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Junji OKAMURA, Kenkichi OHBA, Takayuki YAMAKAWA
Article type: Article
Session ID: 1346
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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By using an electro-rhydrodynamic (EHD) spraying technique, the droplets of micrometers size can be obtained through the disintegration of column of liquid subjected to the electric field between needle and plate. The EHD spraying exhibits various modes depending on electric field strength, mass flow rate and properties of liquid. In this work, the spray process in the tip of a needle was observed using high-speed video camera. In order to investigate the mechanism of spraying in the cone-jet mode, the volume and length of meniscus were measured from the pictures. As a result, it was found, that vibration and disintegration of meniscus took place depending on the change in the electric field strength and the mass flow rate.
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Seiji SHIMIZU, Takatoshi NISHIYAMA, Motohiko NOHMI, Akira GOTO, Tatsuy ...
Article type: Article
Session ID: 1347
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A micro abrasive water jet system is constructed as a trial. The constructed system is an abrasive water suspension jet type. The a nozzle diameter is 50 to 100 μm and the maximum jetting pressure of the system is 21 MPa. Experiments are conducted to clarify the flow structure of the jet. Cutting tests are carried out with specimens of copper plate. A compact slurry jet is formed by the constructed system. It is possible to cut a copper plate with a cutting width slightly larger than the jet diameter.
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Takao FUJITA, Keizo WATANABE
Article type: Article
Session ID: 1348
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The purpose of this study is to clarify the effects of a gas-liquid interface on a hydrophobic sphere surface. The flow patterns past the sphere were numerically simulated by applying a wet boundary condition for fluid slip. The simulation results of the hydrophobic surface sphere showed that the Vortex Loop was not exist at Re < 400 and the Vortex Tube was exist at Re > 400. The flow patterns agreed with those of the flow visualization results.
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Yasuo KOIZUMI, Hiroyasu OHTAKE, Hiroki TAKAHASHI
Article type: Article
Session ID: 1349
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The friction characteristics of water in a sub-millimeter scale channel were investigated experimentally. The friction factors and the critical Reynolds number were measured using water flow through circular tubes and rectangular channels. The experimental results show that the measured friction factor for water agreed well with the conventional Poiseuille (λ=64/Re) and Blasius (λ=0.316 Re^<-0.25>) equations in laminar and turbulent flow regime.
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Kensuke KANDA, Ming YANG
Article type: Article
Session ID: 1350
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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To investigate the relation between nano scopic surface interaction and whole flow behavior for the bio-fluid flow in micro tubes with various surface properties, lateral force, absorption, and pressure drop measurements were carried out. The results of pressure drop measurement showed the reduction of the friction factor dependent on surface property and the concentration of the bio-molecules. The tendency of the measured frictional force corresponds to the molecular absorption on the surface. It is concluded that the whole flow behavior relates to the surface phenomenon in micro flow of bio-fluids.
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Yasuo KOIZUMI, Hiroyasu OHTAKE, Tomoyasu TSUYUKI
Article type: Article
Session ID: 1351
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Characteristics of a fluidics device of 1×1 mm flow area was examined using water as test fluid. The fluidics device had a simple geometry of y shape with two signal ports. Although Reynolds number tested was low; about 1000, the device functioned as the fluidics device; flow provided for a signal port flowed out from an opposite outlet. A fluidics device where the signal ports were replaced with dead-end boxes which had a piezo elements on the wall. It was expected that the piezo elements created a micro jet with no net flow rate. As the frequency of the piezo element actuation was increased, a delivery flow rate from the opposing outlet increased and a delivery flow rate from the other outlet decreased by that amount. It was confirmed that the micro/mini flow device with the piezo element would have a possibility to work as the flow control device.
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Makoto KIDERA, Kenta TOH, Hiroshi TSUKAMOTO, Koji MIYAZAKI
Article type: Article
Session ID: 1352
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Numerical simulations are conducted to investigate the mechanisms of developed valve-less micro-pumps by using commercial software CFX-5. In the numerical simulations unsteady vortexes are observed at the jucntion. The vortexes work as the dynamic valve of the micro-pump. We also observed micro-pump and conducted PIV analysis in order to confirm the validity of numerical simulations. PIV results agreed well with the simulation results.
