Transactions of the Japan Society of Mechanical Engineers Series B
Online ISSN : 1884-8346
Print ISSN : 0387-5016
Volume 65, Issue 633
Displaying 1-48 of 48 articles from this issue
  • Hitoshi SUGIYAMA, Mitsunobu AKIYAMA, Norifumi KOIDE
    1999 Volume 65 Issue 633 Pages 1505-1512
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A numerical analysis has been performed for developing turbulent flow of non-Newtonian fluid in curved pipe, Numerical results are shown in two cases of power-law fluids, i.e. power index 0.76 and 0.9, at Reynolds number 19000. The ratio of bend mean radius of curvature to radius is 10 and straight duct of 40 and 100 diameters are attached to the inlet and outlet of the bend, respectively. In numerical analysis, an algebraic Reynolds stress model was adopted in order to predict precisely the anisotropic turbulent flow and boundary-fitted coordinate system was introduced as the method of coordinate transformation. The numerical results are compared with the experimental data measured by laser-Doppler anemometer. Mean velocity and fluctuating velocity in axial direction are examined into detail to clarify the validity of the turbulent model and present numerical method. As a result of this research, it is found that the present method could predict well the streamwise mean-velocity in both cases of power-law fluids. As for the comparison of fluctuating velocity, characteristic features are reproduced except for the outer region of pipes. The present method predicts its value in outer regin smaller than that of the experiment, while the present method realized the phenomenon of decaying mean fluctuating velocity with decreasing power index. The results of comparison with the experimental data suggest that algebraic turbulent model is applicable to the non-Nowtonian fluid although agreement between both results is certainly not perfect in all detail.
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  • Masatoshi KODERA, Yasutaka IGARASHI, Kazuhiro NAKAHASHI, Takeshi KANDA ...
    1999 Volume 65 Issue 633 Pages 1513-1519
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Computations of internal viscous flow fields of scramjet models were conducted at inflow Mach number of 3.4 and 5.45. An unstructured hybrid grid method was used to compute the scramjet models with and without a short strut. The numerical method to solve the Navier-Stokes equations on the hybrid grid was developed using a finite volume cell vertex scheme and the LU-SGS implicit time integration algorithm. The computational results revealed that a thick subsonic region did not exist in the combustor near the top wall at Mach number 5.45. It was a favorable feature to avoid the engine unstart. With the strut, relatively low velocity regions became larger and the down wash flow toward the cowl behind the step became strong. The overconcentration of the fuel toward the top wall during the weak combustion was found in the experiment. The reason of it was realized that the airflow near the injector was turned to the top wall due to the small influence by the combustion in the experiment.
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  • Syusaku HARADA, Toshitsugu TANAKA, Yutaka TSUJI
    1999 Volume 65 Issue 633 Pages 1520-1527
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A numerical analysis of incompressive flow around a solid cylinder which falls to a solid wall was performed to study the effect of fluid on the interaction between solid bodies. A time-dependent boundary-fitted coordinate system and a transformable grid which moves arbitrarily were adopted in order to express unsteady and relative motion of solid boundaries. The fluid force acting on the cylinder was calculated directly by integrating the stress and the pressure on the surface without using any models. The effect of the induced pressure on the behavier of the cylinder was studied, and the results were compared with the analytical theory of lubrication. The obtained pressure in the gap showed similar profiles to the one derived from the lubrication theory. Furthermore, it was studied about dominant effects on the motion of the cylinder in the fluid, especially about the effect of the unsteady motion of the cylinder. In addition, it was examined the effect of the inclination of the wall to the motion of the cylinder.
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  • Yasuhiko NAKANISHI, Keishi GOTOH, Kiyoyuki NAKAGAWA, Koshi MITACHI
    1999 Volume 65 Issue 633 Pages 1528-1534
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Distinct element method (DEM) proposed by Cundal and Strack is useful for simulating behavior of particle beds. However, the results of the simulation differ from the experiment in general Although the rolling friction should be taken into account, it is usually ignored in the existing DFM, so that for instance, a single particle rolling on a horizontal plate keeps unreally constant velocity without deceleration. This paper proposes to take account of the rolling friction generated by the elastic hysteresis of particles in the existing DEM. A particle bed in a rotating horizontal cylinder is chosen as a testing model for the numerical simulation to examine the DEM improved in this paper by introducing the rolling friction. The present DEM can explain the rolling, cascading and cataracting flow modes of the particle bed, while the existing DEM cannot do except the rolling mode.
