JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 38 , Issue 3
Showing 1-21 articles out of 21 articles from the selected issue
  • Gabi Ben-Dor
    1995 Volume 38 Issue 3 Pages 325-334
    Published: August 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Based on recent analytical, experimental and numerical studies, a new state-of-the-art of oblique-shock-wave reflections in steady flows has been established. The main findings of these analytical, experimental and numerical studies are summarized. The recently established state-of-the-art is summarized in the conclusion section of this review article.
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  • Ikuo Nakamura, Yoshiyuki Tsuji
    1995 Volume 38 Issue 3 Pages 335-345
    Published: August 15, 1995
    Released: February 18, 2008
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    Four topics concerning the coherent structures of the turbulent boundary are discussed in this brief review. Firstly comments are given on the identification of C. S. (coherent structure), secondly some dynamical models of C. S. are surveyed, thirdly our recent study of the fractal nature of C. S. is summarized and an intimate relationship between the burst and the fractality is clarified, and finally some preliminary discussions are presented concerning the application of Kullback-divergence to turbulent flow.
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  • Min Lee Gyoo, Tsutomu Murakami, Michio Nishida
    1995 Volume 38 Issue 3 Pages 346-352
    Published: August 15, 1995
    Released: February 18, 2008
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    The present paper describes the numerical and experimental results on unsteady nozzle flows induced by nonstationary shock waves. The two-dimensional Navier-Stokes equations are numerically solved using the upwind TVD finite-difference scheme of the Harten-Yee type. For the purpose of computational visualization of shock waves in transient nozzle starting process, computer shadowgraphs are developed based on the principle of the optical shadowgraph. Visualization experiments employing a conventional shock tube are also performed. Comparison of numerical and experimental results shows satisfactory agreement. Furthermore, the steady flow establishment process around an airfoil model installed inside the nozzle is numerically investigated. The simulated results successfully reveal the unsteady viscous flow structure around the model.
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  • Tadayoshi Sugimura
    1995 Volume 38 Issue 3 Pages 353-359
    Published: August 15, 1995
    Released: February 18, 2008
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    Interaction between detonation and Prandtl-Meyer expansion is an interesting problem to be solved in connection with the disappearance or continuance of the fish-scale pattern. In this study, seven kinds of reflection nozzles were utilized in order to produce the Prandtl-Meyer expansion effects at various levels. Stability and behavior of a detonation propagating in a reflection nozzle attached to a parallel channel part were experimentally observed with the initial pressure as a parameter using optical measurement methods such as open-shutter and schlieren photographic techniques. It was found that in the case of a nozzle at the half-vertical angle of A = 18 degrees without the throat length, an initial pressure of at least 5. 3 kPa is necessary to sustain detonation configuration during passage through this nozzle.
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  • Makoto Momoi, Tatsuo Sawada, Takahiko Tanahashi
    1995 Volume 38 Issue 3 Pages 360-365
    Published: August 15, 1995
    Released: February 18, 2008
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    We experimentally studied shear flow of a water-based magnetic fluid between concentric annuli. The experiment was carried out by changing the angular velocity of the outer cylinder, and the moment acting on the inner cylinder was measured. Experimental results were discussed in the following three ways. At first the magnetic fluid was treated as a Newtonian fluid, and a small difference in the flow curves was found. Next the power-law fluid theory was applied in order to explain these differences. Finally we examined this flow problem using the micropolar theory, which gives the theoretical relation between the moment acting on the inner cylinder and the angular velocity of the outer one. We measured the coefficient which denoted the micropolar effect, and showed the influence of the substructure on the fluid.
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  • Naoyuki Kayukawa
    1995 Volume 38 Issue 3 Pages 366-373
    Published: August 15, 1995
    Released: February 18, 2008
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    The effects of the spatiotemporal inhomogeneity of a plasma in thermal equilibrium on the local and output characteristics of a Faraday-type MHD generator were investigated using numerically modeled turbulent velocity and temperature data. The conditions of Saha equilibrium in the range of the mean temperature level and the maximum turbulent frequency were given. The mean conductivity formula was also given as a function of the rms fluctuation. The average correlations between the electric field fluctuations and those of the conductivity in the mean Ohm's law were evaluated in terms of the mean electrical parameters. Rosa's G-factor was modified to include the spatiotemporal conductivity variance. It was shown that the one-dimensional anisotropic model somewhat underestimates the effective resistance of the turbulent MHD plasma with a two-dimensional anisotropy.