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Nobuko Seino, Masaki Shinoda, Masatsugu Tomotaka, Kensuke Kanda, Tomoy ...
Article type: Article
Session ID: 1353
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A design approach of valve-less diffuser micropump driven by piezoelectric element (PZT) was developed, with the result that a flow rate of 210 μL/min and maximum pressure of 37kPa were achieved. In addition, we showed the effect of the viscosity and the cross-section areas of before/after chamber on the PZT displacement magnitude performance. These results were utilized for the pump development to equalize the flow rate of solutions with different viscosity. The pump has high potential for application of bio-and chemical micro analysis system.
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Noritomo YAMAGUCHI, Tomoyuki OZAWA, Kensuke KANDA, Ming YANG, Nobuko S ...
Article type: Article
Session ID: 1354
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In this research, it aims to improve the transporting efficiency of diffuser pump by serial connecting the pumps and using elastic material as a buffer. A Si-based diffuser pump with two serially connected of chambers and diaphragm, and a silicone tube between two chambers was developed and evaluated. This system showed high transporting efficiency by using the effects of phase shift and resonating elastic materials.
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Motoya KANETA, Souichi SAEKI, Takashi SAITO
Article type: Article
Session ID: 1355
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper presents a novel pH measurement technique for microfluidics devices, "2-Color Laser Induced Fluorescence". In this technique, an undesirable influence of excitation light distribution can be eliminated by dividing one fluorescence, image with the other one taken at the same time. This can simplify measurement procedure in terms of omitting fluorescence intensity normalisation at each pixel, and could measure a sealer distribution more accurately than 1-color LIF. In this study, the proposed method was applied to neutralization chemical reaction in T-type microchannel. Using Fluorescein and Rhodarnine-B, the divided value of fluorescence intensities was calibrated with 7 points of pH. Spatial intensity error can be reduced to about 80 to 90% as compared with 1-color LIF. As a result, pH distibution of neutralization reaction between acetic acid and ammonia at T-junction .was visualized quantitatively at some flow rate conditions.
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Kyosuke SHINOHARA, Yasuhiko SUGII, Arata AOTA, Akihide HIBARA, Takehik ...
Article type: Article
Session ID: 1356
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper reports a new technique of micro-resolution Particle Image Velocimetry (PIV). To investigate transient vortices at oil-water interface in a microfluidic device, a high-speed micro-PIV technique was developed by combining a high-speed camera and a continuous wave (CW) laser. The technique was applied to a micro counter-current flow. The micro counter-current flow was an efficient solvent extraction system consisting of water flow and butyl acetate flow. The velocity fields of water in the micro counter-current flow were visualized for a time resolution of 500 μs and a spatial resolution of 2.2 x 2.2 μm. Using the high-speed micro PIV technique, the vortices at the water-butyl acetate interface were captured clearly.
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Osamu HAMANAKA, Hiroharu KATO
Article type: Article
Session ID: 1358
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This research studies on the acceleration mixture and chemical reaction of two reacting fluids by using special structure in a micro-fluidic device. By using this structure, the flow of two reacting fluids becomes four layers and the reaction speed becomes faster than usual two-layer flow. The typical flow channel width of a micro-fluidic device is 40 to 80 μm. This size is not easy to fabricate or to visualize the flow. First, we experiment with the flow channel 10 times as large as the actual device to overcome these difficulties. Paints were used as the visualization method of the flow. The experimental result showed that in order to increase mixture and chemical reaction at high velocity, the number of layers increases further and mixing speed must be faster. For that purpose, the structure of flow channel is a problem. In order to solve the problem, the analysis and the simulation in CFD performed.
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Ken NISHIKAWA, Yoshifumi OGAMI
Article type: Article
Session ID: 1359
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Effective mixing is an important task in micro-fluidics for chemical and biochemical applications. Because, of the small scales, flow regime in small device is predominantly laminar, so the efficient mixing obtained in turbulent flows is not practically attainable. In order to promote the convective mixing performance in these systems, macro-scale mixing technique such as mechanical stirring is necessary. A shuttlecock optical micro-rotor, which rotates in fluids and stirs the fluids in such micro scale systems, is introduced for this purpose. To investigate the rotor's mixing performance in the flow fields, CFD technique is used in this paper. The results indicate that optical micro-rotor has more effect on the mixing. In this way, convection occurs to enhance the mixing. The mixing efficiency is calculated on the outlet of the flow field. It is found that the mixing efficiency can be enhanced by increasing rotation speed.
