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Takuma KATO, Yasuyuki HATTORI, Shuichi IWATA, Hideki MORI, Tsutomu ARA ...
Article type: Article
Session ID: 1457
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The singular/decoupled finite element method (SFEM), which is enable to yield more smoothed results especially near the die-lip (singularity) than the ordinary FEM for solving the die-swell flow problems of viscoelastic fluids, have been applied to 4:1 axisymmetric sudden contraction flows of unit mode Giesekus model fluids for the purpose of testing an enhancement capability of SFEM to the other problem, and comparing our FEM / SFEM results with experimental data reported by Byars et al^<1)>. When substituting the extra stress into momentum equation, following two schemes are adopted: the rearranged substitution method (RS) and the direct substitution method (DS). At this moment, the simulations for FEM-RS, FEM-DS and SFEM-RS are successful. It is found that for the problems containing singularity, slight difference can be seen between RS and DS, i.e., the size of circular region obtained with RS-FEM and RS-SFEM are greater than those calculated with DS and the experimental results.
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Shuichi TANOUE, Ryuichi KAWACHI, Yoshiyuki IEMOTO, Hideki TOMIYAMA, Na ...
Article type: Article
Session ID: 1458
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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We tried to predict the parison shape in blow molding by non-isothermal viscoelastic flow simulation of a steady-state annular extrudate swell. The Phan-Thien Tanner (PTT) and the Carreau models including non-isothemal influence, were employed as the constitutive equation of viscoelastic and purely non-Newtonian fluid, respectively. Focused fluid was blow molding grade HDPE melt. Shape of extrudate swells greatly in the ratial direction because contraction flow is included in flow geometry of die. When an air flows around a parison, the temperature on the parison outer surface become decreased, but parison shape is almost independent of parison temperature at more than melting temperature.
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Zion SASAKI, Minori KUROIWA, Keisuke SHINOHARA, Hiroshi KOIBUCHI
Article type: Article
Session ID: 1459
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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We numerically study a shape fluctuation phase transition of membranes with new definition of the bending energy neglecting the fluidity of lateral diffusion. The canonical Monte Carlo simulations are performed on lattices which are uniform in coordination number. We find that the model undergoes a first-order phase transition between a smooth phase and a crumpled phase. The result is consistent with the one reported previously.
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Hiroshi KOIBUCHI, Jion SASAKI, Minori KUROIWA, Keisuke SHINOHARA
Article type: Article
Session ID: 1460
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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By canonical Monte Carlo simulations on fixed connectivity surfaces of spherical topology, we investigate a surface model whose Hamiltonian is defined by a linear combination of an area energy and an intrinsic curvature energy. We find three distinct phases; crumpled, tubular, and smooth. The first two are smoothly connected, and the last two are connected by a discontinuous transition. Surfaces become considerably slight in the tubular phase, which separates the crumpled phase and the smooth one.
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Noriyasu MORI, Shinsuke OGIRI
Article type: Article
Session ID: 1461
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Effects of polymer concentration and temperature on the developmental conditions and structure of wavy texture were experimentally studied using aqueous solutions of hydroxypropylcellulose (HPC). A variety of phases were observed at various HPC concentrations and temperatures: liquid crystalline (LC) phase, isotropic (I) phase and coexisting phase (LC+I). The wavy texture was occurred in LC phase and coexisting one with higher orientation order. The phase state affects the apparent shear strain at the onset of wavy texture, especially at low shear rates.
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Tetsuhiro TSUKIJI, Eitaro KOYABU, Keisuke NAKAYAMA, Tsuyoshi MITANI
Article type: Article
Session ID: 1462
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A circular pipe electrode are designed to control the pressure and the flow rate of the ER (Erectro-rheological) fluids. The shape of the electrode is a circular pipe and the some parts of inner surface in the pipe are the electrode. A liquid crystal mixture is selected as a homogeneous ER fluids and the pressure drop of the circular pipe electrode is measured for a constant flow rates. On the other hands, numerical analysis of the electric fields in the circular pipe electrode is conducted and the relations between the flow rate and the pressure are obtained numerically for various electric field intensities, which almost agree with experimental results. In the present numerical analysis, it is assumed that the viscosity of liquid crystal mixture is distributed in the flow field. The ER effect of a circular pipe electrode is discussed from the present calculated results.