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  • Yoshiatsu Oki, Takahiko Tanahashi
    1995 Volume 38 Issue 3 Pages 374-381
    Published: August 15, 1995
    Released: February 18, 2008
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    The applications of MHD (magnetohydrodynamics) devices have been rapidly developed in recent years. Thermoelectrically conducting fluid has been increasingly used in the manufacturing process of semiconducting materials such as silicon crystal. In the present paper, we propose a new GSMAC (generalized simplified marker and cell)finite-element method coupled with the B method. The present scheme efficiently satisfies both conservation laws of mass and magnetic flux. In order to verify the present scheme, we discuss the natural convection of thermoelectrically conducting fluids in a square cavity under a uniform magnetic field. The numerical results obtained here agreed well with previous experimental and numerical results. Moreover, we estimate the effect of the induced heating term on a temperature field.
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  • Jun Ishimoto, Masaaki Okubo, Shinichi Kamiyama, Masaru Higashitani
    1995 Volume 38 Issue 3 Pages 382-387
    Published: August 15, 1995
    Released: February 18, 2008
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    Experimental study is made to clarify the effects of nonuniform magnetic field on bubble behavior in a magnetic fluid. The behavior of vapor bubbles is visualized with ultrasonic wave echo under the nonuniform magnetic field. It is found that the void fraction in two-phase flow decreases with increase in the magnetic field due to the effect of magnetic body force. Furthermore, the effects of nonuniform magnetic field on translational motion and deformation of a single gas bubble in a magnetic fluid are experimentally examined using a transparent thin duct, called a Hele-Shaw cell. The experimental results indicate that a single bubble is decelerated in the region of positive magnetic field gradient and accelerated in the region of negative magnetic field gradient, and that it is elongated in the direction of the magnetic field.
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  • Shuji Tanaka, Susumu Murata
    1995 Volume 38 Issue 3 Pages 388-397
    Published: August 15, 1995
    Released: February 18, 2008
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    Laser doppler velocimeter (LDV) measurements of velocity fields and the determination of static pressure distributions in the rotors of cross flow fans with good geometrical similarity but different dimensions have been performed, and the peculiar scale effects appearing in the flow details have been shown. The internal flow fields tend to be more active with increasing rotor size, and normalized velocity, vorticity, velocity fluctuations and pressure drops in the eccentric vortex increase as the fan dimensions increase. The mechanisms of generation and dissipation of vorticity in the eccentric vortex in rotor have been discussed, and it is suggested that the scale effects may be attributed to differences in the rate of diffusion of the circulation vortices in the recirculatory region. By analyzing the influences of Reynolds number and fan dimensions on performance curves, a new procedure for representing the performance of cross flow fans in a universal form has been proposed.
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  • Tamotsu Igarashi, Susumu Inagaki
    1995 Volume 38 Issue 3 Pages 398-403
    Published: August 15, 1995
    Released: February 18, 2008
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    Concerning the vortex shedder used for the Karman vortex flowmeter, the flow resistances of cylindrical bodies of various cross-sections in a circular pipe are given by the general equation in the previous works of Igarashi et al. In the present paper, it is confirmed that the equation is applicable to the vortex shedder having a low opening ratio. Then, the same idea is applied to the hydraulic losses of flow control devices asymmetrical to the cross-section of the pipe, such as a sluice valve, a butterfly valve and a cock. Consequently, these hydraulic losses are expressed by the following general equation : ζ=C[(1-β)/β2]n, where β is the opening ratio.
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  • Junichiro Fukutomi, Yoshiyuki Nakase, Masashi Ichimiya, Hirohito Ebisu
    1995 Volume 38 Issue 3 Pages 404-410
    Published: August 15, 1995
    Released: February 18, 2008
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    The internal flow in a cross-flow turbine is nonuniform because the water passes through only part of the runner. Therefore, the unsteady fluid forces act on a blade through rotation. Experimental and theoretical studies for determination of fluid forces on the blade in a cross-flow turbine are conducted. In the experiment, the tangential and radial forces are measured on a test blade using strain gauges and slip rings. On the other hand, in the theoretical study, they are calculated numerically using the unsteady momentum theory. The calculated results are compared with experimental data and good agreement is demonstrated. Furthermore, the maximum forces are found to occur immediately before the blade leaves the nozzle exit in both the experimental and theoretical results.