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Manabu TAKAO, Toshiaki SETOGUCHI, Kenji KANEKO
Article type: Article
Session ID: 1401
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Two types of turbines using pitch-controlled blades for wave energy conversion have been proposed so far. The paper shows the comparison of the performances of these turbines from the viewpoints of the starting and running characteristics. Experimental investigations have been performed by model testing of a turbine rotor with fixed blades under steady floe conditions. Then, the running and starting characteristics under irregular flow conditions have been obtained by a computer simulation using a quasi-steady analysis.
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Manabu TAKAO, Takuya IWATA, Yoshihiro FUJIOKA, Toshiaki SETOGUCHI
Article type: Article
Session ID: 1402
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In order to develop a high performance radial turbine for wave energy conversion, a radial turbine with pitch-controlled guide vanes has been proposed and investigated experimentally by model testing. The experiment has been carried out under steady flow conditions. Then, the results have been compared with those of a radial turbine with fixed guide vanes by previous studies. As a result, the performances of the presented radial turbine under steady flow conditions have been clarified. Furthermore, it seems that the presented radial turbine is superior to the conventional radial turbine.
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Masami SUZUKI, Chuichi ARAKAWA
Article type: Article
Session ID: 1403
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Experimental investigations on the effect of the guide vanes on the performance of Wells turbine are reported. The primary effects of that are only increase of the efficiency but also the postponement of the stall, increase of the minimum torque and the starting torque at attack angle of 90 degrees. In the several factors on the performance of the guide vanes, the axial spacing between the rotor and the guide vanes has great influence.
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Masami SUZUKI, Chuichi ARAKAWA
Article type: Article
Session ID: 1404
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The wave power generating system using the Wells turbine is installed in the breakwater in Sakata port, Japan, and consists of the air chamber, turbine, generator and safety devices. The purposes of this paper are to reveal the characteristics of each component in this system with the experimental data in the real sea, and to evaluate the accuracy of numerical models used in the simulation. As for the motion of water in the air chamber, the eigenfunction expansion method is introduced, and the wave height measured 275m away from the chamber is employed for the input of the simulation.
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Takashi HISAMURA, Sho OZAKI, Toshiaki KANEMOTO, Daisuke TANAKA, Naoki ...
Article type: Article
Session ID: 1405
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The counter-rotating type hydroelectric unit which is composed of the tandem runners and the generator with the double rotors has been proposed by the authors. This unit is applicable to the micro hydropower in coexisting with the natural ecosystem, because the unit can be easily moored with one cable to mountain torrents and/or rivers without the civil construction on a large scale. This paper discusses the effect of the runner profiles on the performance and the internal flow conditions.
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Daisuke TANAKA, Toshiaki KANEMOTO, Yayoi YONAYAMA
Article type: Article
Session ID: 1406
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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To cope with the warming global environments, greenhouse gas emission should be reduced in the electric power generation. The hydroelectric power should occupy the attention of the electric power generation systems, as clean and cool energy source with the highest density. The authors have proposed the counter-rotating type hydroelectric unit. This unit is applicable to the micro hydropower to coexist with the natural ecosystem, because the unit can be easily moored with one cable in rivers and/or mountain torrents without a large-scale construction. This paper discusses the performances in the cavitating conditions. The hydraulic performances and the flow condition of counter-rotating runners with the numerical analysis are also discussed.
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Akira INAGAKI, Toshiaki KANEMOTO, Yayoi YONAYAMA, Naotoshi MARUYAMA
Article type: Article
Session ID: 1407
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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We are under obligation to coexist with natural ecosystem, for the next leap in hydroelectric power developments. In such circumstances, this paper proposes a new type hydraulic turbine, named "Gyro-Type Hydraulic Turbine", accompanying with the flow visualizations by PIV and the numerical simulations by CFD around the blades in the rotating conditions. At low rotational speed, the most of the rotational torque is generated by the lift force of the blade facing to the upstream. On the other hand, at high rotational speed, the torque comes to be caused by the lift force of the blade not only facing to the upstream but also facing to the downstream.
