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Koichi ARAGA, Tsuneo AZUMA
Article type: Article
Session ID: K-1214
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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This paper describes the LDV measurement of the generation and growth of the turbulent puff and slug in the transitional pipe flow of a surfactant (TTABr)-distilled water solution, the concentration of which was smaller than 400 ppm. The test pipe was a straight glass tube of 5.02 mm in inside diameter and 2576 mm in length. A large perturbation was introduced by a ring-shaped roughness element installed at a downstream location of 77D from the pipe entrance. In the straight pipe without the roughness element, while laminar flow is kept to 15300 under water flow, a quasi-laminar state at 2400<Re<11000 and the initiation of transition to turbulence at Re=11000 were clearly observed under 400 ppm solution. The result of the experiment with the roughness element showed that, as the concentration of the surfactant increases more than 260 ppm, the critical Reynolds number, in which the turbulent slug and puff begin to appear, increases and the growth rate of turbulent slug decreases.
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Kazunori SORIMACHI, Hiroshi WATANABE, Tomiichi HASEGAWA, Takatsune NAR ...
Article type: Article
Session ID: K-1215
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Frictional torque which is generated in the flow between two disks, one rotating and the other fixed, is measured. Water and aqueous glycerin solutions are used as Newtonian fluids, and aqueous glycerin solutions adding polyacrylamide (Separan) are used as viscoelastic fluids. It was found that the torque is mainly concerned with the viscosity and the disk speed for Newtonian fluids, but for viscoelastic fluids it takes values greater than those estimated with the viscosity possessed by the solutions. Non-dimensionalized torque is correlated with Reynolds number for Newtonian fluids, but larger for viscoelastic fluids than for Newtonian fluids.
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Satoshi OGATA, Keizo WATANABE, Shinobu MATSUDA
Article type: Article
Session ID: K-1216
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The flow around a circular cylinder in surfactant solution was investigated experimentally by measuring the pressure distribution. Test surfactant solutions were Ethoquad O/12 at concentrations of 50, 100 and 200 ppm, and sodium salicylate was added as counterion. It was clarified that the pressure coefficient behind separation point around a circular cylinder in surfactant solution was larger than that in tap water, and the separation angle was increased with increasing the concentration of surfactant solutions. The drag coefficient of a circular cylinder in surfactant solution was smaller than that in tap water in the Reynolds number range of 10000 < Re < 50000, and no drag reduction occurred at Re=6000. The drag reduction ratio was increased with increasing the concentrations of surfactant solutions. The maximum drag reduction ratio was about 35%.
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Masatada SHINDOU, Noriyasu MORI, Tsutomu TAKAHASHI, Kiyoji NAKAMURA
Article type: Article
Session ID: K-1217
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Mechanism of the occurrence of the wavy texture in slit flows of a liquid crystalline polymer (LCP) solution is studied through start-up flows using 50wt% aqueous solution of hydroxypropylcellulose (HPC). The average shear strain at the onset of the wavy texture is examined in the flows through slits with various entrance geometries. The shear strain is independent of an average shear rate except for the low shear rates below 2s^<-1>. Furthermore, the transition of the texture is revealed at the start-up experiment using a piston.
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Takatsune NARUMI, Fumio SATO, Tomiichi HASEGAWA, Howard SEE
Article type: Article
Session ID: K-1218
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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We have examined Bingham like property of concentrated suspensions with non-Brownian spheres in a squeezing film flow. Apparent yield stress has been estimated with a very weak squeezing flow between a spherical surface with a large radius of curvature and a flat plate. The apparent yield stress has gap dependence and is larger than that measured with a torsional shear flow between parallel plates. These trends are more remarkable in monodispersed system in particle size. It is expected from these results that the monodispersed suspension generates a highly aligned structure and the influence of elongational deformation of the structure is significant in the squeezing film for the concentrated suspension.
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Atsuhide KITAGAWA, Masaaki ISHIKAWA, Yuichi MURAI, Fujio YAMAMOTO
Article type: Article
Session ID: K-1219
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The microscopic flow containing bubbles and solid particles shows complicated behavior but it sways performance of material surface characteristics in fluid machineries and environmental devices. This paper shows simulation technique for the dispersed three-phase flow and the application results for induction flow in the vicinity of a wall with arrangement of rectangular obstacles. Parametric study has been done and revealed that the probability of bubble-capturing in a cavity flow between the obstacles was higher than that of particle.