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  • Hiroshige KUMAMARU, Kenji OGITA, Yoshiki FUJIWARA
    1999 Volume 65 Issue 633 Pages 1535-1541
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Numerical calculations have been performed on magnetohydrodynamic (MHD) two-phase annular flow in a rectangular channel with a small aspect ratio, i.e. a small ratio of the channel side perpendicular to the applied magnetic field and the side parallel to the field. Results of the present calculation agree nearly with Inoue et al.'s experimental results in the region of large liquid Reynolds numbers and large Hartmann numbers. Calculation results also show that the pressure drop ratio, i.e. the ratio of pressure drop of two-phase flow to that of single-phase flow under the same liquid flow rate and applied magnetic field, becomes lower than ∼0.02 for conditions of a fusion reactor plant.
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  • Hidetaka OKUI, Myeong Kwan PARK, Shuzo OSHIMA, Ryuichiro YAMANE
    1999 Volume 65 Issue 633 Pages 1542-1550
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    As the basic study of the passive control of the shock oscillation, steady pseudo shock in the rectangular ducts with the porous wall and the bypass system was investigated experimentally and numerically. The expriments were carried out in a blow-down supersonic wind tunnel at a free stream Mach number of 2.0. Numerical simulations were made with the 2-D compressible Navier Stokes code. In sloving the equations, 2nd-order accurate Harten-Yee's upwind TVD scheme and κ-ε turbulence model were used. It is shown that the boundary layer thickness under the first shock wave of the pseudo-shock is controlled by the passive control method without noticeable changes of the pseudo-shock strcuture. But the total pressure loss downstream of the pseudo-shock is reduced by this method. And the effects of some parameters influencing the passive control method are studied numerically.
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  • Yoshiyuki WAKI, Takuji ISHIKAWA, Shuzo OSHIMA, Ryuichiro YAMANE, Motoh ...
    1999 Volume 65 Issue 633 Pages 1551-1558
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    It is pointed out that mass accumulation in an artery, such as LDL accumulation, influences the progression of stenosis severely. Mass accumulation in pulsatile blood flow through a stenosed artery is analyzed numerically. Flow is assumed to be periodic and axisymmetric. Non-Newtonian viscosity of blood and movement of arterial wall are considered. The effect of intermittency, pulsation and wall movement on mass accumulation is investigated. Flow pattern, concentration pattern and distribution of mass accumulation on the wall are obtained. It is found that mass accumulates particularly just upstream and downstream of stenosis. Therefore, it is suggested that the flow structure around stenosis is closely related to mass accumulation just upstream and downstream of stenosis. Mass accumulation decreases at stenosis and increases downstream of stenosis due to wall movement.
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  • Tetsuya KOGAKI, Toshio KOBAYASHI, Nobuyuki TANIGUCHI
    1999 Volume 65 Issue 633 Pages 1559-1567
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    In order to conduct direct numerical simulation (DNS) or large eddy simulation (LES) of turbulent flows in complicated flow geometry, accurate finite difference methods are needed in generalized curvilinear coordinate system. Recently, it was shown that the analytical conservation properties of the set of basic equations are needed to be satisfied properly even in discretized basic equations in order to obtain accurate and stable solutions in simulations of incompressible turbulent flow using finite difference method. The basic equations treated here are the continuity equation, the Navier-Stokes equation and the transport equations of the square values of velocity components and the kinetic energy. In this paper, finite difference schemes in generalized curvilinear coordinate system that are suitable for simulations of incompressible turbulent flow are constructed from relatively simple extension of the proper finite difference schemes derived in equidistant Cartesian coordinate system. The extension of finite difference scheme into generalized curvilinear coordinate system is based on the fact that the analytical conservation properties of the coordinate transformed basic equations for incompressible viscous flows are identical with that in Cartesian coordinates.
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  • Tetsuya KOGAKI, Toshio KOBAYASHI, Nobuyuki TANIGUCHI
    1999 Volume 65 Issue 633 Pages 1568-1576
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    In this second report, the conservation properties of finite difference schemes in generalized curvilinear coordinate system constructed in the first report are examined by numerical tests of two-dimensional inviscid flow with periodic domains. It is confirmed that the modified finite difference scheme in a colocated grid layout conserves the mass and kinetic energy properly even in nonorthogonal nonuniform computational grid. The conservation properties of the finite difference scheme in a staggered grid layout are also proper only when computational grids are orthogonal. In addition, direct numerical simulations of a plane channel flow with fairly coarse mesh at Reτ-180 are conducted using the finite difference schemes in generalized curvilinear coordinate system. It is found that the mesh dependency such as nonorthogonality and nonuniformity on results is reduced by the modified finite difference schemes in the colocated grid layout.