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Hiroaki KINOSHITA, Akira INAGAKI, Kunio HASHIGUCHI, Toshiaki KANEMOTO
Article type: Article
Session ID: 1408
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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To conserve natural ecosystem and coexist with nature, a new type hydraulic turbine, named "Gyro Type Hydraulic Turbine", has been proposed by the authors. The turbine is suitable for shallow streams with high velocity in mountain torrents and/or rivers, and the rotor works and the fundamental characteristics have been discussed. Continuously, in this report, the effects of the stream velocity and the rotor profile on the performances are discussed with the experimental results.
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Takao MAEDA, Yasunari KAMADA, Yusaku SAKAI, Kotaro SUGI
Article type: Article
Session ID: 1409
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper shows the wind tunnel study of pressure distribution on a rotor blade of horizontal axis wind turbine. Comparison of the pressure distribution of rotational and static situation for the tip and root regions of the blade. The pressure distribution at tip region coincides for rotational and static situation. The pressure distribution at root region shows much difference for rotational and static situation. Especially for low tip speed, the normal force coefficient at root region shows larger value than those for the static situation.
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Oliver FLEIG, Makoto IIDA, Chuichi ARAKAWA
Article type: Article
Session ID: 1410
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The purpose of this research is to investigate the physical mechanisms associated with broadband tip vortex noise caused by rotating wind turbines. The flow and acoustic field around a wind turbine blade is simulated using compressible Large-Eddy simulation and direct noise simulation, with emphasis on the blade tip region. The far field aerodynamic noise is modeled using acoustic analogy. Aerodynamic performance and acoustic emissions are predicted for the actual tip shape and an ogee type tip shape. For the ogee type tip shape the sound pressure level decreases by 5 dB for frequencies above 3 kHz. No difference is observed in the overall aerodynamic performance of the wind turbine blade.
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Masaru Takahashi, Makoto IIDA, Chuichi ARAKAWA
Article type: Article
Session ID: 1411
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This study is aimed to investigate the physical structure of wake flow with Wind Turbine Blade. The wake flow field around WINDMELIII developed by AIST is simulated using compressible Large-Eddy Simulation. Vorticity and Velocity loss are predicted around the wind turbine blade. For the vorticity distribution, there are strongly region not only near blade, but also interference region in wake.
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Shinya HOTTA, Yutaka HASEGAWA, Hiroshi IMAMURA, Naoyuki YONEZAWA, Juns ...
Article type: Article
Session ID: 1412
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Horizontal Axis Wind Turbines (HAWT) are installed under the natural wind conditions, and they suffer complicated aerodynamic loads on the rotor blades due to turbulence, yawed inflow, and wind shear. This paper describes the results for such complicated loads on the rotor blade obtained by using a numerical method, which is composed of a load calculation model and a turblent wind field model. The former adopts an inviscid model based on the asymptotic acceleration potential method. The turbulent wind field is simulated with Veers model, based on a Fourier synthesis method.
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Yuko SATO, Tetsuya KAWAMURA
Article type: Article
Session ID: 1413
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Two-dimensional flows around a wind turbine of cross-flow are investigated by the numerical simulation. Incompressible Navier-Stokes equation is used for this simulation. A rotating coordinate system, which rotates at the same speed of the turbine, is used in order to simplify the boundary conditions on the blades of the turbine. Additionally, a boundary fitted coordinate system is employed in order to express the shape of the blades precisely. The third order upwind scheme is chosen for the approximation of the non-linear terms. Numerical simulations are also carried out by changing their shapes and angle of attack in order to estimate these effects on the performance of this turbine.
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Akisato MIZUNO, Aika SHIBUYA
Article type: Article
Session ID: 1414
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The authors developed the performance estimation method for Straight Wings Vertical-Axis Wind Turbines by means of two-stage actuator disk concept. In the procedure, power loss was taken into account. The present work is aimed at the evaluation of the dependency of performance on solidity. The result showed that it gave slightly better performance in comparison to single stage theory. The highest performance is obtained at a solidity of 0.08.