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Shohji TSUSHIMA, Atsushi HASEGAWA, Tetsuya SUEKANE, Shuichiro HIRAI, Y ...
Article type: Article
Session ID: K-1220
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Magnetic Resonance Imaging(MRI) is applied to measure velocity inside clay that intrudes at a sudden contraction step. The experiments were conducted with a specially-designed non-magnetic apparatus on which two type of contraction step can be assembled. It is demonstrated that a tagging pulse method gives satisfactory MR images of clay which leads to measure fluid velocity of clay in a quantitative manner. It is also revealed that slip velocity between clay and wall depends on fluid velocity, that is of importance to conduct numerical simulation in determining boundary condition. Finally, expeirmental data are compared with those obtained by numeical calculation where power-law model were applied to clay as non-Newtonian fluid.
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Fumihiko Mikami, Atsushi Sasada, Nobuhide Nishikawa
Article type: Article
Session ID: K-1221
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Experimental studies have been made on turbulent structures of water and drag-reducing turbulent flow in a straight duct of rectangular cross-section (15mm×30mm). Velocity measurements were made using a high-resolution CCD camera with a telecentric lens for Particle Image Velocimetry. Time averaged statistics of the turbulent flow show a reduction in both the wall-normal velocity fluctuations and the Reynolds stress through out the channel. Maps of fluctuating velocity vectors show dramatic suppression of vortical motions in drag-reducing polymer solution flow, where the formation of groups of the fluctuating velocity vectors orienting to the streamwise direction was observed near the wall.
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Hideo ASAMA, Tomiichi HASEGAWA, Takatune NARUMI, Ryo MUNEMURA
Article type: Article
Session ID: K-1222
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Elasticity of viscoelastic fluids can be estimated from the anisotropy of refractive index by optical stress law. In the present study, we observed the anisotropy of refractive index in the elongational flow field of a two-dimensional channel, using Mach-Zhender interferometer. The displacement of interference fringe of this interferometer indicates variations of refracrtive index. The anisotropy of refractive index was not seen in the flow field of water. However, it was observed in the flow field of cetyltrimethylammonium bromide (CTAB) in aqueous sodium salicylate (NaSal). CTAB-NaSal solution is known to have strong elasticity, and therefore it is thought Mach-Zhender interferometer is promising to estimate the elasticity of fluids.
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Tomiichi HASEGAWA, Ryo MUNEMURA, Takatsune NARUMI, Hideo ASAMA
Article type: Article
Session ID: K-1223
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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This paper presents the rheo-optical experimental result of flow through a small orifice. PEO 3000ppm and CTAB-NaSal water solutions are used as test fluids. Two laser beams having orthogonal planes with each other are exposed to the jet issuing out of the small orifice. Change of interference fringe means an anisotropy of the test fluid. CTAB-NaSal shows the anisotropy, which is thought to depend on the property of the test fluid. But the anisotropy is not detected clearly for PEO3000ppm water solution.
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Hayato MORI, Kuniaki TOYODA
Article type: Article
Session ID: K-1301
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Three-dimensional vortical structure and mixing characteristics of an axisymmetric water jet were investigated by a flow visualization technique. The jet was excited by axial and azimuthal perturbations to stabilize and enhance axisymmetric and streamwise vortices. A laser florescent dye and a laser light sheet were used to visualize the jet. The three-dimensional views of vortical structures were constructed by applying the Taylor hypothesis to the jet cross-sectional images. The views reveal the details of the complicated structure. From the three-dimensional view, the unmixing area of jet cross-sectional image was estimated to discuss jet mixing. The result suggests that the simultaneous enhancement of axisymmetric and streamwise vortices is very effective to increase mixing.
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Katsumi MIYAKOSHI, Hiroyuki HANIU
Article type: Article
Session ID: K-1302
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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It is possible to control the spread of a plane jet passively by the vortices from a two-dimensional cylinder installed in the nozzle contraction. In this study, the wake characteristics of a cylinder and the coherent structure of a jet by this passive control method were examined. In wide range of strouhal number Sto based on vortex shedding frequency (fv) and jet exit velocity, the spreads of the jet were found to be suppressed. On the other hand, hi particular cases of Sto being 0.08-0.10, the spread of the jet was remarkably enhanced associated with distinctive peaks of spectrum which arose from the deformation of the vortices by flow contraction in nozzle.
