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Naoya TANIGUCHI, Akihiko KAKEGAWA, Takeharu KOBAYASHI, Satoshi KANAWA, ...
Article type: Article
Pages
97-98
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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A typical viscous transient flow around an impinging water jet is carefully observed, when the jet just starts to flow and begins to impinge upon a horizontal wall vertically, by means of a particle-image-velocimetry so-called PIV. The jet is upwardly ejected from a 1.64mm-dia nozzle towards the horizontal wall. The transient flow aspects are highspeed-photographically observed by means of the double-pulse YAG-laser of 200ns in exposure time. Clearly, the transient flow aspects are quite different from the steady counterpart.
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Junichi OHTA, Ohki SUHARA, Yuichi MURAI, Manabu IGUCHI, Yoshiteru MIZU ...
Article type: Article
Pages
99-100
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This paper describes the turbulent flow characteristics of axisymmetric non-pulsating and pulsating jets measured by PIV (Particle Imaging Velocimetry). The PIV measurement is made for a pulsating jet at an amplitude ratio of 0.25,a Strouhal number St of 0.17,and a Reynolds number of 1070. According to the measured velocities, the fluid motions are classified into four quadrant categories, i.e. ejection, outward interaction, sweep, and inward interaction. The contributions of these classes of motion to frequency are analyzed. The present result at St=0.17 and a dimensionless distance of z^^-=4 is different from the previous one measured at St=7.8×(10)^<-4> and z^^-=20. It is clear that the frequency of ejection is dominant and the frequencies of the inward interaction and the sweep become approximately equal for phases just after passing the maximum velocity.
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Hayato MORI, Kuniaki TOYODA
Article type: Article
Pages
101-102
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The three-dimensional vortical structure of a circular water jet was 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 view of vortical structure was constructed by applying the Taylor hypothesis to the jet cross-sectional images. The view reveals the details of the complicated structure. From the three-dimensional view, the area of jet boundary surface was estimated to discuss jet mixing. The result suggests that the enhancement of axisymmetric and streamwise vortices is very effective to increase mixing.
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Atsunori KIMURA, Junjiro IWAMOTO
Article type: Article
Pages
103-104
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Pulsating jet generated by discharge of pulsating flow through a pipe has strong unsteadiness, which makes it difficult to measure the flow pattern experimentally. Every effort has been made so far to obtain the flow properties in the pulsating jet by numerical method, while the experimental technique has also been sought. In the present study a static pressure probe for fluctuating supersonic jet is designed and used to examine static pressure history of the pulsating jet. In addition, instantaneous static pressure distribution along the jet axis is obtained by combining this result with visualization study. In this paper the procedure of the experimental method and the result of measurement are described.
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S. Shimizu, J. Anami, M. Sakurai
Article type: Article
Pages
105-106
Published: July 31, 2000
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Experimental studies are carried out to clarify the structures and erosive properties of cavitating jets issuing from rectangular nozzles. The jet is supplied from a high-pressure pump and injected through a rectangular nozzle of aspect ratio of two or four. It discharged into a test cell at specified constant pressure and impinges against a test specimens of aluminum alloy. The structures of the jets are observed by instantaneous photographs and high-speed photography. The experiments are conducted at the injection pressure of 18 MPa. It is shown that the structures and erosive properties of the rectangular jets are completely different from those of circular cavitating jets.
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Akihiko KAKEGAWA, Yukio ITO, Hajime YAMAGUCHI, Risaburo OBA
Article type: Article
Pages
107-108
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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It is known that high speed and intermittent protrusion occurs on the surface of a cavitating submerged water jet. In the present report, particularly, protrusion which arises between the exit of a nozzle and the 1^<st> peak area is focused and photographed by a high-speed-video-camera in order to measure the protrusion velocity. Consequently, it is found that such high speed protrusion is in a supersonic state because the sound velocity is extremely declined under the influence of the void fraction around a submerged water jet. It also emerges that the interfacial behavior of such protrusion differs remarkably with the forms of the nozzle and the values of the injection pressure.