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Shin SUGAWARA, Takatsune NARUMI, Tomiichi HASEGAWA
Article type: Article
Session ID: 1463
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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We have investigated the ER characteristics in smectic phase of a liquid crystal utilizing a parallel-plate type rheometer. The yield stress was evaluated in τ-sweep experiments. Under some electric field strengths, the yield stress was almost same as that obtained under non electric filed. In the DC electric fields above the threshold, the yield stress was increased and then saturated. An opposite trend was obtained in AC electric fields. It is considered that the smectic multi-domain structure would maintain against the shear stress and it became more aligned and stronger structure under the higher DC electric fields. But, the AC electric field would loosen the structure because of alternate electric moment on the molecule etc.
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Masashi YAMAGOU, Takatsune NARUMI, Tomiichi HASEGAWA
Article type: Article
Session ID: 1464
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In this research, we utilize the ER effect of liquid crystal to the lift and height control of a flat plate on radial flows as a fundamental test to the application of liquid crystal to hydrostatic bearing. The electric field was applied to the radial flow between the lifted plate and electrodes. Rectangular pulse wave with controlled duty ratio was employed to adjust the apparent viscosity of liquid crystal. We found that our method was useful to the height and parallelism control of the lifted plate and the lift obtained in the experiment was in good agreement with the estimation from ER effect of liquid crystal.
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Shigeomi CHONO, Tomohiro TSUJI, Tomoya KURASA
Article type: Article
Session ID: 1465
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Experimental Study on liquid crystal actuators is performed under a polarized microscope. The low molecular weight nematic liquid crystalline material is placed between parallel glass plates. The lower plate is fixed, and the upper can move freely. When 5V of electric field is imposed on the liquid crystalline material, the rod-like molecules re-align to the orientation direction perpendicular to the plates. During this re-alignment of the liquid crystalline molecules, the fluid flow, called back-flow, is induced. Because of the back-flow mechanism, the upper glass plate moves in a certain direction.
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Akihiro MAEDA, Takanori NAGAE, Tomohiro TSUJI, Shigeomi CHONO
Article type: Article
Session ID: 1466
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Fundamental research on flexoelectric effect of the nematic liquid crystals has been performed numerically using the Leslie-Ericksen continuum theory. The tumbling liquid crystal is confined in between parallel plates. The lower plate is fixed, while the upper one moves along x-direction. Once shear flow is applied, the tumbling liquid crystal is rotated and inclined in the z-direction by the flow. Then, Director degree of angle changes from minus to plus in x-y plane suddenly. It is gathered from director inclined in out-plane and approached at significant point that the angle is plus suddenly. The flexoelectric polarization has been estimated from the calculated molecular orientation field distance for the upper and lower plates. So tumbling liquid crystals occurs to bigger flexoelectoric polarization than aligning liquid crystals.
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Makoto MORITA, Tomiiti HASEGAWA, Takatune NARUMI, Toshio YOSHIDA
Article type: Article
Session ID: 1467
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper presents the experimental results of fluidity of liquids flowing through a porous membrane by applying voltage. We applied a voltage between the solution filled on both sides of the membrane and measured the flow rate through the membrane. It is found that the flow is generated toward the negative pole and the flow rate is increased by increasing minus voltages. Influence of the electroosmosis or electrophoretic migration on the flow is considered.
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Jun KENMOTSU, Hiromichi OBARA, Yasuaki MATSUDAIRA
Article type: Article
Session ID: 1468
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Functional fluid containing diamond particles generates the peculiar microscopic flow pattern with some rotational flows in the gap of electrodes under high voltage alternating current electric field. Their microscopic flow characteristics influenced by particle density and solvent viscosity were investigated with the measurement of a micro particle image velocimetry and the observation of a microscope. This functional fluid has four types of flow structures and shows five patterns of particle clusters. In particular, the rotational flows are typically generated under high electric field and low current frequency against any particle density conditions (l〜8wt.%) except the low particle density condition (0.2wt.%). Furthermore, the solvent viscosity condition affects the characteristics of the flow pattern.