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Fujio AKAGI, Sumio YAMAGUCHI, Youichi ANDO
Article type: Article
Session ID: K-1303
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The effect of constriction ratio β at a stenosed on vortex ring behavior, which was induced by a sinusoidal pulsatile jet flow downstream of stenosed was studied experimentally by means of PTV methods. Phase mean velocity vectors in the downstream region of stenosed model were measured under the condition of β=0.33 and 0.50. It was observed that, in both β conditions, vortex ring was produced during the period of increase in flow rate and was propagated downstream with constant velocity. In the case of β=0.50, the second vortex ring was produced in contiguity with the leading vortex ring, but in the case of β=0.33, it was observed only higher St number, in the case of β=0.33 the vortex ring breakdown was followed during a period. In the case of β=0.50, however, the vortex ring kept propagating with during a few periods.
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Masafumi MIYATA, Ryushi Yagi
Article type: Article
Session ID: K-1304
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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LDV measurements were conducted in the turbulent round jet issuing into a counterflowing uniform stream for velocity-ratios from 0.8 to 7. Similarity of flow fields for the velocity-ratio 5 was confirmed for the jets with diameters of 10mm and 30mm. Also, confirmed was the linear dependence of the penetrating length of the jet into the counterflowing stream over various conditions investigated. Flow pattern is affected by the nozzle shape for velocity-ratios smaller than 1.3. The non-dimensionalized dividing streamline tend to be more slender and pointed with increasing velocity-ratio.
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Hiroyuki TSUNODA, Masamichi SARUTA
Article type: Article
Session ID: K-1305
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The diffusion field of a passive scalar in a circular jet opposing a uniform water flow is investigated using PIV and PLIF techniques. Experiments were carried out for three cases of jet to counter-flow velocity ratios; 2.6, 3.7,4.8. Due to the radial oscillation of the jet penetrating into the counter-flow, the rms concentration fluctuation is found to have a local maximum within the stagnating region. Another distinct indication of the jet meandering is the rms to mean concentration ratio, which shows a rapid enhancement near the stagnation point after maintaining a constant value of about 0.3.
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Atsushi MIURA, Nobuo OGAWA
Article type: Article
Session ID: K-1306
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The flow fields of the jets into uniform counterflowing flow include regions of large diffusion. Investigation of that flow fields is important to estimate the characteristics of the diffusion in general. And the results are useful to discuss the fields of combustion, mixing, etc. Recently we found the negative static pressure zone and no recirculation region, and the results differ from the previous models of the flow fields. The large diffusion of the flow fields is caused by a relative diffusion due to the stretching and the deforming of the vortex tubes. In this paper, the large diffusion of the jets into the counterflowing flow is investigated by the measurements of the velocity and pressure fields and by the visualization of the flow fields.
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Fumihito MURATA, Mikikane HIROHATA, Nobuyuki TANIGUCHI
Article type: Article
Session ID: K-1307
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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It is difficult to express a fully turbulent developing process involving generations, interactions and disintegrations of vortex loops. Because it is actually impossible to express the inlet condition of simulation as well as experiment. Particularly, initial region of jet is open to that's effect. If to make target near region such as material processing, therefore, disagreement between experiment and calculation is fatal problem. In this paper, it is purpose to investigate set-up method of inlet turbulence condition making generations, interactions and disintegrations of vortex loops and to apply this method to hydrogen diffusion jet flame.
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Masaaki NARUSE, Tomomi UCHIYAMA
Article type: Article
Session ID: K-1308
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A slit nozzle jet is analyzed by a three-dimensional vortex method. The vorticity field is discretized into vortex elements and a core spreading method is employed to simulate the viscosity. The mean velocity and turbulent intensity are compared with the measurements so as to discuss the method's applicability.
