientation and concentration distributions of shore fibers in a concentrated suspension flow through a complex geometry are presented. Fibers are oriented perpendicular to the streamline in an abrupt expansion region. Furthermore fiber orientation distribution is not symmetrical to the channel centerline in downstream region of a L-shaped corner. These orientation states, which are owing to fiber-fiber interaction, are not observed in a dilute fiber suspension flow. Fiber concentration has a flat distribution over a channel width in concentrated suspension, but has a maximum near a channel wall in dilute one.
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Kazuhiro KINOSHITA, Hiroshi YAMAGUCHI
Article type: Article
Pages
43-44
Published: September 20, 2002
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Rheological characteristics of bamboo fiber and glass fiber compound plastic were examined experimentally. In the present study, rheological data for the shear viscosity, the storage modulus and the loss modulus of compound plastic of polyproylene with maleic acid mixing with various contents of bamboo fiber, were reported in comparison with equivalent glass fiber compound plastic. According to SEM visual information, bamboo fibers have short rod-like structure with high fiber-fiber interaction in the compound, while the glass fibers have long needle structure forming entanglement in the compound. It was obtained that the rheological data showed clear difference based on the different structures in the compounds.
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Noriyasu MORI, Toshihide TSURUKAWA, Kiyoji NAKAMURA
Article type: Article
Pages
45-46
Published: September 20, 2002
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Relation between flow properties and micellar structures of surfactant solutions is investigated. Small-amplitude oscillatory measurements suggest that salt concentration significantly affects the network structure of micelles. The flow curves obtained from a capillary rheometer show a leveling-off of wall shear stress at intermediate shear rate region. It is supposed that this leveling-off behavior is connected with the collapse of micellar network.
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Manabu KATOH, Tsutomu TAKAHASHI, Masataka SHIRAKASHI
Article type: Article
Pages
47-48
Published: September 20, 2002
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Rhelogical properties in steady planar elongational flow of CTAB/NaSal aqueous solution, which forms wormlike micelles and shows viscoelastic property, were investigated. 4-roll mill flow cell was used to create steady planar elongational flow. The planar elongational stress was measured by using a flow-birefringence technique which is based on the stress-optic rule. In addition, the planar elongation rate was accurately measured by the motion analysis of tracer particles. The planar elongational viscosity was evaluated from both results and it showed the elongational thinning as the same of the shear thinning. The planar elongational viscosity, which was measured by using 4-roll mill flow cell, was compared with one, which was measured by using squeeze flow cell, and they showed good agreement. Trouton ratio was kept 4 in both Newtonian region and elongational thinning region. The flow instability was observed in 4-roll mill flow cell at a certain planar elongation rate that was lower than the case of shear flow instability
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Hiroshi WATANABE, Kazunori SORIMACHI, Tomiichi HASEGAWA, Takatsune NAR ...
Article type: Article
Pages
49-50
Published: September 20, 2002
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The drag reduction effect was experimented in turbulent flows through a pipe of the diameter 3.17mm for surfactant solutions. As water, Newtonian fluids is not shown the drag reduction. In surfactant solution, dilute Ethoquad aqueous solution give similar results in the case of Newtonian fluids, and Ethoquad aqueous solution adding NaSal have the tendency of large drag reduction. For the solutions which are shown the drag reduction, in low frequancy region, the power spectrum of these are higher than that of water.
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Hironori TAGOKU, Shu SUMIO, Seiji GOTO
Article type: Article
Pages
51-52
Published: September 20, 2002
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This report describes flow properties of surfactant aqueous solutions in pipe junction with dividing angle of 90 degrees. Ethquard was used as surfactant and its concentration was 100ppm. Energy losses due to dividing flow and pipe friction losses before and behind junction were measured. The pipe friction factors before and behind the junction decreased than those for water. However, the drag reduction and behind the junction were less than before it. The critical Reynolds number (Re_c) also decreased. The dividing loss coefficients became large than in the water at Reynolds number under Re_c and agreed with those for water at beyond Re_c.
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Komei SUZUKI, Hiroshi KOIBUCHI
Article type: Article
Pages
53-54
Published: September 20, 2002
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The liquid-gel phase transition of bilayer lipid membranes (BLM) is known to be of the first order and closely related with internal degrees of freedom of the amphiphilic molecules. It is also well known that the Potts model undergoes a first order phase transition. Therefore we study the liquid-gel phase transition of the BLM by 10-states Potts model on triangulated surfaces by Monte Carlo simulations. We find that there are non-trivial effects of both fluidity and shape fluctuations on the liquid-gel phase transition and moreover that this first order phase transition is altered to a second order one.