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Seiichi SUDO, Yuji TAKAKI, Yasunari HASHIGUCHI, Takashi HONDA
Article type: Article
Session ID: 1469
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper describes the novel micro actuator using permanent magnet and magnetic fluid. The micro electromechanical actuator without the wire for supplying the energy is driven by the magnetic force produced by the alternating magnetic field. The micro actuator is composed of cylindrical neodymium magnet and kerosene-based magnetic fluid. The alternating magnetic field is generated by using of the Helmholtz coil and the bipolar power source. The actuator is the linearly displacement type actuator. The high-speed video camera system is used to measure the displacement of the actuator. It is found that the frequency of the reciprocating motion corresponds to the input frequency, and the amplitude of reciprocating motion has peak value for the input voltage.
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Kunio SHIMADA, Shigemitsu SHUCHI, Eiichiro YUZE, Shinichi KAMIYAMA
Article type: Article
Session ID: 1470
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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As a new intelligent or smart fluid, we propose an amorphous compound fluid (ACF). This fluid has nm size magnetite and mm size amorphous particles in a solvent. This report shows experimental data of viscosity of ACF in rotating rheometers of cone types under transverse magnetic field and those of magnetization under DC magnetic field. The experimental results are investigated with the aggregation as magnetic cluster confirmed by observation.
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Hideki KAWAI, Shingo KISHIKAWA, Hiroshige KIKURA, Masanori ARITOMO, Hi ...
Article type: Article
Session ID: 1501
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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It is known that rotating membrane filtration using a Taylor-Couette vortex flow (TCVF) system has an effect which reduces build-up of a cake layer on a surface of membrane filter. Although it is expected that the effect leads, for example to development of a new hemodialysis filter, fluid dynamic analysis is seldom performed. Here, TCVF is visualized by laser sheet device to study the fundamental vortex structure and then, by replacing the rigid inner cylinder with the filter, the particle-liquid separation through the inner rotating filter is performed with the TCVF. Supposing a future compact design, the aspect ratio, Γ (=H/d, H is the height of the device and d is the gap width between inner and outer cylinders) of the TCVF device is set up as small as about 3, which means that a vortex structure contacts with the upper or lower boundary-end is affected by the Ekman boundary layer.
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Kenji TSUTSUMI, Taichi YOSHIDA, Toshihiro KAWAGUCHI, Toshitsugu TANAKA ...
Article type: Article
Session ID: 1502
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper describes the measurement of particle behavior of inner structure by using MRI. Another way to measure inner structure is X-ray, but it is harmful to human body and can not measure velocity. We measured the radial and axial segregation of mixture of different size particle in a rotating cylinder. The effects of cylinder shape and particle size on segregation phenomena were studied. Furthermore, the particle velocity distribution was measured by the tagging method.
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Midori MIZUNO, Satoru TSUNO, Kuniomi ASAKURA
Article type: Article
Session ID: 1503
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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We simulated the motion of spherical particles in a rotating rectangle vessel filled with water using an Eulerian/Lagrangian method. The collisions between particles and between a particle and a wall was calculated by DEM. The DEM for particles with uniform diameter was improved for those with size distribution. The volumetric fraction of the sphere to grid of fluid was taken into account, because the particles were large (the mean diameter was 12.53mm). The roughness of the wall of the vessel and the surface of the particle was taken into account for simulation. A comparison of results obtained by simulation and experimental observations showed acceptable levels in solidliquid flows.
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Akira RINOSHIKA, Masami NAKANO
Article type: Article
Session ID: 1504
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In order to reveal unsteady features of gas-solid two-phase flow in both Fourier and physical spaces, the wavelet multi-resolution analysis, employed to analyze the experimental data of the wall pressure-time signal, were discussed for different wavelet bases. It is evident that the minimum-bandwidth discrete-time (MBDT) wavelet basis offers superior frequency-domain properties to Daubechies wavelets given a filter of the same length.
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Masahiro NISHIDA, Koichi TANAKA, Yukinori MATSUMOTO
Article type: Article
Session ID: 1505
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The dynamic behavior of mono-disperse particulate aggregation subjected to projectile impact at velocities less than 20 m/s was investigated experimentally. The particulate aggregation consists of mono-size nylon spheres arranged randomly in a rectangular parallelepiped container. A steel sphere struck, obliquely several nylon spheres on the top layer of the particulate aggregation. The motion of particulate aggregation and steel projectile was recorded by two high-speed video cameras (Redlake MASD, Motion Scope). In particular, the effects of the impact velocity, impact angle and diameter of steel projectile on the motion of steel projectile after impact were discussed in detail.