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Yuji SUZUKI, Nobuhide KASAGI
Article type: Article
Session ID: K-1309
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A novel jet nozzle equipped with a row of miniature electromagnetic flap actuators was developed for active control of mixing and combustion. The spatio-temporal flow structures of the axsymmetric and coaxial jets were studied through flow visualization and quantitative measurements by PTV, PLIF and LDV. It is demonstrated that various disturbances introduced in the initial shear layer by the flap actuators can significantly modify the process of formation and evolution of large-scale vortical structures. In particular, when each half cluster of the flap actuators are driven 180 degree out of phase, the jet bifurcates clearly into two branches. For coaxial jet, mixing between the inner and outer fluids was markedly enhanced by the axisymmetric motion. A preliminary attempt for active combustion control shows that the present control scheme is also effective in stabilizing lifted flame.
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Hirokazu SUZUKI, Masaharu MATSUBARA, Takashi YOSHIDA, Toshihiko IKEDA, ...
Article type: Article
Session ID: K-1310
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The two dimensional turbulent jet impinging to a circular cylinder has been investigated. The distinct decrease of the stagnation pressure against the total pressure in free jet was observed with generation of tone between the exit of jet and the cylinder in range of 3≦x_c/h≦10 where x_c is the streamwise position of the cylinder and h is height of the jet exit. To reveal the mechanism of this self-excited oscillation, the velocity profiles and the spectrum of the velocity fluctuation upstream the circular cylinder has been measured using hotwire anemometry. The velocity spectrum shows that the flow has the periodical flow structures whose frequency coincides with that of the tone, and that the flow structures impinging to the cylinder might makes pressure fluctuation at the cylinder surface.
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Suguru Hirabayashi, Masaharu Mutsubara, Takashi Yoshida, Yoshiaki Tsuc ...
Article type: Article
Session ID: K-1311
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Pressure measurements and flow visualizations of the rectangular jet colliding with a circular cylinder has been made to investigate separation with different diameters of the circular cylinder. The visualizations and the pressure distributions are well correlated and shapes of separation regions strongly depend on the diameter of the circular cylinder.
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Toshihiko SHAKOUCHI, Takumi MARUYAMA
Article type: Article
Session ID: K-1312
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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It is well known that a round jet has a large vortex structure, but the flow chracteristics, vortex structure, of resonance jet has not been made clear yet. In this study, the flow characteristics, vortex structure, of resonance free and impinging jets are examined experimentally using flow visualization technique, and it is made clear that the resonance free and impinging jets have large vortex structures and their behavior can be controlled by chainging the volume of resonance room. The vortex structure of resonance free jet is very effective to enhance mixing or diffusion. The resonance impinging jet flows on the plate extending vortex rings with a certain interval.
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Akinori MURAMATSU, Yoshinobu ERA
Article type: Article
Session ID: K-1313
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A disturbance produces by a jet impinging on an object. The turbulence is useful for the mixing. The mean and r.m.s. values of concentration and velocity were measured in the wall jet regions of impinging jets by the hot-wire techniques. The wall jets were formed by impinging respectively helium; air and carbon dioxide gas jets to the disk or cone with various vertical angles set up in still air. The mixing of gases is very enhanced by impinging jets in comparison with an ordinary free jet. The relation of the measured values and the vertical angle is discussed. The relationship between decays of maximum values of concentration and velocity along the main stream and the vertical angle is expressed.
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Shinya KATO, Kunikazu KONDO, Yoshihiro INOUE, Shintaro YAMASHITA
Article type: Article
Session ID: K-1314
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Coherent structures in the near field of a free jet have been studied. Experiments are carried out for the free jets issuing from round and square nozzles using a water channel. Instantaneous velocity profiles are obtained in the radial direction by using an ultrasonic velocity profile (UVP) monitor. Coherent structures in the radial direction are investigated in terms of the proper orthogonal decomposition (POD). In the distributions of eigenfunction at each POD mode and energy contribution from each POD mode, there is no remarkable difference between round and square jets. In the power spectra of the random coefficient at the first POD mode, however, there is a broad peak in the case of round jet.
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Masashi MATSUMOTO, Naoshi KURATANI, Yuji IKEDA, Tohru MITANI
Article type: Article
Session ID: K-1315
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The pressure distribution around the fuel injection nozzle, within a scrara-jet combustion chamber are visualized using pressure-sensitive paint (PSP). The freestream Mach number is 2.4 and injection Mach number is 1.0. The flow fields with jet-to-crossflow dynamic pressure ratios of from 0 to 1.2 were examined. The visualized flow field showed high pressure regions of the bow shock waves and secondary flow.