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Atsushi NIDAIRA, Hiroshi KOIBUCHI
Article type: Article
Pages
55-56
Published: September 20, 2002
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Surfactant molecules form an adsorbed monolayer on the surface of water. It is possible that the adsorbed monolayer has both an ordered state and a disordered state of molecules. As a consequence, a phase transition is expected to occur between these two states. It is also expected than an interaction between the molecules is described by the well-known XY model. We study numerically an internal phase transition of the adsorbed monolayer by using XY model defined on triangulated surfaces. We find that the shape fluctuation of surfaces strengthen the internal phase transition of the model.
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Hajime KATOH, Tetsuro OBARA, Shigeharu OHYAGI
Article type: Article
Pages
57-58
Published: September 20, 2002
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A phenomenon of shock wave diffraction is often occurred by the explosions of combustible gases and cause serious damages around a source of the shock wave. Therefore it is important to investigate flow-fields behind diffracted shock wave. In this study, experiments are carried out to investigate the flow-field of shock wave diffraction in a Mach number ranged from 1.3 to 5.2. As a result, the behavior is agreed between experimental and numerical results and an empirical equation to evaluate maximum pressure produced by the reflection of diffracted shock wave is obtained.
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Akisato MIZUNO, Katsuhiko ARAI, Akio KAWANO
Article type: Article
Pages
59-60
Published: September 20, 2002
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In the ultrasonic gas flow meter, measurement errors are crucial problem especially in lower flow rates. The authors investigated numerically the flow inside the measurement tube, where velocity distributions vary substantially due to a wide range of Reynolds numbers, which are from 5 to 10,000. The result showed that in the low Reynolds number range the flow rate converted from the sonic traveling time showed good agreement with the theoretical value based on parabolic velocity profile. In turbulent range, on the other hand, the power law of velocity distribution gave good agreement. The mid-range was interpolated to construct the calibration curve obtained through numerical experiments.
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Shinji ODA, Takashi SHIMADA, Yoshiya TERAO, Masaki TAKAMOTO
Article type: Article
Pages
61-62
Published: September 20, 2002
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A servo positive displacement (PD) flowmeter has been developed in order to achieve wide range-ability, a long-term stability and high accuracy in liquid flow measurement. The servo control system compensates for mechanical friction, so that it controls the leakage from the clearance by detecting the pressure difference between the inlet and the outlet of the PD flowmeter. Therefore the characteristic of the flow inside the flowmeter was investigated through flow visualization by using a transparent flowmter model in order to optimize the position of pressure tap.
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Takayuki SAITO, Masanori Fukawa, Akinori Kumagai
Article type: Article
Pages
63-64
Published: September 20, 2002
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Probe methods are widely used for measuring void fraction and bubble characterizations in turbulent gas-liquid two-phase flows. The knowledge of interfacial motion and/or interfacial deformation of a bubble being in contact with the probe as well as its motion of the center of gravity are insufficient. In addition, relationship between the interfacial deformation and the output signal from the probe is unknown as well as influence of the interfacial deformation on the measuring accuracy. In the present paper, interfacial motion, including interfacial velocity, and magnitude of the deformation of a bubble are discussed on the basis of visualization of them using two sets of high-speed video camera and microscope. Relationship between the interfacial deformation and the output signal from the probe is quantitatively discussed on the basis of simultaneous measurement of bubble deformation and the probe signal.
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Shuyang CAO, Tetsuro TAMURA
Article type: Article
Pages
65-66
Published: September 20, 2002
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Roughness effects on the turbulence structures over a two-dimeansional rough hill are investigated experimentally and numerically in this study. The hill concerned has a maximum slope of about 32゜ with a seperation bubble formed at its leeside. The results of smooth wall condition and rough wall condition (roughness density 45%) are compared to make clear the roughness effects. On the rough wall condition, the reattachment length is getting longer, and the wake flow is influenced by the oncoming turbulence within a longer region. The power spectrum of the velocity fluctuation measured at the wake region decreases in the low frequency regime and increases in high frequency regime much more than on the rough wall condition.
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Akihiro EBISAWA, Shuyang CAO, Tetsuro TAMURA, Makoto TSUBOKURA
Article type: Article
Pages
67-68
Published: September 20, 2002
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In this paper, the thermally stratified boundary layer developed over a rough-wall is investigated. Two kinds of turbulent boundary layer flow with α=1/7 and α=1/4 are generated by placing roughness elements on the wall of wind tunnel, in which the floor and flow temperatures can be controlled. The changes of the turbulence characteristics of the neutral flow on the stability are shown as follows : 1) The exponent of velocity profiles increases with stability. 2) The turbulent intensity decreases with stability near wall area. 3) The effect of thermal stratification on turbulence become obvious at larger exponent of velocity profile.