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Masaki ENDO, Junjiro IWAMOTO
Article type: Article
Pages
109-110
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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When a shock wave is discharged into the atmosphere from an open end of a pipe, a vortex ring is formed at the rim of the pipe end and goes downstream. In the process of vortex development a shock wave forms in the vortex ring. Small vortices generated at a jet boundary are sucked into the vortex ring and interact with the shock wave so that pressure waves, which are one of sources of noise, are scatterd. The formation of the shock wave does not only depend on Mach number of the discharged shock but also the strength of compression wave following the discharged shock. In order to analyze such a flow field the experimental study, i.e., optical visualization of the flow field is made at different Mach numbers or different strengths of compression wave. In this study the relation of the behavior of the downstream flow field with a profile of the pressure waves propagating in the pipe is discussed.
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Yoko SAKAKIBARA, Masaki ENDO, Junjiro IWAMOTO
Article type: Article
Pages
111-112
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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When an axisymmetric underexpanded jet impinges on a flat plate perpendicularly, the feedback loop of the sound waves in and around the jet is known to cause the oscillation of the whole flow field. In this paper, the radial underexpanded jet issuing from a nozzle which consists of a tube and a cylinder, face to face each other, is studied experimentally and numerically. Such flow field can be considered as a simple model of the wall jet on the plate of impingement. In the experimental photographs, it is found that some shock rings appear around the nozzle and that the distortion and the deformation of the rings occur. They are considered to be caused by the motion of the vortices around the jet. Such oscillatory phenomena are shown by the computational results. Furthermore, the feedback mechanism of the radial jet is also discussed in connection with the oscillation of axisymmetric impinging jet.
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Fujio AKAGI, Sumio YAMAGUCHI, Youichi ANDO, Kimitaka MINAMI
Article type: Article
Pages
113-114
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The effect of pulsatile flow conditions on vortex behavior downstream of stenosed was studied by means of PTV methods. Phase mean velocity vectors were measured, in the region downstream of stenosed model with 89% area reduction, under the condition of sinusoidal pulsatile flow of mean Reynolds number Re=100∿300 and Stokes number St=151∿410. In each condition, vortex ring were induced by jet flow behind the stenosed, during the period of increase in flow rate. Vortex rings were propagated downstream with constant velocity, and breakdown were followed. The breakdown position of vortex ring were changed depend on St number but independent of Re number. The ratio of propagation velocity of vortex ring and mean velocity in a period at the stenosed was changed also depend on St number but independent of Re number.
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Toru KOSO, Shinya KAWAGUCHI, Masahiro HOJO, Hiroshi HAYAMI
Article type: Article
Pages
115-116
Published: July 31, 2000
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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 by the balance of lateral momentum. The mechanism to govern the port pressure change is proposed to complete the oscillation model of the flip-flop jet nozzle.
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Yoshinobu ERA, Akinori MURAMATSU
Article type: Article
Pages
117-118
Published: July 31, 2000
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A method of concentration and velocity measurements in the mixing flow fields of two different gases is already developed. This method applied hot-wire techniques can be given the fluctuations as well as the mean values. The actual measurements have been carried out in the various different types of turbulent mixing regions produced by axisymmetric jets. Helium and carbon dioxide gases are individually issued into still air. The types of jets treated here are impinging, coaxial, pulsating, and free jets. In any case, the mean and fluctuating values of concentration and velocity are compared to the those of the free jet. The concentration and velocity distributions are functions of the issuing and surrounding gas densities, and also change by the types of jets.
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Takamitsu OHSHIMA
Article type: Article
Pages
119-120
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This paper describes characteristic features of flow patterns that were experimentally analyzed in the transision region of the two dimensional parallel jet with parabolic velocity distribution. The asymmetrical vortex street or symmetrical vortex street was observed in the jet of water shot out from the slot into two dimensional flow field. There were the asymmetrical voltex street at low Reynolds number, and symmetrical voltex street at hight Reynolds number determind by the width 2b of slot and the jet velocity U at slot. These results fitted the linear approximation mathmatical model by Euler's kinetic equation and continuity equation.