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Kazuhisa MATSUYAMA, Nobuo OGAWA
Article type: Article
Session ID: K-1316
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The sandblasting is known for a surface processing techniques in industrial world. Recently, the technique applies to micro processing for electric circuit. But the characteristics of the technique using the gas-solid impinging jet depend on the length between the sandblasting nozzle and the works. Especially the technique has characteristics to process, which the surface of the works shows uneven distribution for the short length between the sandblasting nozzle and the works. The characteristics are affected by the characteristics of the flow fields of the impinging jet, and the change of that affects on the trajectories of the solid particles in the gas-solid. In this paper, experiments and numerical simulations clear the flow fields of the gas-solid impinging jets, and performance of the sandblasting nozzle is estimated. Cylinder Bundle, Numerical Calculation
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Satoshi KANAWA, Munetaka ARAI, Takeharu KOUBAYASHI, Risaburo OBA
Article type: Article
Session ID: K-1317
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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In our SIT, a highspeed water jet tunnel of vertical circulating type was newly established for jet peening tests, whose cavitation nuclei are suitable for both cavitation and shock waves. The nuclei and the cavitation aspects are systematically evaluated. We also quantitatively predict the waiting time necessary for nuclei stabilization and for cavitation stabilization. Through huge shock rings, we can clearly observe several projected jets, water column separation and so on.
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Shigetaka FUJITA, Takashi HARIMA, Hideo OSAKA
Article type: Article
Session ID: K-1318
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The mean flowfield of a three-dimensional turbulent jet issuing from a rectangular nozzle (AR=12.5) with a rectangular notch (AR=2.5 and 7.5) at the midspan was measured experimentally. The experiments were made using an X-type hot wire probe and the linearized constant temperature anemometers to measure streamwise mean velocity, and a 5 holes pitot-static tube to measure spanwise and lateral mean velocities. Reynolds number was kept constant at 30000. The aim of this study is to examine a control for the flowfield of the rectangular jet using a rectangular notch with different aspect ratio. From the results, it is clarified that the development of the present mean flowfield is controlled by the magnitude of aspect ratio of the rectangular notch.
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Nobumasa SEKISHITA, Hideharu MAKITA, Yutaka WATANABE, Atsushi WATANABE
Article type: Article
Session ID: K-1319
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Effects of bimodal acoustic excitation on the behavior of coherent vortices were investigated in a two-dimensional parabolic jet exhausted from a nozzle of 10mm(=2h)×400mm through hot-wire measurement and multi-smokewire visualizations. The subharmonic velocity component increased remarkably in the streamwise direction when the phase difference was given as zero between the fundamental component, u_f, and its subharmonic component, u_s, measured at X/2h=3, Y/2h=0 where the velocity components could be detected most noticeably. In this case, vortex pairing occurred quite periodically at about X/2h≒7, 6.5 and 6 for u_s/u_f=1, 2 and 3, respectively and the vortex arrangement changed into antisymmetric one after the pairing. When the phase difference was given as 120°, the vortex pairing became to occur more occasionally with decreasing u_s/u_f. When the two vortices didn't paired, the symmetric arrangement was kept until far downstream.
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Takahiro KIWATA, Atsushi OKAJIMA, Shigeo KIMURA, Tatsushi KOBAYASHI
Article type: Article
Session ID: K-1320
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Coaxial jets have been experimentally studied, and both the outer annular jet and the inner circular jet are excited by the sound wave from speakers with controlled initial phase differences. We have measured velocity and turbulent intensity distributions of the excited coaxial jets with the velocity ratio of 0.6 and the forcing frequency of 333Hz, which is a half of natural vortex frequency. It is found that the intensity of fluctuating velocity in the outer mixing region for the excited outer jet increases than the excited inner jet, and the excitation of the outer jet is indeed more effective than the other excitation in the jet mixing enhancement. For the excited both jets, the excitation of the phase difference φ=0° produces large-scale structures in the shear-layers, and the intensity of fluctuating velocity in the both mixing regions increases. It is shown that the excitation of the phase difference φ=260° can reduce the turbulence intensities in the mixing regions than the excitation of the other phase difference.