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  • Daisuke HITOMI, Mitsunobu AKIYAMA, Hitoshi SUGIYAMA
    1999 Volume 65 Issue 633 Pages 1577-1584
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    In this study, numerical analysis has been performed to clarify the assessment of volume tracking algorithms in a three-dimensional flow field dominated by surface tension. The FLAIR method has been extended to three-dimensional problems in this study. The distinct feature of FLAIR developed in two-dimension is that the slope of line segment is estimated based only on two neighboring volume fractions. This feature is also adopted in the three-dimensional FLAIR method proposed in this study, even if the three-dimensional slope of interface is neglected. This three-dimensional FLAIR is applied to a non-straining flow field and a surface tension dominated flow field. The results are compared with those of the donor-acceptor method, the SURFER method and the CIP method with digitization. Consequently, it has been found that the precision of translation of interface is much more improved by the use of the CIP method with digitization and the three-dimensional FLAIR method than that of the other methods. However, the CIP method with digitization will produce an uneven interface.
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  • Yoshinori NAKAYAMA, Haruki TAKEGAHARA
    1999 Volume 65 Issue 633 Pages 1585-1590
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Conventional DSMC method analysis requires huge execution time in spite of its simple calculation method and use of high performance computer. This is because its analysis code has low vectorization ratio. In order to improve the vectorization ratio, in this study, the following ideas were introduced to the code : (1) random access array for particle registration to cell, (2) virtual boundary cell, (3) modification of flow-into and flow-out particle management and (4) lumpgeneration and storage of random numbers. Requiring large memory capacity, these ideas can avoid the execution of recursive procedures and improve the calculation efficiency. As a results, it was confirmed that the vectorization ratio was significantly improved (approximately from 18% to 94%) and the execution time was drastically reduced (acceleration ratio : approximately 11.3). It seems that this code contributes the computing load reduction of rarefied gas flow analysis.
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  • Osamu KITAMURA, Makoto YAMAMOTO
    1999 Volume 65 Issue 633 Pages 1591-1598
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A Reynolds stress model for predicting gas-particle two-phase turbulent flows has been developed in order to take account of the interactions between dispersed particles and fluid turbulence. The effects of dispersed particles on turbulence are added to the Reynolds stress model for single-phase turbulent flows. The model coefficients have been determined by using the experimental data of a gas-particle round jet and a fully-developed vertical pipe flow. The proposed model can satisfactorily reproduce the experimental data of both mean flow and turbulent properties. Finally, the model has been applied to a gas particle two phase turbulent swirling flow in order to investigate the model performance. The predictions show good agreement with the measurements in the case.
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  • Masakuni MURAMATSU, Takashi NAGATANI
    1999 Volume 65 Issue 633 Pages 1599-1606
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A traffic jam induced by slowing down is investigated using simulation techniques of molecular dynamics. When cars are decelerated by the presence of hindrance, two typical traffic jams occur behind the hindrance : one is an oscillating jam and the other is a homogeneous jam. When the slowing down is small, the oscillating jam occurs. If the slowing down is large, the jam is homogeneous over space and time. Also, a backward propagating soliton-like jam is observed. The linear stability theory is applied to the traffic flow. The phase boundary between the oscillating and homogeneous jams is compared with the neutral stability line obtained by the linear stability theory.
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  • Takeo KAJISHIMA
    1999 Volume 65 Issue 633 Pages 1607-1612
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    To improve the numerical simulation of incompressible fluid flow using rectangular grids of non-uniform spacings, a fully consistent and conservative finite-difference method is proposed for the convection term of Navier-Stokes equation of motion. When the mass continuity is satisfied numerically, the present schemes have complete conpatibility between the divergence form and the gradient form. In addition, the kinetic energy is conserved numerically according to the condition. These properties are evaluated by the numerical examples for laminar flow in a square cavity.
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  • Yutaka MIYAKE, Koichi TSUJIMOTO, Yasuaki AGATA
    1999 Volume 65 Issue 633 Pages 1613-1620
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A Direct Numerical Simulation (DNS) is conducted for a turbulent flow in a channel having a rough wall and a smooth wall. Rough wall is modelized by roughness elements represented by zero-volume wall-normal lines projected from the wall surface to around 15∼30 in wall unit which generate Stokes drag to the local flow. Global Reynolds number based on the mean friction velocities on two walls and channel half width is 400. It is intended here to demonstrate the validity of the roughness model, comparing the obtained flow with available experiments. It was confirmed that the model reproduces the experimentally obtained mean flow satisfactorily and that turbulence modification by roughness above the layer of roughness elements is qualitaively coincident with experiments.