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Toshihiro SAWAMURA
Article type: Article
Session ID: 1506
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The investigations of the velocity distribution and the cutting capability on the abrasive water jet are carried out. The velocity of the water and the particle in abrasive water jet are measured by PIV and PTV, respectively. In this study, The red and blue flashes from stroboscopes are used for PIV and the jet photographs are taken. Then, the water velocity is obtained after the photographs are processed by PC. The weight distributions of the abrasive water jet are obtained by using the box with various size hole. The cutting capability distributions are obtained by combining the water and particles velocity distributions with the probability density distributions of the jet. As the Result, the peak of the cutting capability is shown not only at the center of the jet but also around the jet.
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Daisaku SAKAGUCHI, Carlo BAGNERA
Article type: Article
Session ID: 1507
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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DGV (Doppler Global Velocimetry) is a system to measure velocity of particles crossing a laser sheet, by analyzing the scattered doppler shifted frequency of a light sheet. The light frequency shift is very weak because of the very low speed of the particles compared to the speed of light. In order to overcome this problem, an absorption line of the molecular iodine is used: the absorption of iodine depends strongly on the light frequency going through the iodine vapor. By this mean, it is possible to measure the scattered light intensity going through the iodine and normalize it to the scattered light: this ratio gives us the percentage of light absorbed by the iodine and therefore the doppler shifted frequency can be traced back to particle velocity. In this paper, the measurement accuracy of DGV system was discussed from the point of view of the laser mono-mode stability.
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Teruyoshi YAMAZAKI, Masahiro TAKEI, Yoshifuru SAITO
Article type: Article
Session ID: 1508
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This study evaluates particle density distribution images in a pipe cross-section by means of 3D-wavelet transform that is a parameter to indicate the dominant transition among CT time frames. It is clarified that a time level 5 is the most particle density transition. Therefore, it is possible to evaluate density distribution of particle free fall.
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Hiroshi UEDA, Kiyoshi HORII
Article type: Article
Session ID: 1509
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The inspection system for pharmaceutical conveying pipeline using a spiral flow has been developed. It consists of a CCD camera attached to an optical fiber, a cloth parachute and a spiral flow nozzle. To obtain a spiral flow, pressurized air is forced into the nozzle. The parachute is able to keep its long distance inflation by spiral flow and pulls the camera for inspection of an inner wall's condition in small diameter pipelines.
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Junichiro MATSUSHITA, Noritaka KAKUTA, Hiroshige KIKURA, Masanori ARIT ...
Article type: Article
Session ID: 1510
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Thermal behavior of ferromagnetic particles in magnetic fluids were investigated using an optical micro-scope system. Real-time visualization of the Brownian motion of particles were carried out by using micro-scope and high speed camera on micro-capillary flow. The analysis of digital images with Particle Tracking Velocimetry (PTV) was applied to investigate the thermal behavior of ferromagnetic nano particles.
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Kuniomi ASAKURA, Midori MIZUNO
Article type: Article
Session ID: 1511
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The usefulness of a jig separator for classifying plastics in electric appliances is investigated. Although various types of jigs have been used for more than 100 years, little is still known about the precise mechanisms of jigging. Numerical simulation is conducted to obtain a better understanding of the jigging processes. The simulations give results that are very similar to those obtained by experiments. Two types of spheres with a difference in density of 10 kg/m^3 and the same diameters are classified. In addition, particles with the same settling velocity and different diameters are also classified. The jig separators found to be very sensitive to slight differences in terminal settling velocity and response time of the particles.
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Tomomasa UEMURA, Yasufumi YAMAMOTO, Noriyoshi YONEHARA, Manabu IGUCHI
Article type: Article
Session ID: 1512
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Generation of tiny droplets caused by surface tension force at gas-liquid and liquid-liquid interface are captured by high speed (500 frames per second) and high resolution (a square with 1024 pixels long) video cameras. When a air bubble rise up through an oil-water interface, three types of water droplets are generated in the oil layer. The sources of the droplets are revealed by using high speed video cameras. Surface tension force plays an important role to the phenomena. It connects entrained water with a rising bubble, drives a jet flow, and cause waves on the interface.