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Toru KOSO, Shinya KAWAGUCHI, Hiroshi HAYAMI
Article type: Article
Session ID: K-1321
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Flow and pressure in a fluidic oscillator attached to a plane turbulent jet are studied experimentally by using hot-wire anemometers and semiconductor pressure transducers. Ensemble averaged velocities and pressures are deduced to examine the dynamics of the oscillating flow field. The measured port pressure difference can simulate the flow in the connecting duct and explains the jet deflection well. The variation of port pressure with duct flow rate is examined by air injection test and it is concluded that the port pressures are controlled by the balance of jet entrainment and air supply in the control ports. The switching process is explained well in terms of this mechanism.
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Tsutomu NOZAKI, Masashi YONETA, Hachiro DOI, Minoru FUKUHARA, Masahiro ...
Article type: Article
Session ID: K-1322
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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It has been found that a compound swirl flow which is composed of a round jet and a coaxial annular swirl jet is very useful for a push-pull type ventilator. As a fundamental study on the compound swirl flow, the mean velocity components were measured using an inclined hot wire probe. In the case of the swirl number 0.38 and the flow ratio of annular swirl jet to the round jet 0.18, it was found that by combining the round jet and a coaxial annular jet the jet radius reduces and the swirl flow collapses in the down stream direction. Then there exists the flow where the energy density is relatively strong in the near region of the jet.
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Masahiro NAKASHIMA, Takahide TABATA, Akira SHIGEYOSHI, Hui Li, Tsutomu ...
Article type: Article
Session ID: K-1323
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The jet issuing along the cylinder wall in its longitudinal direction has been dealt with in this paper. The attention has been focused on the flow aspect in the cross section normal to the flow. The effects of the curvature of the cylinder on the flow aspect have been investigated by means of the flow visualization and the image processing, using some cylinders with various diameters. As a result, it has been found that the large-scale swirling flow has been recognized in both sides of the jet and the jet mid-plane fluctuates largely due to this swirling flow. It has been also clarified that the jet mid-plane swings largely for the cylinder with a certain curvature.
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Yasuaki KOZATO, Shigeki IMAO, Toshio TANAKA
Article type: Article
Session ID: K-1324
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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This study is concerned with the temporal and spatial structure of a radial jet which reattaches on a side wall. Large-scale unsteadiness of the flow was clarified experimentally by velocity measurements with the conditional sampling technique. The flow oscillates up and down periodically in the arbitrary section. And this oscillation shows a different behavior if the circumferential position changes in the same time. Also, the oscillating frequency decreases as the offset distance between the nozzle and the side wall increases.
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Shinzaburo UMEDA, Kiyoshi HORII, Shinzo MANMOTO, Wen-Jei Yang, Akira T ...
Article type: Article
Session ID: K-1325
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A concurrent-flow thin-liquid layer is placed over the intersecting-flow jet to compose a hybrid assembly in the present work. Flow visualization study is performed to disclose flow pattern using high-porous, polymer particles and to observe streamlines at the jet interface by means of fluorescent dye illuminated with a laser light sheet. A laser Doppler velocimetry(LDV) is employed to determine the timewise variation of velocity distribution and its variation, turbulence strength, and Reynolds stress near the jet interface. Characteristics of the interaction of thin-liquid sheet with concurrent intersecting-flow are disclosed.
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Shinsuke Mochizuki, Katsuhiko Tone, Hideo Osaka
Article type: Article
Session ID: K-1326
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Effectiveness of an active management technique of a stronger wall jet was studied experimentally with a streamwise vortex generated by a half-delta wing located on the wall. The angle of attack is oscillated at a constant frequency to amplify spanwise wandering of generated streamwise vortex. The mean velocity and Reynolds shear stress profiles were measured and momentum flux was calculated. The interaction between the stronger wall jet and streamwise vortex reduces magnitude of Reynolds shear stress in the outer layer. However, momentum flux is increased. Remarkable decrease of static pressure due to the streamwise vortex was confirmed throughout the whole shear layer. The active management technique controls these effects of vortex in the interaction process.