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  • Masaaki TAMAGAWA, Takashi SANO, Teruaki AKAMATSU
    1999 Volume 65 Issue 633 Pages 1621-1628
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    This paper describes the particle inertia and the contact with the wall of red blood cells on the variance of particle path, that should depend on the hemolysis properties. The new methods of examining the inertia of red blood cells (particle) on particle path are discussed using computational fluid dynamics (CFD). In this method, the particles are moved by Stokes drag including effects of difference between density of plasma and internal liquid in the blood. The results of analysis by this method show that (1) the diameter of the particle (red blood cell) that means inertia of the cells, (2) the configuration of the objective wall boundary are important factor. These results also show that if the inertia and the contact with the wall are considered, the precision of the prediction of the hemolysis properties will be progressed.
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  • Koichiro OGATA, Katsuya FUNATSU, Yuji TOMITA
    1999 Volume 65 Issue 633 Pages 1629-1635
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Characteristics of free falling powder jet of glass beads of about 450μm diameter issuing from circuler orifices of 4, 6 and 8 mm are experimentally investigated by using a laser-Doppler velocimeter in terms of axial velocity profile for several distances between 1 mm to 1500 mm from the orifice. The velocity of particles is larger than the free falling velocity of the single particle υtl and increases with an increase in the mass flow rate. There exists a potential like profile near the orifice. At a long distance from the orifice, the profile relative to υtl is similar to that of single phase free turbulent jet, while the outer part is nearly truncated by υtl. The spread of the powder jet is very small as compared with the single phase jet. The entrained gas flow rate by the powder jet is predicted by assuming that the particle velocity is the sum of the entrained gas velocity and υtl, the result being compared with previous several models.
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  • Hiroyuki TAKAHIRA, Manabu SHIRASAWA, Shinji YAMASAKI
    1999 Volume 65 Issue 633 Pages 1636-1642
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    We develop a laser trapping method in order to control the position of bubbles out of contact. In this method, a thin laser beam that is scanned so as to trace a corn is focused into the liquid by using an immersion objective lens or a dry objective lens. This method is adequate to trap a rising bubble because the potential barrier made by the light momentum change due to the reflection and refraction on the bubble surface exists only at the upper side of the bubble. Moreover, the usage of the dry objective lens with large working distance has an advantage that the influence of the lens on the bubble is negligible because the objective lens can be set up outside the liquid. Bubbles of the order of 10 μm in diameter have been trapped and manipulated successfully by using the dry objective lens as well as the immersion objective lens. We also evaluate the optical force acting on a bubble both experimentally and theoretically. Trajectories of rising bubbles are predicted by taking account of the optical force. It is shown that the optical force in the lateral direction is weaker than that in the axial direction.
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  • Seiichi WASHIO, Satoshi TAKAHASHI, Yasuhiro UDA, Takumi SUNAHARA
    1999 Volume 65 Issue 633 Pages 1643-1651
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    It has been known that the traditional "nucleus" theory for cavitation is incompatible with some physically and experimentally recognized facts. In order to re-examine the issue cavitation in a hydraulic oil flow through a long two-dimensional acrylic constriction has been observed by strobos-copic photography with a microscope, laser beam transmission and pressure and noise measurements. A revelation was that at the very incipient stage of cavitation, a microscopic cavity suddenly emerges and attaches on the inlet edge. Luminescence was also observed in the cavitation together with electrostatic charge. All the findings, which cannot be consistently explained by the nucleus theory, lead to the following speculation ; at the separation point a tensile force rips off a liquid particle from the wall, leaving behind a tiny vacuum vecancy, which forms the incipient cavity on the edge. This rip off action also results in electrostatic charges, which cause light emission when discharged in the vacuum.
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  • Katuine TABEI, Hiroyuki SHIRAI, Junichi MOTOJIMA
    1999 Volume 65 Issue 633 Pages 1652-1657
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    The behavior of a single xenon bubble in an adiabatic compression process was investigated theoretically. Rayleigh's equation for the bubble dynamics was coupled with the detailed collisional and radiative processes for xenon plasma to obtain plasma conditions in a bubble. A two-temperature model for electrons and heavy particles was adopted to estimate the luminescence property from a spherical bubble. For the conditions of initial bubble radius of 10 to 150 μm and pressure change of 200 to 800 kPa, the maximum electron temperature ranged from 5000 to 15000 K and electron number densities about 1017 to 1020 cm-3 at the minimum bubble radius. The plasma in a bubble was in thermally nonequilibrium state during the compression process, and generally the maximum electron temperature was significantly lower than the heavy particle one. The emission intensity from cavitation bubbles was sensitive to the change rate of pressure and the bubble radius.