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Tomomi HIROSE, Kotaro SATO, Okitsugu FURUYA, Kinya ISHIZAKA
Article type: Article
Pages
121-122
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In this study the behavior of droplet formation was observed with high-speed video camera for the purpose of determining the accuracy of flow rate measurement by use of droplet method commonly used in the medical practice. It is discussed that the surface tension, viscosity and outlet inclination angle have various effects on the droplet size and no single theory does correlate with the present measurement.
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Yoichi ONO, Kotaro SATO, Okitsugu FURUYA, Kinya ISHIZAKA
Article type: Article
Pages
123-124
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In the control of very small flow rate with use of droplet counting method, the exact determination of droplet volume is critically important. The size of droplet formed is not constant but depends on the properties of liquid, its velocity and many other factors. In this study the characteristics of the droplet formation is examined experimentally and compared with existing theories.
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Tomoya NAKAJIMA, Akiyoshi KUGOU, Takahisa SUZUKI, Teruhiko KIDA
Article type: Article
Pages
125-126
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The floating system has some merits that it can support a material without contact and can do surface treatment with hot jet, so it is used as a supporting system for thin film and thin metal production lines. However, in this system a trouble to give scratch defect and irregular tension creases to material are often seen. The fluid power and cost increase, with the increase of the gap height. To decrease running cost of floating system it is important to clear the characteristic of flow for various nozzle angles of floater and geometrical reciprocal action with floater and plate in detail. The present paper reports the detail pressure distribution on the flat plate by the floater with various nozzle angle, aspect ratio, and that on the plate which inclines to the floater.
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Hiroshi MORIMOTO, Tomoyuki OHYAMA, Masahiro OKUMOTO, Toshihiko SHAKOUC ...
Article type: Article
Pages
127-128
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Ultra fine powder was dispersed by dry dispersing operations which were Jet type, Swirling jet type and Free Suction type, and dispersed particles were collected with a prototype sampling device and clarified a state of dispersion with quantitative analysis. The dispersion efficiency and the evaluation method were studied for various supplying air pressures. It was made clear that the jet type and swirling jet type had higher dispersion efficiency than free suction type for ultra fine powders, and the prototype sampling device and the evaluation method of dispersion were effective for quantitative analysis of ultra fine powders dispersion.
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Junsuke TANAKA, Hiroaki HASEGAWA, Kazuo MATSUUCHI, Yasuhiro KOMATSUZAK ...
Article type: Article
Pages
129-130
Published: July 31, 2000
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 obtain a better understanding of the control we investigated the flowfield near the wall where the separation might occur. We measured the secondary flow and vorticity distribution at the downstream of the diffuser. We find that secondary flow toward the lower wall is not necessary for suppressing separation at target position if there exists a secondary flow of enough strength at the upstream of the position.
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Y. XIE, M. NISHI, K. YOSHIDA
Article type: Article
Pages
131-132
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In order to clarify some physical mechanisms of the development of a longitudinal vortex generated by a pitched and skewed jet, the nearfield of the vortex generated by a round jet and that of the vortex generated by a rectangular jet are studied numerically. In the calculation, the Reynolds Averaged Navier-Stokes equations with the Renormalization Group (RNG) based κ-ε turbulence model were used to analyze the incompressible flow field, and were solved using the commercial code FIDAP 7.6 which employed the Finite Element Method. The typical results are compared with the Zhang-Collins data. Further, the effects of jet parameters such as pitch angle and velocity ratio on the strength of the vortex generated by the jet are investigated.
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Nobuo OGAWA
Article type: Article
Pages
133-134
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Control of turbulent jets is required widely in industry fields, such as promotion of mixing of fluids and heat conduction and noise reduction etc. Some methods are considered for the control of turbulent jets, for example, methods of change of cross section of the nozzle and methods using the characteristics of flow fields in the jets. In this article the later is dealt for the control of the turbulent jets. That is, the methods of the control by means of tone and small nozzle are investigated which introduce the increase of diffusion due to stretching and brake down of the vortex tubes in the mixing layer of the jets. And the change of the fluctuating velocity of the flow fields due to the tone and the small jet is investigated by wavelet analysis.