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Yu FUKUNISHI, Yuzuru YOKOKAWA, Seiichiro IZAWA
Article type: Article
Session ID: K-1327
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Control of the velocity fluctuation in the turbulent separation flow over a cavity with a resonator is attempted. The objective of this research is to reduce the aerodynamic noise generated by the separating flow. Active flow control technique using the piezoceramic device that expands or shrinks parallel to the freestream is carried out. Experimental results show that though it is difficult to change a structure of the velocity fluctuation field, by adding devices such as partition plates inside the cavity and resonators, a wavy pattern that is 180 degree out of phase along the spanwise direction can be created. Reduction in the aerodynamic noise due to the control is also observed.
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Toshihiko Shakouchi, Toshitake Ando, Keigo Miyata, Masahide Kinoshita
Article type: Article
Session ID: K-1328
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The time averaged, steady, flow in a sudden contraction flow passage has two distinguished clockwise vortices which appear just before and after the contraction. The latter vortex makes decrease the effective cross sectional area passing through the flow and increase the flow resistance. But, in practice, vortex is shed one by one periodically from the edge of the contraction. In this study, the mean and vortex shedding flow characteristics are examined and a simple method to control and suppress the arising vortex just after the contraction is shown.
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Hitoshi ISHIKAWA, Osamu MOCHIZUKI, Masaru KIYA
Article type: Article
Session ID: K-1329
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The process of the separation was investigated experimentally in the single-side expansion type diffuser. The inclined wall of the diffuser was opened with time at constant angular velocity. The flow visualization by tufts on the inclined wall shows that the separation bubble grows before separation. The surface pressure fluctuation on the inclined wall was amplified before separation. FFT analysis of the pressure fluctation shows the particular spectrum peak about 500 Hz, This "precusor signal of separation" was found to be related the instability due to an inflection point of the velocity profile. Then, transition into the turbulent flow occur in the diffuser.
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Manabu SAITO, Tadashi MORIOKA, Shinji HONAMI
Article type: Article
Session ID: K-1330
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The purpose of this study is to develop the closed loop control system of the reattachment process in a backward facing step flow by a row of the vortex generator jets. A row of injection holes which covers full span is located upstream of the step. As a control parameter of the jets, the effects of the injection hole pitch and the jet velocity ratio on the reattachment process are investigated. A micro wall flow sensor was used for measurement of forward flow fraction. It is found that the reattachment line is almost parallel to the spanwise direction in the pitch from l0d to 20d, and that the reattachment length is decreased with an increase of the velocity ratio.
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Yasuhiro KOMATSUZAKI, Hiroaki HASEGAWA, Kazuo MATSUUCHI, Katsuyuki OHO ...
Article type: Article
Session ID: K-1331
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The vortex generator jets (VGJs) method can control flowfields or especially suppress flow separations in a wide range of conditions. The experiments were conducted using a low speed wind tunnel with a two-dimensional diffuser. To make better separation control we investigated the effect of jet orifice shape. Orifices of square shape were investigated instead of circular ones. Vorticity distributions and the static pressure in the divergent portion of the wind tunnel were measured. Pressure recovery was improved a little for square orifices at a certain pitch angle. At the angle, 45deg., for square orifices, we can keep the negative vortices near wall. However we found that the effect depends heavily on the pitch angle of jets than on the orifice shape.
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Y. XIE, M. NISHI, K. YOSHIDA
Article type: Article
Session ID: K-1332
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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In order to develop the vortex generator jets method for flow control, the far-field and near-field of the counter-rotating vortex pairs produced by a pair of inclined round jets embedded in turbulent boundary layer are studied numerically. In the calculation, the incompressible RANS (Reynolds Averaged Navier-Stokes) equations with the standard and RNG k-ε turbulence model were solved using the commercial code STAR-CD which employed the unstructured mesh. The typical results are compared with the experimental data. The effects of jet parameters such as velocity ratio on the strength of the vortices generated by the jets are investigated. The results do clarify some physical mechanisms of the flow field generated by a pair of pitched and skewed jets.
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Yoichi KAMIKUCHI, Hiroshi MAEKAWA
Article type: Article
Session ID: K-1333
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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An actuator to control hairpin vortex was made and tested in a water channel, which generates a circulation opposite to those by the hairpin vortices. Velocity fluctuation measurements by hot-film in the boundary layer show the decreasing of u-disturbance. Actuation may control the hairpin vortices -reduction of the magnitude of vorticity. The decreasing of the vortices of ω_x is due to opposite tilting (ω_2∂u/∂z<0), ω_y and ω_z are weakened by vortex compressing (ω_y∂v/∂y<0,ω_2∂w/∂z<0).