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  • Hirofumi Doi, Shojiro Kaji
    1995 Volume 38 Issue 3 Pages 411-418
    Published: August 15, 1995
    Released: February 18, 2008
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    Unstarted supersonic flutter in a cascade is characterized by the existence of detached bow shock waves ahead of leading edges of the blades. The oscillating cascaded blades accompanied by the detached bow shock waves are analyzed based on the semiactuator disk theory. The effect of the detached bow shock waves on the stability of blade oscillation in a bending mode with interblade phase angle is investigated, in consideration of the pressure wave reflected at the shock wave surface and the vorticity wave and entropy wave generated by the oscillation of the shock wave and blades. The results show that the detached bow shock waves greatly destabilize the blade oscillation in bending mode, and the flutter boundary markedly extends to a high-frequency region.
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  • Hiroyuki Hashimoto, Akio Ihara, Rokuro Sato, Hideo Watanabe, Hirokuni ...
    1995 Volume 38 Issue 3 Pages 419-425
    Published: August 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A newly developed pumping system is presented. The pumping effect was experimentally obtained using a vibrating choke nozzle in a stationary liquid. The relation-ship between pump performance and the input vibration conditions was investigated. By the flow visualization of inflow and outflow bubbles, the flow mechanism in the actual pump operation was investigated. It has been confirmed that this pumping effect can be utilized in actual pump machinery.
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  • Long Zhang, Takahiro Ueda, Toshiaki Takatsuki, Katsuhiko Yokota
    1995 Volume 38 Issue 3 Pages 426-431
    Published: August 15, 1995
    Released: February 18, 2008
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    An experimental study investigating the cyclic variation of the internal air motion has been conducted in a motored engine having a cup-in-piston combustion chamber. The engine used for this study has a transparent quartz liner and a transparent acryl piston. The continuous wave beam of a 4 watt argon ion laser was formed into a thin light sheet to define the measurement plane. The scattered light from the particles which were supplied to the intake air stream, were recorded by a NAC E-10 high-speed camera and the bulk flow fields inside the combustion chamber were measured at planes parallel and perpendicular to the piston crown by means of an image processing technique. We reveal, for the first time, continuous cycle-resolved two-dimensional bulk flow fields inside the combustion chamber around the compression TDC. Also, comparison between cycle-resolved and ensemble-averaged flow patterns has shown that the latter may become artificial ones if there exists a strong effect of cyclic variation. Moreover, by examining the rms of the variation component and the ratios of the rms to ensemble-averaged velocity with and without swirl, it is found that the ratios of the rms to ensemble-averaged velocity can be used for evaluating the effect of the cyclic variation on the flow fields.
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  • Hiroyuki Takahira, Soichiro Yamane, Teruaki Akamatsu
    1995 Volume 38 Issue 3 Pages 432-439
    Published: August 15, 1995
    Released: February 18, 2008
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    This paper deals numerically with nonlinear oscillations of spherical bubbles in a sound field. A Governing equation of a cluster of interacting spherical bubbles is obtained by taking account of the compressibility of a liquid. This equation includes previous results for both single bubble and two bubbles as special cases. Bifurcation diagrams are computed for typical configurations of bubbles. It is shown that the bifurcation structure of multiple bubbles with the same radii which are arrayed symmetrically in a sound field is similar to that of an isolated bubble driven by sound of higher frequency. When bubbles with different initial radii oscillate in a sound field, the independent oscillation of each bubble is suppressed by bubble interactions and the bubbles take on a collective behavior.
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  • Yasushige Hirata, Masayuki Takano, Tsutomu Narasaka
    1995 Volume 38 Issue 3 Pages 440-447
    Published: August 15, 1995
    Released: February 18, 2008
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    In order to establish an accurate measurement method for simultaneous measurements of flow rates Q and particle concentrations Cv in heterogeneous solid-water two-phase flows, the pressure-drop ratios were investigated in detail at the exit of a typical Hershel-type venturi in both horizontal and vertical pipe arrangements for six different kinds of solid-water flows with various Q and Cv. The results were represented by a simple formula similarly to that in our previous report on throat measurements. These results obtained at the exit, together with those obtained at the throat, indicated the possibility of simultaneous measurements of Q and Cv in an easy and accurate manner by means of only one Venturi.
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  • Ru Hung J., Hai Pan L.