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Yoshihiko OISHI, Hiroshi FUKUDA, Yuishi MURAI, Yoshiaki KODAMA, Fujio ...
Article type: Article
Session ID: 1513
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Experiments were carried out to measure skin friction in a horizontal rectagular channel flow which contains various size of air bubbles. First of all, the relationship between the bubble motion and the temporal fluctuation of local skin friction is investigated experimentally at Re =l.lx10^4, in which approximate bubble size ranges from 3 to 30mm. The negative correlation between the local skin friction and the local void fraction is confirmed by simultaneous measurement of shear stress and interfacial visualization. It became clear that the local skin friction decreased in the rear region of large bubbles. Secondly, particle tracking velocimetry is applied to a bubbly two-phase flow to investigate the mechanism of turbulent shear stress modification. We measured three componential stresses with the PTV data at Re=2.0x10^4 and found that a role of the vertically correlated shear stress was important to reduce the total stress effectively.
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Jotaro NAGAO, Yuichi MURAI, Yasushi TAKEDA
Article type: Article
Session ID: 1514
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Frictional drag reduction in a horizontal turbulent boundary layer caused by bubbles is investigated experimentally using UVP (ultrasound velocity profiler). This paper presents the measurement principle for the channel flow and the average velocity profile, which alters in case of bubble mixture. The results indicated that we needed to introduce conditional averaging of the instantaneous velocity profile to distinguish the effect of bubbles.
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Hisanobu KAWASHIMA, Atuhide KITAGAWA, Koichi HISHIDA, Yoshiaki KODAMA
Article type: Article
Session ID: 1515
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The turbulent structure of microbubble flow in a horizontal channel is experimentally investigated using imaging techniques in order to clarify the mechanism for a drag reduction caused by microbubbles. A measurement system of both liquid phase and bubbles is proposed based on the combination of Particle Tracking Velocimetry, Laser Induced Fluorescence, and Infrared Shadow Technique (PTV/LIF/IST). The experimental results show that the Reynolds stress of liquid phase in microbubble flow becomes smaller than that in single-phase flow. The bubble deformation makes a Reynolds stress in liquid phase decrease.
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T. Nakatani, T. Kawamura
Article type: Article
Session ID: 1516
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Direct numerical simulations of shear and homogeneous turbulent flows containing a deformable bubble are carried out for investigating interactions between a bubble and turbulent eddies. Taking the spatial average of second invariant of velocity gradient tensor Q, the values near the bubble are negative in both homogeneous and shear flow, though the values at other points are nearly zero. It indicates that vortex near the bubble is prevented to generate by the presence of the bubble. As the result, production term of turbulent energy in shear flow reduces compared with the case without a bubble.
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Kazuyuki TAKASE, Hiroyuki YOSHIDA, Hidesada TAMAI, Yasuo OSE
Article type: Article
Session ID: 1517
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In order to predict the water-vapor two-phase flow structure in a fuel bundle of an advanced light water reactor, a large-scale numerical simulation was carried out using a newly developed two-phase flow analysis code and a highly parallel vector supercomputer. Conventional analysis methods such as subchannel codes need composition equations based on the experimental data. In case that there are no experimental data for the advanced light water reactor, therefore, it is difficult to obtain high prediction accuracy. Then, a new analysis method using the large-scale direct numerical simulation of water-vapor two-phase flow was proposed. This paper, describes the predicted results of a large-scale bubbly flow in a narrow square duct. Regarding the mechanism of bubble coalescence and fragmentation the useful knowledge was obtained.
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Toshio SASAKI, Ichiro KURODA, Niro NAGAI, Yuichi MURAI, Fujio YAMAMOTO
Article type: Article
Session ID: 1518
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Alkaline water electrolysis is the one of technologies of hydrogen production through decomposition of water by an electric power. The present study aims at improvement of hydrogen production in 'water electrolysis from viewpoint of generated bubbles' behavior, which interrupts the electric current between two electrodes. The measurement of electric current and the visualization of bubbly flow are practiced simultaneously to discuss the influence of the two-phase flow structure onto the water electrolysis. The paper describes two experiments on the micro-channel water electrolysis and on the water electrolysis by use of vibrating electrodes.