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Shuji TANAKA
Article type: Article
Session ID: K-1334
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Some aspects of coherent structures in turbulent wakes of obstacles with flow separation have been given and recent findings have been reviewd. The features of the large-scale organized structures have been presented and the procedures for their eduction, such as data acquisition and data processing, have been shown. Some studies on the control of large-scale organized structures behind two-dimensional cylinders as well as complicated natures of three-dimensional organized vortex structures behind a finite circular cylinder have been given.
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Masatoshi SANO, Kenichiro SAKURABA, Syoji KAMIUNTEN
Article type: Article
Session ID: K-1335
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Experiments have been performed for a turbulent channel flow over a backward-facing step. The backward-facing step flow is controlled by equipping the slit in upstream of the step. Angle of the slit is changed 30° and 45°. The velocity profiles, turbulence intensities and wall shear stress are measured using the split hot film probe and the micro flow sensor. It is found that enhancement of the heat transfer is related to the increase of streamwise velocity and turbulence intensity in the near-wall region.
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Takashi OGAWA, Masato TAKAI, Shinji HONAMI
Article type: Article
Session ID: K-1336
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A study on flow around the micro device is strongly required in MEMS development. The objective of this paper is to study dependence of Reynolds number on reattachment process over a backward-facing step in low Reynolds number flow. The Reynolds number based on step height H is 190-5730 and reattachment length was measured by Micro Flow Sensor (MFS) in a Micro Sensing Wind Tunnel which was constructed in the present research program. The reattachment length from 8H to 21H is observed depending on Reynolds number.
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Masanori MATSUMURA, Katsumi MIYAKOSHI, Hidenori MORIUCHI
Article type: Article
Session ID: K-1337
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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A periodicity of vortex shedding in the wake of a two-dimensional bluff body is reduced by a splitter plate. The purpose of this investigation is to understand the effect exerted on the vortex shedding properties by position and width of a slit on the splitter plate. As the result, it was found that there are specific conditions of slit position and width which intensify more periodic vortex shedding than wake without splitter plate.
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Toshiharu MURAMATSU, Kozo SUDO, Hideki HIBARA
Article type: Article
Session ID: K-1338
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Fluid-structure thermal interaction phenomena characterized by stationary random temperature fluctuations, namely thermal striping are observed in the downstream region such as a T-junction piping system of liquid metal fast reactors (LMFRs). Therefore the piping wall located in the downstream region must be protected against the stationary random thermal process which might induced high-cycle fatigue. This paper describes thermohydraulic characteristics of velocity and temperature fluctuations at the downstream region based on numerical results with a computer code system which consists of three thermohydraulics computer programs AQUA, DINUS-3 and THEMIS and of three thermomechanical computer programs BEMSET, FINAS and CANIS, for an actual thermal fatigue event occurred at a French LMFR Phenix.
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Kozo SUDO, Hideki HIBARA, Toshiharu MURAMATSU
Article type: Article
Session ID: K-1339
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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The flow at a T-junction piping system was investigated experimentally. The flow field was visualized by injecting the dye. As a result, it was clarified that the flow at the T-junction piping system was approximately classified into three flow patterns by the ratio of velocity of the main pipe flow to velocity of the branch pipe flow, β, and that vortex street was formed by branch pipe flow under the condition of β≒0.5〜1.5 and the frequency of vortex shedding reduced with increasing β.
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Satoshi MURAKAMI, Toshiharu MURAMATSU, Kozo SUDO, Hideki HIBARA
Article type: Article
Session ID: K-1340
Published: August 22, 2001
Released on J-STAGE: August 01, 2017
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Numerical analyses for a turbulence mixing water experiment, were carried out using a direct numerical simulation code DINUS-3. From the calculated results, it was confirmed that the numerical method is applicable to the evaluation of three flow patterns, i.e., an adhesion flow, a deflection flow and an impinging flow, which were measured in the experiment. Also, arched vortex characteristics agreed well with the experimental results in the adhesion flow condition.
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