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Akisato MIZUNO, Akiyoshi IIDA, Keiko FUKUDOME
Article type: Article
Session ID: 1415
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In order to improve the aerodynamic performance of vertical axis wind turbines (VAWT), effects of pitch angle of rotor blades were numerically investigated. To solve the complicated turbulent flow field around moving airfoils with small computers, discreet vortex methods were utilized. The numerical result shows that the pitch angle is important factor to improve the aerodynamic performance. In the case of pitch angle is 1 degree, an angle of attack becomes small at upwind position of the rotor blade, and therefore, flow separation is restrained at upwind part of the VAWT. As a result, the power coefficient is 10 % larger than that of the conventional (pitch angel is 0 degree) VAWT.
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Yukihiro Nishimura, Haruo SAKAMOTO, Satoshi Tamai, Toshifumi Asai
Article type: Article
Session ID: 1416
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In our study, we set an aim that we set up a small wind power generator on the top of a building. When installing on the top of a building, there are few advantages. One, it do not cause much the damage to the environment around it as opposed to other wind power generator. Other, because wind is stronger, it is good for wind power generator the top of building. The purpose of our study is leading the design indicator of the optimal internal structure in the small wind power generator installed on the top of building. Therefore, we did two experiments. First, we did the magnetic analysis. Second, we did the experiment of generation of electricity. And, we consider the design indicator of the optimal internal structure in the small wind power generator by comparing these two experiment results. Moreover, the objective generation quantity of the designed generator was set as 5 kilowatt.
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Takahiro KIWATA, Issac GUTIERREZ, Atsushi OKAJIMA, Shigeo KIMURA, Hisa ...
Article type: Article
Session ID: 1417
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Our aim is to get basic data to increase the efficiency of micro horizontal axis wind turbine (HAWT) systems. The experiments were carried out in an open type wind tunnel. We measured the turbine performance of five-bladed wind turbines with MEL002 and MEL081 airfoil cross-sections. Flow characteristics of rotating blades of the turbine were observed using the oil-film visualization technique. Flow visualization allowed the identification of laminar flow, laminar separation bubble formation, flow reattachment, turbulent boundary layer, and turbulent separation. The complex patterns on the rotating blade surface were confirmed and identified by the oil-film visualization method. The performance of the wind turbine with MEL081 airfoil section was better than the other airfoil sections at low wind speed.
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Kenzo CHO, Yoshiaki TANZAWA, Takao SATO, Takumi HASHIZUME
Article type: Article
Session ID: 1418
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Many birds increase by flapping the wing and the whole wing is flexibly moved this time. This movement produces a difference in the air resistance. The air is grasped enough, when the wing is moved in the downward direction. The air is released from the clearance of the wing, when the wing is moved upward. It is considered to apply this mechanism to the bird type wing of the wind turbine. In the paper, the Three Sheet-Wing Vertical Long Model is investigated experimentally. The effect of the vertical long type and the importance of the catching boards and the outer wings are clarified.
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Toshiaki KANEMOTO, Masaki TONDA, Yosuke TSUDA, Yuki FUKUOKA
Article type: Article
Session ID: 1419
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper proposes the unique wind turbine system, which is composed of the tandem wind rotors and the peculiar generator with the inner and the outer rotors, and discusses the wonderful advantages of the system. The large-sized front wind rotor and the small-sized rear wind rotor drive respectively the inner and the outer rotors of the generator, in keeping the rotational torque counter-balancing. Such operating conditions enable to make the cut-in wind speed slower and to keep the frequency/output constant irrespective of the wind speed, without the conventional breaking and/or the pitch control mechanism.
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Masahiro Ueda, Yuusuke Sugita, Masahiro INOUE, Masato FURUKAWA, Yuuji ...
Article type: Article
Session ID: 1420
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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It is found that a brimmed diffuser accelerate the wind into the turbine, and a wind turbine with brimmed diffuser can produce more power than turbine only. Recently we research turbine blade for brimmed diffuser, and we found that the blade using thick airfoil at blade root (named NT-blade) can make good match for our brimmed difiuser. In this paper we compare NT-blade and normal blade using only NACA63 airfoil (named N-blade), and discuss it.