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  • Yoshinori MATSUURA, Hidetaka TANIBAYASHI
    1999 Volume 65 Issue 633 Pages 1658-1664
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Cavitation is principally considered to occur when the pressure is reduced to a certain critical value and is maintained for a certain duration. The present study is therefore intended to investigate an extreme case of maintaining the low pressure for sufficiently long duration. To do this, the pressure in a sealed water container is gradually lowered so as to produce cavitation. The air content and the temperature of the water are systematically varied. The results of the investigation can be summarized as follows. (1) The pressure at the cavitation inception is nearly equal to or less than the published data of vapor pressure of water, and decreases with the air content in water. (2) The superheat increases with decreasing water temperature, and the difference between the vapor pressure and the inception pressure increases with the temperature.
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  • Hideo KASHIMURA, Toshiaki SETOGUCHI, Heuy Dong KIM, Yong-Hum KWEON, Ka ...
    1999 Volume 65 Issue 633 Pages 1665-1670
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    When a shock wave propagates along a constant-area straight tube and reaches open end, an impulsive wave is emitted outward from the tube exit toward the surrounding area. In order to clarify the effects of diameter of a flange at the tube exit, experimental and numerical investigations have been carried out. A simple open-ended shock tube with the flange of the various diameter at the tube exit was used. The magnitude of an impulsive wave, the attenuation with distance and its directivity are discussed with the experimental results. As the results, the effect of the diameter of flange on the magnitude of an impulsive wave was shown. Finally, the effective equations concern with the magnitude of an impulsive wave generated by the emission of a shock wave were obtained from the numerical results solved by the TVD scheme.
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  • Shuji TANAKA, Katsutomo ISONO
    1999 Volume 65 Issue 633 Pages 1671-1679
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Coherent flow fields around a two-dimensional flat plate aerofoil emitting discrete frequency noise in a uniform flow have been determined using phase-locked averaging technique, from which the generation mechanism of the noise has been discussed. The frequency and the noise level were artificially modified using a small circular cylinder inserted in the near wake region. The organized flow details such as velocity fluctuations in the boundary layer, pressure fluctuations on the aerofoil surface as well as the detailed structures of the shedding vortices in the turbulent wake have been presented. The generation mechanism of the discrete frequency noise has been examined in relation to the organized structures in the turbulent wake. It is confirmed that the source of the discrete frequency noise is generated by the organized fluctuating pressures on the aerofoil due to the fluctuating velocities induced by the organized turbulent shedding vortices in the wake.
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  • Kuniyasu OGAWA, Takeshi MATSUKA, Shuichiro HIRAI, Ken OKAZAKI
    1999 Volume 65 Issue 633 Pages 1680-1687
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    For understanding of heat and mass transport in porous system, it is necessary to observe the pore geometries and to measure the local velocity profiles in the interstitial regions at the microscopic scale. Using magnetic resonance imaging (MRI) which has the advantage of noninvasive and nonoptical measurement, analysis of pore structure and velocity measurement of interstitial flow through water-saturated porous media have been performed experimentally. Twe samples consisted of crashed glass particles and spherical beads in the typical diameter range of 2 to 5 mm were used as porous media. Three-dimensional pore images of the porous media were reconstructed from obtained multi-slice images of water saturated porous medium. And then porosity and pore size distributions as pore structure parameters were determined by image analysis based on the images Using spin-echo sequence with tagging pulses for flow visualization, three-dimensional velocity vectors of steady-state flow in the interstitial regions at the pore scale have been measured. The effect of mean flow velocity through the porous medium, which is calculated from flow rate, section area and the mean porosity of the porous medium, on the flow structure has been investigated in range of the mean flow velocity from 3.84 mm/s to 13.2 mm/s. The obtained vector maps show nonuniform flow depending on mean flow velocity and the reversed flow generated due to the pore geometry and the network structure. The frequency distributions of the flow velocities analyzed by statistical treatment spread widely and are influenced sensitively by the pore geometry in the porous media.