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Akiko Sunaoka, Hiroshi Maekawa
Article type: Article
Pages
135-136
Published: July 31, 2000
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The development of an airfoil microactuator system for closed-loop control of vortex motions in a jet flow is presented in this paper. The oscillatory with a section of NACA0020 can manipulate a large-scale vortex ring at various frequencies lower/higher than the vortex ring generation. The microactuator performance is tested by means of flow visualization and measuring of velocity fluctuations. It is concluded that the actuator system indicates a valid procedure for jet flow control with the manipulation of vortex ring.
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Hidemasa MIYOSHI, Hideharu MAKITA, Nobumasa SEKISHITA, Yuuji YAMAGUCHI
Article type: Article
Pages
137-138
Published: July 31, 2000
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Coherent vortex structure was controlled by bimodal excitation in a two-dimensional jet. The scale of the symmetrical vortex structure was different in the nonlinear interference region. The growth of the subharmonic component was increased remarkably for Φ_<in>=0°, 300°, Φ_<in> is the phase difference between Strohal frequency and the subharmonic frequency. In the meantime, it was suppressed for Φ_<in>=120°. For Φ_<in>=300°, the vortex was merged until X/2H ≒8 in the excited intensity of ±1%, and until X/2H ≒6 in the excited intensity of ±2%. After the pairing, the vortex arrangement became anti-symmetric. The pairing of the vortex was not regularly generated for Φ_<in>=120°.
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Takahiro KIWATA, Atsushi OKAJIMA, Shigeo KIMURA, Kiyoteru ANDO
Article type: Article
Pages
139-140
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This paper describes the results of experimental studies concerning the near-field vortex structure and dynamics of a coaxial jet. The effect of excitation and circular jets on the vortical structure in the inner and outer shear-layer was studied. The flow visualization and the measurements of mean and fluctuating velocities by a hot-film probe and the particle image velocimetry (PIV) technique, were carried out in an open water tank. For the excitation of the initial vortex frequency, it is found that the vortex-pairing event is promoted by the forced by the forced excitation and it results in the rapid expansion of the jet width and the increase of velocity fluctuation and the entrainment rate. It is certified that the vortex-pairing event in the shear-layer is affected by the excitation of the relevant jet. For the velocity ratio near unity, the dominant peak frequency becomes the initial vortex frequency independent of the forced excitation frequency.
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Naofumi KUBO, Hideharu MAKITA, Mamoru SATO, Kazuhiko TANI
Article type: Article
Pages
141-142
Published: July 31, 2000
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Interaction phenomena between adjacent two horseshoe vortices were experimentally investigated. A pair of horseshoe vortices was artificially induced by injecting small swirling jets into the bottom of a fully developed turbulent boundary layer. Coherent velocity vector were obtained from the ensemble-averaged velocity components measured through the conditional sampling. When two horseshoe vortices developed downstream, they merged with each other. Merged horseshoe vortices generated M shaped structure and, finally, conformed a single larger horseshoe vortex. As these structures were stretched downstream, ejection and sweep were lined up along the symmetry plane of merged structure. In the lower boundary layer, high and low speed structures were aligned alternately in the spanwise direction.
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Yoshiyuki TSUJI, Kei MIYACHI, Takehiro KUSIDA, Ikuo NAKAMURA
Article type: Article
Pages
143-144
Published: July 31, 2000
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Tomoko IGARASHI, Yuji TAMURA, Yutaka OHTA
Article type: Article
Pages
145-146
Published: July 31, 2000
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The bursting structure of the turbulent boundary layer under a favorable pressure gradient is experimentally investigated using the continuous wavelet transformation and the variable-interval time averaging technique, abbreviated to VITA technique. By using Gabor function as the analyzing wavelet, ejection and sweep processes as well as the center of burst can be detected independently with high accuracy. The results show that the continuous wavelet transformation with complex mother wavelet function can be one of the most effective technique to investigate bursts in turbulent boundary layer. Furthermore, paying attention to the frequency region which the wavelet coefficient shows the maximum extreme, bursting can be classified approximately by its own time-scale, and bursting structures, such as bursting frequencies, duration of burst are investigated.