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Daisaku Tanimoto, Haruo Sakamoto, Masahiro Hanai
Article type: Article
Session ID: 1421
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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FRP blades used for wind power generators occasionally suffer from damages by lightning, and the expenditure and absence fee for blade replacement are tremendous. In this research to obtain the method for lightning protection, aluminum coating was applied. From the results using GFRP test pieces, 1/2 size blade models and the real blades were prepared as specimens with and without aluminum coating, and the effective results of aluminum coated blade on lightning damages were obtained. Aluminum coated blades showed little damage since lightning current is distributed by aluminum and so the lightning energy on the specimen. If the blade specimen is no aluminum coated, the lightning current can go into blades. This causes the blade failure. This failure morphology is close to the blade damage for the wind power generator in Iwate Inaba. However, the experimental condition needs to be considered in near future to obtain the closer blade failure.
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Takeshi SHIGEMOTO, Yutaka HASEGAWA, Koji KIKUYAMA, Masahiro TAGUCHI, K ...
Article type: Article
Session ID: 1422
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper describes the results of the performance analysis on a small WTGS (wind turbine generator system) installed above a building, which recently attracts attention as a local power station. The effect of the turbine location above the building and the neighboring buildings on the power output has been examined by a series of detailed field test and the numerical analysis based on the turbulent flow model. Using a conditional sampling technique the measurement results has been analyzed carefully, and examined the optimum location for the installation of the small WTGS above the building in relation to the building's height.
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Akinori KUWAYAMA, Yutaka HASEGAWA, Hiroshi IMAMURA, Koji KIKUYAMA, Yuk ...
Article type: Article
Session ID: 1423
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The purpose of this study is to investigate characteristics of flow over complex terrain and establish a wind prediction system for complex terrain, especially focused on the effect of hill height relative to boundary layer thickness. Wind tunnel experiments have been carried out to measure the mean velocity and turbulence characteristics of flow over 2-dimensional hills. The results from numerical analysis using k-ε model were compared with the wind tunnel experiments. After the verification of the numerical analysis, we have examined large impacts of the hill height relative to boundary layer thickness on the wind energy resources and the turbulence characteristics around hill.
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Takako KAWAMITSU, Shiro TAMAKI, Hiroshi NAGAI
Article type: Article
Session ID: 1424
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Since the Okinawa islands are surrounded by the sea in all directions, the source of supply of electric power in the distant islands are mainly diesel electricity power. Therefore, an electric power of unit price is expensive than coal thermal power generation. The electric power generation system by wind energy has an extreme advantage in the viewpoint of clean energy. In this research, we investigate the possibility of installing in the offshore-type wind turbine system. Furthermore, the effect of the amount of carbon dioxide reduction are evaluated
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Win Shwe Maw, Shingo FUJIWARA, Tsutomu TAKAHASHI, Masataka SHIRAKASHI
Article type: Article
Session ID: 1444
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The Hele-Shaw flows of a Newtonian fluid have been used to reproduce the flow patterns of two-dimensional potential flow. In the earlier papers, the present authors showed effects of elasticity on Hele-Shaw flows around a circular and a square cylinder, and a flow passing through a slit, and presented a new method to estimate the planar extensional viscosity from the slit flow pattern. In this study, the method is improved and tested using four polymer solutions. A new photochromic visualization technique is developed and applied to investigate the velocity field to confirm the validity of the improved method.
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Kazunori SORIMACHI, Tomiichi HASEGAWA, Takatsune NARUMI
Article type: Article
Session ID: 1445
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A viscous fingering pattern have been observed when a fluid is injected into a more viscous fluid through a small hole at the center of a parallel plate. Aqueous glycerin solutions are used as Newtonian fluids, and aqueous glycerin solutions adding polyacrylamide (SeparanAP30) 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. It was found that the solution concentration, gap and air pressure influenced a bifurcation pattern. Furthermore, viscosity and air pressure influenced tip speed of bifurcation in Newton fluid.