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Nobumasa SEKISHITA, Hideharu MAKITA, Shirohisa KOBAYASHI
Article type: Article
Pages
69-70
Published: September 20, 2002
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The present study aims to produce large-scale atmospheric-like boundary layers in a wind tunnel by a turbulent shear flow generator. The resultant turbulence field had large values of turbulence intensity, Reynolds stress and turbulent eddy scale and the vertical distributions of these turbulence quantities resembled the ones obtained in a natural atmospheric boundary layer. A wide-spread inertial subrange existed in its energy spectra and its width was almost equivalent to those observed in natural turbulence fields. The resultant turbulence characteristics confirmed that the present experimental scheme made it possible to conduct precise simulations of large-scale turbulence phenomena in natural atmospheric boundary layers in a wind tunnel of a laboratory scale.
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Hitoshi SUGIYAMA, Chiriki WATANABE
Article type: Article
Pages
71-72
Published: September 20, 2002
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Numerical analysis has been performed for three-dimensional developing turbulent flow in a U-bend of strong curvature with rib-roughened walls by using an algebraic Reynolds stress model. Special attention is paid for the developing turbulent flow in U-bend with positive and negative rotations in this study. It has been pointed out as a characteristic features from the experimental result that positive rotation leads to a more uniform velocity distribution within bend, whereas, the high momentum fluid remains closer to the inner side with negative rotation. The present method could relatively predict such velocity profiles and reproduce the separated flow generated near the outer wall which is just located at downstream of curved duct.
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Takatsugu KAMEDA, Hideo OSAKA, Shinsuke MOCHIZUKI
Article type: Article
Pages
73-74
Published: September 20, 2002
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Measurement of conditional sampling (Quadrants analysis) and high moment quantities have been performed in the vicinity of a roughness element for the boundary layer over a k-type rough wall, which consists of two-dimensional square ribs arrayed with pitch ratio of 4,having a ratio λ_s of cavity width b to a pitch length λ of 0.75. Comparing with the results of λ_s=0.5 and 0.7,the contribution to the Reynolds shear stress from each event and the vertical turbulent flux of the streamwise turbulent energy and the Reynolds shear stress depend on the wall roughness. In the near wall region influenced directly by a roughness element of λ_s>0.5∿0.7,the sweep event largely dominates to the Reynolds shear stress and the wall ward turbulent motion is revealed from the results of the vertical turbulent flux.
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Shinsuke MOCHIZUKI, Takanori NAKAMURA, Kentaro MURAMOTO, Hideo OSAKA
Article type: Article
Pages
75-76
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Adverse pressure gradient effect on the local similarities in turbulent boundary layers was investigated experimentally under the equilibrium condition with power law variation of free stream velocity. An equilibrium boundary layer in which equations of motion can be reduced to an ordinal differential equation with liner development of length scale and constant sin friction coefficient was established over certain streamwise extent, x=4.35∿4.7[m]. In logarithmic velocity profile, Karman constant takes the same value of κ=0.41 under zero pressure gradients, however, additive constant is somewhat smaller than C=5.0. New power law was applied to velocity defect profile in the outer layer and difference between zero pressure gradients and adverse pressure gradient was found in additive constant.
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Yuji Okita, Masashi Ichimiya, Katsutaka Nakamura
Article type: Article
Pages
77-78
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The purpose of this paper is to study in detail the flow over an inclined fence in a turbulent boundary layer, as basic research which issues from promoting heat transfer and the decrease of the pressure drop. The fence height h set in a turbulent boundary layer is 3mm(μ_rh/ν≑ 75,μ_r : friction velocity, ν : kinematic viscosity) and setting angle of a fence is 20゜ in the free stream direction. The velocity profiles in the downstream of the fence were measured by I-shaped hot-wire probe and we investigated turbulence characteristics. Consequently, we clarified the skewness profiles and the flatness profiled, and the change of bursting using by the VITA Technique.
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Masashi ICHIMIYA, Yasuaki SHIBASAKI
Article type: Article
Pages
79-80
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Relaminarization properties of the turbulent boundary layer by a sink-flow are experimentally investigated. Fluctuating velocities and the Reynolds stress decreased with the relaminarization within the sink-flow section. The decrease in the wall-normal fluctuating velocity was more remarkable than that in the streamwise fluctuating velocity. The normalized intermittency frequency decreased and non-turbulent region came close to the wall. The intermittency of the wall-normal velocity fluctuation became more remarkable than that of the streamwise component. Contributions of the sweep process to the coherent structure decreased and the inward interaction became dominant.