    1995 Volume 38 Issue 3 Pages 448-457
    Published: August 15, 1995
    Released: February 18, 2008
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    The mathematical formulations of orbiting spacecraft sloshing dynamics for a partially filled liquid of cryogenic superfluid helium II in a Dewar container driven by the gravity gradient acceleration associated with slew motion are studied. The Advanced X-ray Astrophysics Facility-Spectroscopy (AXAF-S) spacecraft is chosen as a practical example in this study. Explicit mathematical expressions for the orbital gravity gradient acceleration associated with the slew motion acting on spacecraft fluid systems are derived. The numerical computation of sloshing dynamics is based on the non-inertia frame spacecraft bound coordinate and the solution of time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions which treat the capillary force effect of sloshing dynamics on the liquid-vapor interface in a microgravity environment are also derived. This study discloses the capillary force effect of sloshing dynamics that governs liquid-vapor interface fluctuations driven by the gravity gradient acceleration associated with slew motion. This sloshing dynamics affects the stability of the orbital spacecraft fluid system in a microgravity environment.
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  • Yoshitaka Sakamura, Michio Nishida
    1995 Volume 38 Issue 3 Pages 458-464
    Published: August 15, 1995
    Released: February 18, 2008
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    In this paper, an efficient and robust implicit scheme for the calculations of thermochemical nonequilibrium flows is presented. In the implicit operator, approximations for the inviscid flux Jacobians and the thermochemical source term Jacobian are used in order to avoid matrix inversions and to eliminate the strong nonlinearity of the thermochemical source term. The residual is spatially discretized using a MUSCL-type, finite volume formulation. The inviscid fluxes at cell interfaces are evaluated by van Leer's flux-vector splitting method extended to incorporate thermochemical nonequilibrium. Numerical results show that the scheme is so robust that very large sizes of time steps are allowed in spite of stiffness caused by thermochemical source terms. Furthermore, the results show the importance of the effective cross section of the vibrational excitation, σvib, in the thermochemical nonequilibrium flow calculations.
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  • Hiroyuki Nagaki, Koji Korematsu
    1995 Volume 38 Issue 3 Pages 465-474
    Published: August 15, 1995
    Released: February 18, 2008
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    In both spark ignition engines and diesel engines, exhaust gas recirculation (EGR) is well known as an effective technique to reduce emissions of nitrogen oxides. However, it has not yet been applied practically to heavy-duty diesel engines because the wear on piston rings and cylinder liners is increased by EGR. It is widely accepted that sulfur dioxide in burnt gas is strongly related to this wear increase. This paper proposes a numerical model to clarify the mechanism of wear which estimates the amount of sulfur dioxide absorbed by lubricating oil film. The calculated results show that the concentration of sulfur dioxide in lubricating oil film is increased with the increase in the rate of EGR and the reduction in engine speed, and is decreased with the decrease in engine load. The measured amount of wear on piston rings and cylinder liners is related to the concentration of sulfur dioxide in lubricating oil film.
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  • Norimasa Iida, Kei Watanabe, Hideki Ohashi
    1995 Volume 38 Issue 3 Pages 475-482
    Published: August 15, 1995
    Released: February 18, 2008
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    A single-action rapid compression machine was developed to observe soot formation and oxidation processes in a diesel spray flame. The two-color method was applied to analyze the flame temperature and KL factor from the flame image taken by a high-speed camera. Variation in the surrounding gas-oxygen concentration was achieved by adding differing quantities of pure oxygen, nitrogen, carbon dioxide and argon gases when charging air, ranging from 17 to 25 vo1% of oxygen concentration, to examine the effect of flame temperature. The initial gas temperature has a great effect not only on ignition delay but also on soot formation speed. Higher oxygen concentration resulted in higher flame temperature and faster soot oxidation speed in the flame. Carbon dioxide has a soot-reduction effect in spite of its lower flame temperature.
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  • Takuji Ishiyama, Kei Miwa, Osamu Horikoshi
    1995 Volume 38 Issue 3 Pages 483-489
    Published: August 15, 1995
    Released: February 18, 2008
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    The main theme of this study is to reveal the characteristics of the fuel-air mixture that is responsible for ignition of diesel sprays. For this purpose, the ignition process of a spray was studied under diesel-like conditions realized by a rapid compression machine. The fuel-air mixture before ignition was chemically analyzed by a total gas sampling method. The condition to which fuel was subjected was estimated by combining the information on the mixture composition with pressure-time curves and photographs of sprays. The results show that the mixture before ignition has considerably higher temperature than the surrounding air. Oxidation begins very early in the ignition delay period, which supplies heat to the spray and causes cracking and gasification of fuel. It is assumed that the accumulated gas begins to release a large amount of heat triggered by the oxidation of a relatively small-scale mixture.
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