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Shigeru MURATA, Takahiro YAMAGUCHI
Article type: Article
Session ID: 1519
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper presents the measurement results of air bubbles rising in a cubic cavity with digital holography. The air bubbles in water are illuminated with He-Ne laser light and the resulting interference fringes are recorded with a high-speed CMOS camera to analyze them on a digital computer based on wave optics. Full-volume digital holography is employed for the detection of bubble position in 3D space. The bubble position in depth is estimated by taking the position of bubble image where the horizontal gradient averaged in a local area on the boundary of bubble image has the maximum value along the axis of depth. The experimental results show that the present technique successfully express the motion of rising air bubbles generated from a nozzle at the bottom of the cavity.
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Fumio SHIMIZU, Katsuya NAGAYAMA, Kazuhiro TANAKA
Article type: Article
Session ID: 1520
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In the ordinary PIV measurement, digital images are gotten from scattering light of tracer particles and moving distance of the particles is measured. When the PIV is applied to the gas/liquid two-phase flow which has high void ratio, however, the velocity measurement is very difficult because the scattering light from the gas/liquid interface is strong compared with from the particles. The one of important factors is the luminance adjustment of the scattering light in the PIV measurement of gas/liquid two-phase flow. In the present study, the information of high-level luminance is utilized actively to measure the moving velocity of the gas/liquid interface. By the adjustment of the contrast and the brightness of original digital images obtained from the PIV measurement, the information of the high-level luminance is extracted and the shape of the gas/liquid interface can be distinguished. As the large-scale deformation and high-speed movement are included in the motion of the interface, high resolution in both time and space has to be required to get the digital images. By the utilization of the high-speed camera and the luminance adjustment, the measurement of the moving velocity of the gas/liquid interface was succeeded.
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Yuichi MURAI, Shin-ichi TODA, Fujio YAMAMOTO
Article type: Article
Session ID: 1521
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Helical coil type heat exchanger tubes are used in the evaporator and the superheater of the prototype fast-breeder reactor (FBR) Monju. The present study visualizes the flow pattern of gas-liquid two-phase flow in the helical tubes to clarify the influence of centrifugal acceleration due to the curvature. The three-dimensional interfacial structure is measured using CT from the backlight projection image acquired in six directions at a local section. The results have shown that the interfacial structure became asymmetric in the case of high Ga number, oiwing to combination of gravity and centrifugal acceleration.
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N. Fuangworawong, W. Wangjiraniran, H. Muragawa, H. Kikura, M. Aritomi
Article type: Article
Session ID: 1523
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The objective of this work is to investigate local void fraction behaviors in countercurrent air-water bubbly flow. Local void fraction of vertical air-water flow in a round tube with inner diameter 50 mm is measured by using Wire Mesh Tomography (WMT). Radial void fraction patterns are visualized and discussed in this work.
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Kaoru YAMAGUCHI, Masafumi HANAZAWA, Takaaki SHIZAWA, Takashi NAGUMO, S ...
Article type: Article
Session ID: 1601
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Turbulent mixing of a circular jet, which is commonly used in many gas turbine applications, has been studied from the viewpoint of control. The static pressure fluctuation is a basic flow parameter in turbulence. In this study, the vortex structure of the free shear layer in the circular jet is excited by the piezo film actuators. The effect of axial excitation on the turbulent mixing is clarified by simultaneous measurement using hot wire anemometer and static pressure probe.
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Takashi NAITOH, Chieko YAMAMOTO
Article type: Article
Session ID: 1602
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Zero-net-mass-flux (Synthetic) jets are produced by the back-and-forth motion of a piston. Synthetic jet flow experiments using PFV were conducted to characterize the flow. Phase-averaged vorticity fields, which are synchronized with the movement of the piston, have been calculated from velocity vector fields. Jet flow patterns are classified into four different categories. These four categories are identified from the iso-vorticity contours and fluorescence dye flow visualization images, and the classification of the patterns is shown in the Reynolds number versus Strouhal number plot. Three different categories, Flat type, Ramp type, and Sine type, where the mean velocity through the orifice was varied with respect to time are investigated. It is found that the Sine type velocity variation is proper to produce the flow pattern of "laminar vortex rings."