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Toshiro Kiura, Hiroshi Higuchi, Yasuaki Kohama
Article type: Article
Pages
147-148
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The irregular dynamic behavior of a knuckleball is believed to be caused by the seam and the asymmetrical flow separation. In the present experiment, the characteristic of the force acting on a baseball and the velocity vector fields in the wake were further correlated with the seam orientations of the baseball. The seam was identified to cause flow separation or boundary layer transition depending on its position. Hysteresis effect of the boundary layer separation as well as three-dimensional vortical wake structures were examined.
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Keizo AGARI, Kenkichi OHBA, Maiko MITSUKURI, Taisuke MORITA, Tomohiko ...
Article type: Article
Pages
149-150
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Aerodynamic forces on the NACA0012 aerofoil were measured and a flow visualization around it by smoke was made in a low Reynolds number region. Lift and drag force measurements were made using an external strain gage balance for a chord Reynolds numbers range of 2.0×(10)^4∿1.3×(10)^5. A flow visualization study at Re=1.3×(10)^4 was performed and correlated with the force measurements. We found that there were two patterns of vortex shedding : one was concerned with a trailing vortex winding up from the lower surface around the trailing edge in the region below 6 degree. The other was caused by Kelvin-Helmholtz instability in the region greater than 11 degree.
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Hiromichi MORIKAWA, Koh KATOH, Yutaka SATA, Tatsuo ARAKI
Article type: Article
Pages
151-152
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Particle Image Velocimetry (PIV) can measure whole flow field simultaneously without disturbing the flow field. One of PIV techniques, Two Dimensional Particle Tracking Velocimetry (2-DPTV) may show us accurate results, and it can analyze the visualized digital images at high speed. On the other hand, it is difficult to achieve high spatial resolution enough. Therefore we improved particle tracking algorithms. In our old tracking algorithms, particles are tracked over tree time-steps, but in new tracking algorithms, particles are tracked over four time-steps. Even if the particle density increases, new algorithms may track each particle accurately. Our new method was compared with our old one, and in order to check the effectiveness of particle tracking algorithms, we used the standard images provided by the PIV-STD Project of the Visualization Society of Japan.
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Shigeru MURATA, Norifumi YASUDA
Article type: Article
Pages
153-154
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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This paper presents a digital method for detecting the position of small particles distributed in 3-D space from in-line hologram patterns. The detection is carried out by numerically reconstructing the real image of the particles from observed hologram patterns. This method is called full volume digital holography in this paper because the real images are reconstructed in 3-D space over the full range of measurable depth. The measurement accuracy of the present method is evaluated in numerical simulation and experiment. It is shown in numerical simulation that the RMS error in depth is 0.55mm for the range from 200 to 300mm, and the experimental results also show the high measurement accuracy of the present method.
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Kenji KANAZAWA, Kenkichi OHBA
Article type: Article
Pages
155-156
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The waves generated on the liquid column surface were an important origin of the liquid column disintegration. Hence, the wave characteristics on the liquid column injected perpendicularly into an airstream were experimentally studied. The propagation velocity, the wavelength, and the amplitude of the wave were measured from the images by high-speed video camera with a speed of 40,500 frames per second. The propagation velocity of the wave near the liquid nozzle was almost same as the injection velocity. Although the injection velocities were varied, the wavelength and the amplitude of the wave near the liquid nozzle were kept almost constant, respectively.