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Takehiro YAMAMOTO, Yousuke NAKAMURA, Noriyasu MORI
Article type: Article
Session ID: 1446
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Viscous fingering in surfactant solutions in a rectangular Hele-Shaw cell was studied. The test fluids used for more viscous fluid were aqueous solutions of CIAB (Hexadecyltrimethylammonium Bomide) with NaSal as salt. The concentration ratio of CTAB to NaSal was 1:7.7 and two fluids with different CTAB concentration i.e. 0.03 mol/l and 0.04 mol/l were employed. Air, less viscous fluid, was injected into the more viscous fluid at various injection pressures. The finger growth changed at a critical wall shear rate: sudden jumping out of a finger-tip was observed. The order of the shear rate is similar to that at which flow curves bend in measurements with a capirally rheometer. The drastic change in finger growth relates to anomalous rheological property of the surfactant solution.
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Wanheng LI, Motoyuki ITOH, Shinji TAMANO, Kazuhiko YOKOTA, Mitsunori Y ...
Article type: Article
Session ID: 1447
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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This paper deals with a flow of an aqueous surfactant solution due to a rotating disc in a cylindrical casing with aspect ratio H/R=2, where H and R is the height of the cylindrical casing and the radius of the rotating disc, respectively. The aqueous surfactant solution (C_<14>TASal), whose concentration is 0.4, 0.8 and 1.2%, is consisted of n-tetradecyltrimethylammonium bromide (C_<14>TABr) and sodium salicylate (NaSal). The swirling flow was investigated using a flow visualization technique and a two-component laser Doppler velocimetry (LDV) system. It was found that the projection was moving up and down at a constant frequency near the rotating disc, as not seen in polymer solutions.
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Takashi Koshiba, Noriyasu Mori
Article type: Article
Session ID: 1448
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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In order to clarify the elongational property of surfactant solutions, we experimentally examined the spinnability of surfactant fluid by a filament streching method. The spinnability was evaluated by a beakup height of filament in stretching process. The mixtures of CTAB and NaSal in distilled water were used as test fluids. From experimental results, it is confirmed that a breakup hight depends on a salt concentration of surfactant solutions. Furtheremore, these results suggest that the elongational deformation is closely connected to a variation of micellar network structure.
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Satoshi OGATA, Keizo WATANABE, Takeshi FUJITA
Article type: Article
Session ID: 1449
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The effect of surfactant solutions on the flow over a flat plate has been investigated by measuring the velocity profiles in the Reynolds number range of 1.1×10^5 < Re < 4.5×10^5. Surfactant solutions were aqueous solutions of oleyl-bihydroxyethyl methyl ammonium chloride (trade name: Ethoquad O/12) in the concentration range of 50 to 200 ppm, to which sodium salicylate was added as a counterion. It was clarified that the boundary layer thickness of surfactant solutions increases significantly comparing with that of tap water at Re < 3×10^5. Velocity profile of the boundary layer for surfactant solutions gradually increases from the outer edge of the boundary, and approaches the turbulent velocity profile of Newtonian fluid. The shape factor with surfactant solutions has a constant value of 1.7 < H < 2, and transition to turbulent is not appeared clearly.
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Mizue MUNEKATA, Hiromitsu YAMAKAWA, Kazuyoshi MATSUZAKI, Hideki OHBA
Article type: Article
Session ID: 1450
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Surfactant solution for drag-reducing has non-Newtonian property with is shear-thinning viscosity. In this study, secondary flow of the surfactant solution in a 90° square bend is investigated by using PIV. The flow in bulk velocity V_b = 2.0m/s has the drag-reducing rate of 26% in the bend: The radial velocity component, V_y, is integrated over a given volume in order to estimate the magnitude of secondary flow. It is shown that the V_y component of secondary flow in the surfactant solution is greater upstream in the bend than that in water, and smaller downstream. In the whole region of the bend, the magnitude in the surfactant solution is smaller than that in water.
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Koichi NISHIMURA, Masatsugu MATSUMOTO, Yutaka YAZAKI, Mamoru TANAHASHI ...