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Kohei HODOYA, Noriamsa MIYAGI, Motoaki KIMURA
Article type: Article
Session ID: 1603
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Active control of jet is applied at control of burner flame or air-conditioning. In this study, secondary film flow is built on the outside of axisymmetric jet. And it is driven by the acoustic excitation for active jet control. Furthermore, the velocity ratios of mainstream and film flow and acoustic strouhal number were changed. The quantitative velocities were measured by the LDV and jets were visualized by LLS for research of change in jet structure. As a result, axisymmetric jet is diffused in all condition by acoustic excitation vortices. In the case of VR=0.5, potential core is shortened by St=0.6. At VR=1.0 diffuses than at VR=0.5. Potential core is most short at VR=1.0, St=0.6. Mainstream most mixes with film flow at VR=1.0, St=0.6 and film flow mixes with surrounding air at VR=1.0, St=0.3.
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Masashi NISHIDA, Masahiro NAKASHIMA, Takahide TABATA, Yasuyuki SHII, T ...
Article type: Article
Session ID: 1604
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The diffusion of the jet issuing from the pipe with the fluttering fins has been studied by using the method of the flow visualization, the PIV, and the wavelet analysis. The velocity distribution of the jet with the fluttering fins has been measured and the jet widths have been obtained, comparing with that without ones. As a result, it has been clarified that the jet with the fluttering fins diffuses largely under the influence of the fins. Furthermore, the velocity fluctuations of these jets with and without fins have been also investigated by using the hot-film sensor and the anemometer. The wavelet analysis on these fluctuations has been conducted. The structure of the jet has been also discussed by using the results of this analysis. As a result, it has been found that there exists the difference of the middle scale structure between the jets with and without fluttering fins.
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Yuuta NAKANO, Masahiro NAKASHIMA, Takahide TABATA, Yasuyuki SHII, Tsut ...
Article type: Article
Session ID: 1605
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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As a part of the study on the control of the jet diffusion, the jet issuing from the circular pipes having the inclined section has been investigated. By using the flow visualization and PIV method, the velocity distributions have been measured and the jet widths have been also obtained from these distributions. As a result, it has been clarified that the velocity distributions at the downstream location near the exit of the pipes show to be unique and they are similar to those of the ordinary circular free jet at the location far from the exit. Moreover, it has been found that the width of the jet issuing from the pipes with the inclined section becomes large, comparing those of the jet from the pipes with normal section and the ordinary circular free jet.
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Shigetaka FUJITA, Takashi HARIMA, Keisuke MORITA, Hideo OSAKA
Article type: Article
Session ID: 1606
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The flowfield of the three-dimensional jet issuing from a rectangular nozzle (aspect ratio: AR=12.5) with a rectangular notch (AR=2.5, 7.5 and 12.5) at the midspan were examined experimentally. The aim of this study is to examine the control of the mixing and diffusion processes of the flowfield of a rectangular jet using a rectangular notch. Measurements were made using an X-type hot-wire prove, linearized constant temperature anemometers and a five holes pitot static pressure tube. In this experiment, the Reynolds number was kept constant 30000 (notch AR=2.5 and 7.5) and 15000 (notch AR=12.5). From the results, the followings were clarified. The potential core length for the case of notch AR=12.5 took the maximum value in all notch AR. Furthermore, the entrainment rate showed the maximum value for the case of notch AR=12.5.
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Tasuku HORI, Yuusuke TAKISAWA, Nobuo OGAWA
Article type: Article
Session ID: 1607
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The flow fields of the jets into counterflowing uniform flow include regions of large diffusion. Investigating of the flow field is important to know the diffusion phenomenon. And the results are useful to discuss the fields of combustion, mixing, and so on. Recently we found that there is mixing layer structure and no re-circulating zone. In this paper, this flow field is divided into three groups, flattering, puffing and attached flow, depend on the vortex pattern. The field is investigated by the measurements of the velocity, static pressure, and visualization.