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Hironori YAMADA, Tadayoshi SUGIMURA
Article type: Article
Pages
157-158
Published: July 31, 2000
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Toshio NAKAGAWA, Tadayoshi SUGIMURA
Article type: Article
Pages
159-160
Published: July 31, 2000
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Katsuine TABEI, Hiroyuki SHIRAI, Terutaka Daifuku, Humio TAKAKUSAKI
Article type: Article
Pages
161-162
Published: July 31, 2000
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Cavitation flows emit very weak light and it is closely related to bubble collapses and erosions. In order to obtain the relationship between erosion damage rates and luminescence intensities, erosion tests were performed for a water orifice-cavitation in a pipe flow. In the experiments, a copper plate was set a little downstream from an orifice in the pipe. Damage rates were evaluated by counting the number of damage pits, and luminous intensity was measured in an absolute unit by a photon counter at the wavelength of 450 nm. The number of damage pits was counted by an image processing method and a laser reflection method, too, besides a usual visual inspection method. An empirical formula for the relationship between the erosion and the luminescence intensity was presented.
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Keiichi SATO, Yasuhiro SAITO, Hirokazu NAKAMURA
Article type: Article
Pages
163-164
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Impulsive force based on the collapse of cavitation is an important problem for fluid machinery. Collapsing behavior in the separated shear-layer cavitation is known to be high impulsive, so it is investigated using a contraction and divergence tunnel. The impulsive force at the collapse of cavitation is detected using an accelerometer. In addition, cavity behaviors are investigated in detail using a high-speed-video-camera triggered by the accelerometer. As a result, it is reported that two characteristic patterns of bubble collapse are observed in relation to cavitation impact.
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Hiroyoshi MORISHIMA, Kenichi SANO, Mitsuo KONO
Article type: Article
Pages
165-166
Published: July 31, 2000
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Compressed air energy storage (CAES) systems are expected to be one of those systems equalizing the load of electricity generation. However hydraulically compensated CAES systems are supposed to be subject to an explosive instability such as "blow-out" of bubble flow caused by a champagne effect. This instability is a key notion for constructing efficient CAES systems. An insight into the mechanism of blow-out is gained by taking account of bubble dynamics. A system of basic equations for bubble flow has been derived by taking moments of the kinetic equation which is constructed based on dynamical equations of bubbles and is claimed as the first self-consistent closed system describing bubble flow. This report shows that steady solutions of one-dimensional vertical bubble flow has been analytically obtained, being confirmed by numerical solutions.
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Satoshi OGATA, Keizo WATANABE
Article type: Article
Pages
167-168
Published: July 31, 2000
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Recently, considerable interest has developed in surfactant additives for use in district heating and cooling systems to lower pumping energy requirement. We already reported the drag reduction for an enclosed rotating disk in surfactant solution. On the other hand, it is not cleared that the mechanism of the drag reduction for the frictional resistance of the rotating disk in surfactant solutions. In this study, it is clarified that the effects of surfactant additives on the flow around the rotating disk from flow visualization. Experiments were carried out by means of aluminum and tufts techniques. Test surfactant solution was Ethoquad O/12 with sodium salicylate at concentrations of 200ppm and temperature was 18℃. Consequently, it has been clarified that the amplitude of circular vortex over the rotating disk was reduced and the flow direction near the disk was turned to outward by the surfactant solution.
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Hidetoshi AKASHI, Noriyasu MORI, Kiyoji NAKAMURA
Article type: Article
Pages
169-170
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Mechanism of surface alignment of liquid crystals (LCs) on the films formed by coating with concentrated solutions of hydroxypropylcellulose (HPC) is studied using a model coating flow. The numerical simulations for the model coating flow are carried out using the Doi model for concentrated solutions of rod-like polymers. The development of molecular orientation on the free surface is revealed in the simulation. Furthermore, parallel surface alignment is obtained under the conditions of high coating speed and thin coating thickness in the experiment of the coating film. The experimental results are discussed in connection with the simulation ones.