Article type: Article
Session ID: 1451
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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Temperature dependence of drag reduction with surfactant solution is discussed. To clarify the range of the drag reduction, time scale ration of the additive to coherent fine scale eddy is introduced for the near wall turbulence. Since the time scale of the additive is considered to be constant under the conditions of constant additive concentration and temperature, the time scale of the coherent fine scale eddy can substitute the time scale ratio. The maximum drag reduction ratio has no temperature dependence for 500ppm and higher, while it decreases with the temperature for 100 ppm. For 500 ppm and higher, the upper limit of drag reduction depends on the concentration of the additive when the fluid temperature is 35℃ and above. Temperature dependence of the upper-limit-time-scale increases with the concentration of the additive. The time scale of the additive decrease with both fluid temperature and concentration of the additive.
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Y. Tsubaki, H. Mizunuma, F-Ch. Li, T. Segawa
Article type: Article
Session ID: 1452
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The vortex structures in drag reducing fluids were investigated in transitional and turbulent boundary layer respectively. Using a vibrating ribbon method, two-dimensional disturbance was introduced into the transitional flow, and its growth was observed. The instantaneous velocity distribution was obtained using PIV. The drag reducing additives produced similar change in vortex structure in the transitional flow and the turbulent flow. The polymer additives suppressed the growth of the vortex and its lift up in the transition and the turbulent flow. The surfactant solutions brought out the maximum drag reduction in the turbulent flow, and inhibited vortex structure in the transitional and the turbulent flow. These observations suggest the similarity between the mechanism of turbulence modification in the transitional and the turbulent flow.
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Shigeki IMAO, Yasuaki KOZATO, Kazuhiro MURASE
Article type: Article
Session ID: 1453
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The stability of the flow of drag-reducing solutions such as polymer solutions and surfactant solutions between concentric cylinders with the outer cylinder rotating and the inner one at rest has been investigated by mean of flow visualization. Two kinds of polymer solutions and a surfactant solution are used, all of which show remarkable drag reduction in the turbulent region. Critical Reynolds number at which turbulence appears decreases with an increase in the concentration of additives. Appeared turbulence was not spiral turbulence observed in the case of water but large scale one in the case of polymer solutions and dislocated Taylor vortex like pattern in the case of surfactant solution. It is found that surfactant solution shows remarkable hysteresis at critical value, whereas it is not so remarkable in the case of polymer solutions.
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Teruo KUMAGAI, Yoshifumi IKEDA, Ken MUROI
Article type: Article
Session ID: 1454
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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The dilute addition of natural foods such as fermented soy-beans, grated yams and a kind of seaweeds to water flow within a circular pipe is newly recognized to control turbulent flow and to be effective for the degradation of frictional loss of the pipe flow. It should be noted that these natural foods are harmless to the environment. These additives show the degradation of the frictional loss of pipe flow as same as the usual artificially-synthetic additives, which are generally harmful to the environment. The net-structure of natural foods in pipe flow is iced instantaneously using liquidized nitrogen and is visualized by using optical and electronic microscopes. As the results the degradation effect of frictional loss of pipe flow is newly made clear to be caused by the control of turbulent flow near the pipe wall.
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Akiyoshi KURODA, Jun SUZUKI, Kazuhiko KUDO
Article type: Article
Session ID: 1455
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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A model to simulate the drag reduction by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct numerical simulations are carried out with this new model using the rigid dumbbell element as a discrete element model and it is shown that the drag reduction up to 37% drag reduction rate is reproduced. The mechanism of the drag reduction is discussed based on the DNS database.
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Yusuke TAKAHASHI, Seiichi ANDO, Shuichi IWATA, Hideki MORI, Tsutomu AR ...
Article type: Article
Session ID: 1456
Published: September 04, 2004
Released on J-STAGE: August 01, 2017
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For solving viscoelastic flow problems including singular point, such as die-swell and/or sudden contraction flows, the singular / decoupled finite element methods (SFEM) are investigated. We have calculated the die-swell flows at higher Weissenberg number using SFEM; where all of nodal points for the velocity, pressure and stress fields are removed from the singularity, and the shape of singular elements are sector. When introducing such singular elements to the traditional FEM programs only with ordinary elements, the meshing and topology should be changed completely due to the shape of singular elements. To avoid such difficulty, we propose a singular elements, which are associated with new special interpolation functions; and the shape of singular elements are quadrilateral so as to keep compatibility with traditional FEM programs. It is found that the new SFEM yields the more smooth results.
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