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Msatoshi SANO, Tomohiro SUZUKI, Kazuki SHIRATORI
Article type: Article
Pages
81-82
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Experiments have been performed for a turbulent channel flow obstructed with a triangular cylinder. The clearance between the wall and the triangular cylinder is changed in three steps. The triangular cylinder of four kinds of different angles is used. A split hot film probe is used for the measurements of velocity profile and turbulent intensity. At the clearance is large, the vortex shedding from the triangular cylinder is observed. However, the vortex shedding is suppressed at the small clearance. Enhancement of the heat transfer coefficients is related to the increase of turbulent intensity in the vicinity of the wall.
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Hitoshi SUGIYAMA, Takuya SAITO
Article type: Article
Pages
83-84
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Numerical analysis has been performed for the developing turbulent flow in compound meandering open-channel flow by using algebraic Reynolds stress model and boundary fitted coordinate system. The turbulent flow in compound meandering channel is one of the complicated turbulent flows, because the flow behavior is influenced upon many kinds of forces that are centrifugal force, pressure driven force and shear stress generated between main channel and flood plain. The flow of interest to study is one periodic compound meandering channel of five ones. The calculated results are compared with the experimental results including Reynolds stresses to clarify the validity of the present method. As a result of this calculation, it has been found that the present method is able to predict well the characteristic features.
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Hitoshi SUGIYAMA, Masaki SAKAMOTO
Article type: Article
Pages
85-86
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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An experimental study of development turbulent flow in a rectangular duct with staggered blocks for non-Newtonian fluid (0.1 wt.% CMC solution) has been carried out by using Laser-Doppler velocimeter. If has been well known that, addition of small amount of a polymer to water causes frictional drag reduction. After this phenomenon has been confirmed in a pipe flow and this rectangular duct flow, the measurement has been performed in the flow region between number 7 block and number 8 block for Newtonian (water) and non-Newtonian (0.1 wt.% CMC solution) fluids under the condition of the same flow rate (U_b=0.322m/s). As a result of this experimental study, it has made clear that the peak of streamwise velocity's generated in the central and wall side regions similarly and similar separation-reattachment region is produced behind blocks for both of the fluids.
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Taisuke SUGII, Yukinori SAKIYAMA, Shu TAKAGI, Yoichiro MATSUMOTO
Article type: Article
Pages
87-88
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The supersonic free jet of the gas mixture of different weight atoms results in a velocity slip and a temperature difference between the gas species. We obtain the rotational temperature distribution of a supersonic free jet of N_2/He gas mixture by electron beam fluorescence method. The acceleration of N_2 and the rotational temperature jump in front of the vertical plate were observed and it turned out that the temperature jump goes up with the increase in the mixture ratio of He.
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Keita TAKAMURA, Yukinori SAKIYAMA, Shu TAKAGI, Yoichiro MATSUMOTO
Article type: Article
Pages
89-90
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The chemical vapor deposition (CVD) process plays an important role in the rapid improvement of the semiconductor technology, but the thermo-fluid structures are not investigated experimentally enough so far. A coherent anti-Stokes Reman scattering (CARS) spectrometer combined with a supersonic free jet generator was built to investigate the rotational relaxation in the supersonic free jet of methane in the expansion region. Before the experiment, we calculated the CARS spectra of the ν_3 vibration to determine the required laser resolution and to acquire the information of the spectrum. A detailed description of the experimental apparatus and the calculated CARS spectra of several rotational temperatures are reported.
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Hideo MORI, Carl Dankert, Tomohide NIIMI
Article type: Article
Pages
91-92
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In the DLR-high vacuum plume test facility STG, experiments have been performed to study the expansion of supersonic plumes into vacuum with N_2 as a test gas. So far, the molecule number flux, the rotational temperature and the density were measured by the 2+2 REMPI technique with a stimulation wavelength of 283-284mm. This method is also suitable to measure the absolute flow velocity by the ion-time-of-flight (ion-TOF) method. This study is focused on the experimental methods of measure the flow velocity of rarefied plumes. The results of measurements in highly rarefied plumes taken on-axis for several stagnation temperatures are presented, and the measured angular velocity profiles (off-axis) are discussed and compared to the theory. The effect of the suction voltage on the flow velocity measurement by the ion-TOF method is also clarified.
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Tomohide NIIMI, Hideo MORI, Masaki YOSHIDA, Makoto KONDO, Yusuke OSHIM ...
Article type: Article
Pages
93-94
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Pressure measurement system using PSP (pressure sensitive paint) is the way for measuring O_2 partial pressure on the solid surface according to luminescence and its oxygen quenching. Recently, the usefulness of PSP has been expected. In this study, we apply two types of PSP to the pressure range lower than 1 Torr (133Pa), and examine PSP's fundamental properties such as luminescence intensity for abrupt change of pressure. Finally, we suggest the more suitable PSP for measuring the pressure on the solid surface in the low pressure range.
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