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Koichi TSUJIMOTO, Toshihiko SHAKOUCHI, Shuji SASAZAKI
Article type: Article
Session ID: 1608
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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To develop the efficient method of jet mixing, direct numerical simulations of two inclined jets are carried out. After the jets collide with each other, it expands perpendicular direction to the plane on which two jets exist, and turbulence intensity is largely enhanced compared to that of the single round jet. Then in order to investigate the mechanism of collision of jets, Snap-shot POD (Proper Orthogonal Decomposition) is applied. It demonstrates that the large scale mode behaves like vortex rings on the plane through at the center of two jets, that is, the collision of jets means that the generation of such a large-scale structure take place in mixing.
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Toshihiko SHAKOUCHI, Tsuyoshi TANABE, Koichi TSUJIMOTO, Hirokazu OGAWA
Article type: Article
Session ID: 1609
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Impinging jet has an excellent heat transfer characteristics at and around the stagnation point. In this study, the effects of interaction between two round jets impinging on a flat plate with a small spacing on the flow and heat transfer characteristics are investigated experimentally. It is shown that the heat transfer on the plate between the two jets can be improved considerably and the operating power of the nozzle-plate system decreases comparing with the single jet.
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Hideharu MAKITA, Takeru MORITA, Nobumasa SEKISHITA
Article type: Article
Session ID: 1610
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Effects of rib structures on vortex pairing were investigated in a bimodally excited parabolic plane jet. To control the peak-valley structure of the vortex tube, small half-cylindrical tabs were attached to the flat plates perpendicularly settled to the jet exhaust just beside the jet exhaust. Knee points appeared regularly at the valleys of the wavy vortex tubes just downstream of each tab. As the wavy tubes developed downstream, ribs, or small longitudinal vortices, elongated from the knee points of the upstream weaker vortex connected it to the downstream stronger vortex at its valleys or peaks. The ribs winded up the upstream vortex toward the downstream one.
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Jun AKAZAWA, Hayato MORI, Kuniaki TOYODA, Riho HIRAMOTO
Article type: Article
Session ID: 1611
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The relation of the vortical structure and the entrainment in the initial region of a plane jet was investigated under the four conditions of vortex generators by vorticity measurements. The vortices were enhanced and stabilized by streamwise and spanwise disturbances. The three-dimensional views of the vortices were constructed by applying the Taylor hypothesis to the phase-average vorticities, and the entrainment was discussed in relation to the vertical structures. The result reveals the enlargement of entrainment by the interaction of spanwise and streamwise vortices
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Yukihiro SAWADA, Hiroaki HASEGAWA, Kazuo MATSUUCHI
Article type: Article
Session ID: 1612
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Flow separation causes large energy losses in a fluid machinery and stall on airfoils. Longitudinal vortices are produced by the interaction between jets and a freestream. The vortex generator jet method is an active control of flow separation and can achieve the adaptive control by properly adjusting the jet speed. In the previous study, it was confirmed that the triangular orifice generates the strong vortex and makes effective the pressure recovery in the diffuser for the three types of the jet orifice (circular, triangular, and square). In this study, the effect of the direction of the vertex of the triangular orifice on separation control is investigated. It is concluded that the Model-U (the vertex sets in the upstream direction) makes effective separation control in comparison with the other models.
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Junko ODA, Hiroshi IWAKIRI, Shigehira OZONO
Article type: Article
Session ID: 1613
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The wake behind a circular cylinder (diameter d) with a long splitter plate inserted is investigated experimentally in a water tank at Re=1.12×10^4. The splitter plate is traversed at three levels (Z/d=0, 0.5, 1.0). As the splitter plate is shifted upstream horizontally, the base suction coefficient increased gradually, but it falls critically at a certain position depending on Z/d. To make clear the mechanism of the critical change, PIV measurements are conducted for pre- and post-critical regime. It is found that the stream pattern changes depending on level Z.
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Masanori MATSUMURA, Kazuhiro NAGATANIN
Article type: Article
Session ID: 1614
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Turbulence characteristics in the wake of a two-dimensional body with a splitter plate were investigated. The effect that a splitter plate can reduce the periodic vortex shedding has already been known, however, another effect of a splitter plate is not known in detail. Then, a splitter plate was used in order to control Reynolds shearing stress in this study. As the resalt of this study, it was found that there are optimum combinations of location and width of a splitter plate for the reduction of periodic vortex shedding and the increase of Reynolds shearing stress.
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