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Yoshihiro KONDO, Shinji MATSUSHITA, Takashi MORIYAMA, Shigeo OHASHI
Article type: Article
Pages
171-172
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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We have developed a method of cooling high-power-density CPU modules within a bending duct. The method uses a jet-duct system made of an air duct and axial fans. This system has slit orifices upstream from the CPU modules. Pressure drops in this system are calculated as four values : wringing loss in the chamber, friction loss in the duct, extrusion loss from the duct, and wringing loss in the slit orifice. These loss values agree with the experimentally measured losses to within an error of ±10%. The calculation showed that when the duct width is small, the wringing loss in the chamber account for the major part of the total loss.
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Kiyoshi KAWAGUCHI, Tadayoshi TERAO, Eitaro TANAKA, Hiroshi TANAKA
Article type: Article
Pages
173-174
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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In recent years, CPU calorific power is increasing rapidly involved in computer high performance. So computer industry is requiring cooling unit for CPU correspond to high calorific power and heat flux. We have developed a new compact boiling refrigerant type cooling unit for CPU. It is the main feature of this cooling unit is high cooling performance, compact, and low electric power compared with air-cooling aluminum fin. We made the relation between behavior of coolant and cooling performance at inclination
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Kazuhiro FUKUYO
Article type: Article
Pages
175-176
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Takanori NAKAMURA, Koutarou TEZUKA, Yasuyuki ENOMOTO
Article type: Article
Pages
177-178
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
CONFERENCE PROCEEDINGS
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In order to clarify the distribution of hydraulic losses in a middle specific speed model pump-turbine, detailed measurements were conducted at runner outlet and each flow passage with two-dimensional LDV, high accuracy differential pressure transducers. Besides, it was made clear that the hydraulic loss between casing and guide vanes takes 50% to the total loss in pump operation. Moreover, it was confirmed that the method of loss analysis used in this study is entirely effective about the development of pump-turbine.
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Yuji ISHIHARA, Yuichi SAKUMA, Michitoshi TAKAGI
Article type: Article
Pages
179-180
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Unsteady pressure measurements were made at multiple locations in the intake system of a passenger car engine using equipment for measuring unsteady pressure at up to 256 spatial points and at frequencies up to 300 Hz. The engine used in this experiment was a four-cycle, four-cylinder engine displacing 1998 cubic centimeters and was driven by a chassis dynamometer. Pressure measurements were obtained at 104 points between the inlet of the air intake and the intake manifold. The results obtained were animated to visualize pressure fluctuations.
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Noboru KURIHARA, Yoshiya TERAO, Masaki TAKAMOTO
Article type: Article
Pages
181-182
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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An anemometer calibration system in the range of 3 to 30 m/s has been developed. This system consists of an LDV calibrator, an LDV for a transfer standard and a wind tunnel, which uses an ultrasonic anemometer installed on the side walls of the test section as a reference standard. An anemometer under test is placed at the center of the wind tunnel test section and the anemometer output is calibrated against the ultrasonic anemometer, which has been beforehand calibrated using the LDV, which is also calibrated by the LDV calibrator. Repeated tests of this system showed that precise adjustment of the LDV processor threshold level is necessary to avoid an error due to a misalignment of the LDV optics. It is also suggested that when the LDV is calibrated by using the LDV calibrator, the condition including the filter range and the threshold level should be set as same as possible to that used to calibrate the ultrasonic anemometer.
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Masafumi MIYATA, Ryushi YAGI
Article type: Article
Pages
183-184
Published: July 31, 2000
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 various velocity-ratios from 0.8 to 6. The penetrating length of the jet into the counterflowing stream depends only on the velocity-ratio and increases exactly linearly with it. The mean velocity and the turbulent intensity variations on the jet axis depend also only on the velocity-ratio. It is very interesting to know that the turbulent intensity on the jet axis, non-dimensionarized by the uniform counterflowing velocity, takes a maximum nearly at the stagnation point and the maximum has a constant value of 1 for velocity-ratios greater than 2. Surprisingly enough, measurements with a static tube show that the pressure difference from the ambient flow becomes zero at the stagnation point and is negative almost everywhere in the jet.
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Kazumi SUZUKAWA, Shinsuke MOCHIZUKI, Hideo OSAKA
Article type: Article
Pages
185-186
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Turbulent flow fields around two impellers, a standard four flat paddle-type impeller and the same type impeller with a hole at each blade, were investigated using by LDV. Mixing Reynolds number was 1.2×(10)^5. Power number was also measured with torque meter. Mixing vessel used was a closed cylindrical tank of 490mm diameter with a flat bottom and four vertical baffles. It can be found from the results that power number of the modified impeller was 8% lower than standard impeller, but total discharge flow rates were almost the same.
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Toshihiro TAKAMI, Yosinori KITA, Yasuhiro OTUDA
Article type: Article
Pages
187-188
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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Three-components of velocities and a wall shear stress have been measured using a non-orthogonal triple-sensors probe and a wall film sensor in unsteady turbulent pipe flows with stepwise time variations of flow rate imposed, whose timing schedule is programed by a PC. It is found that the response of turbulence is late compared with variation of flow rate, although the axial velocity shows similar distribution with the time variation of flow rate synchronized. Also, the unsteady turbulence structure has the same statistical property as that in the steady turbulent pipe flow.
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Masashi MATASUMOTO, Sadatake TOMIOKA, Naoshi KURATANI, Yuji IKEDA
Article type: Article
Pages
189-190
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The Pressure sensitive paint (PSP) technique was used to visualize the continuous surface oxygen concentration field around a sonic jet injected transversely into a supersonic freestream of Mach 2.4. The jet-to crossflow dynamic pressure ratios of approximately 0.7 was examined. The visualized flow field showed high concentration regions of the bow shock waves between the injectors affects the spreading and behavior of the horseshoe vortices, and the horseshoe vortices downstream of the injectors affect the surface oxygen concentration field.
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Kuniaki TOYODA
Article type: Article
Pages
191-192
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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The object of the preset study is to make clear the generating mechanism of snow smoke behind trucks running in winter season, and to obtain the basic ideas to prevent the generation of snow smoke. Since the visualization experiments in a wind tunnel suggest that the large-scale vortices behind a truck generate the snow smoke, the spoiler generating three-dimensional perturbation was attached under the truck to suppress the evolution of the large-scale vortices. The three-dimensional perturbation was very effective to break up the large-scale vortices, and the spoiler was a useful device to prevent the snow smoke. The spoiler was installed to a model truck and an actual truck, and the effect of the spoiler was checked by driving tests. The results show that the spoiler is very effective to suppress the large-scale vortices behind the trucks.
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Shinsuke MOCHIZUKI, Kazumi SUZUKAWA, Hideo OSAKA
Article type: Article
Pages
193-194
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
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A swirl turbulent flow driven by a circular jet was investigated experimentally. Measurement of mean velocity and Reynolds stresses were carried out with hot-wire anemometers and a crossed hot-wire probe. In velocity vector and contour map of statistical quantities, the circular jet to be momentum source for the swirl flow is surrounded and distorted by secondary flow that is similar as seen for a jet in cross flow. External forces including the radial momentum equation were evaluated from experimental data. It is found that centrifugal force plays a dominant role on the trajectory of the jet.
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Kouhei IZUCHI, Ikuhiro OHYA, Nobuyuki OHKURA, Hidetoshi HAYAFUJI, Mune ...
Article type: Article
Pages
195-196
Published: July 31, 2000
Released on J-STAGE: August 01, 2017
CONFERENCE PROCEEDINGS
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The structure of a vortex ring in deformation process were investigated by means of smoke visualization technique. The photographs of the flow pattern of a section perpendicular to the axis of a vortex ring were taken continuously with a high-speed video camera. The solid picture of a vortex ring was obtained by constructing these photographs with a computer graphics tool. As the vortex ring travelled downstream, the circumferential distortion of a solid picture appeared regularly on its surface and grew into the polygon. At final stage, i.e., just before collapse of the vortex ring, it seemed that a pair of rings might enclose the vortex core of vortex ring. These pair of rings were not combined with the vortex core. The pair of rings may be constructed of a small pair of vortex ring which are generated due to the centrifugal instability.
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