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  • Takeharu ETOH, Kohsei TAKEHARA, Koji OKAMOTO
    1999 Volume 65 Issue 633 Pages 1688-1695
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    The PMC method, the particle mask correlation method, was presented to pick up particle images. The KC method, a combinative use of Kalman's filtering theory and the Chi-square test, was developed for particle tracking velocimetry. A set standard particle images in fluid velocity fields were generated to evaluate performance of PTV algorithms. The PMC and the KC methods are applied to the standard particle images, which proved higher performance of these methods than other existing PTV algorithms with respect to resolution of resulting velocity fields.
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  • Yukimaru SHIMIZU, Yasunari KAMADA, Ikuo TOBINAGA
    1999 Volume 65 Issue 633 Pages 1696-1702
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    This paper describes the development of passive system to control the output of horizontal axis wind turbine with teeter and feather mechanism of the blade. When the power generation system with variable speed is applied to the horizontal axis wind turbine, the rotaion speed of rotor increases with the wind speed. This mechanism can suppress the excessive input power in case of excessive wind speed more than the rated wind speed. This mechanism has two kinds of blade motions which are the teetering and the feathering motions. Both motions are coupled together by the special parts. When the blade is teetered downstream, the pitch angle of the blade (feathering angle) is changed to increase the attack angle. Also, these two kind of motions are supported by the spring and the damper which are attached to the mechanism. In this paper the relationships between the ratio of teetering and feathering angles and the braking effect of wind turbine are investigated experimentally. As the result, it is found that the braking effect for rotor is more excellent when the ratio of feathering and teetering is large. Also, the flow pattern around wind turbine is measured by LDV with two dimensions and visualized by tuft grid method and fog method using Laser sheet. It is found that the suppress phenomena of excessive rotation speed is caused by a couple of ring vortices, which are appeared on the area of blade tip side.
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  • Hitoshi NISHIDA, Kunio SHIMADA, Makio IWABUCHI, Toyohisa FUJITA, Kenic ...
    1999 Volume 65 Issue 633 Pages 1703-1709
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    The purpose of this paper is to establish the theoretical prediction that the steady torque characteristics of a rotating disk in ERF can be quantitatively and qualitatively explained. At the first step on the basis of this purpose, the ER effects of electric field and shear rate were investigated by comparison of experimental results of the flow curves between the rotating concentric cylinder type device and the rotating disk one. We clarified experimentally the difference of these flow curves influenced by the electrode gaps.
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  • Hironori SAITOH, Sadanari MOCHIZUKI, Akira MURATA, Hiroshi SAITOH
    1999 Volume 65 Issue 633 Pages 1710-1715
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    One of the promising trends to increase the thermal efficiency of gas turbines is to raise the gas temperature at the turbine inlet. In modern gas turbines, turbine section operates under severe thermal conditions. Cooling of the turbine section is one of the key technologies for further improvement of gas turbines to keep their safe working. The objective of this study is to investigate the flow and heat transfer in a low-pressure turbine which has cavities formed by an assembly of turbine disks. This study employs two dimensionless parameters which govern flow and heat transfer in rotating cavities. These are throughflow Reynolds number and rotational Reynolds number. Flow visualization and heat transfer experiments in rotating situation were carried out in wide range of experimental conditions. This paper focuses on the effect of forced convection by the throughflow on flow and heat transfer characteristics in rotating cavities.
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  • Takayuki TSUTSUI, Tamotsu IGARASHI, Hajime NAKAMURA
    1999 Volume 65 Issue 633 Pages 1716-1723
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Fuel oil storage tanks are set up all parts of the world for stable energy supply. In a cold district, the oil must be keeping warm. In the plane of the heating system of the tank, it is necessary to estimate the heat loss from the shell and roof of the tank. To make the basic data, experimental studies were carried out on the fluid flow and local heat transfer around a cylindrical protuberance with the height/diameter ratio of 0.35 mounted in a flat plate laminar and turbulent boundary layer. The local drag coefficient and characteristics of the local and average heat transfer around the cylinder are clarified. The results obtained were compared with the ordinary results of a cylinder with the height/diameter ratio of 1.0.
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  • Yoshihiro KIKUCHI, Hiroshi SUZUKI, Masanori KITAGAWA, Ken-ichiro IKEYA
    1999 Volume 65 Issue 633 Pages 1724-1730
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    An experimental study was conducted to investigate the effect of pulsating Strouhal number, Sγp, on flow and heat transfer around a heated cylinder in a pulsating cross-flow. Averaged Reynolds number was kept at 400 while oscillatory Reynolds number was changed from 40 to 300. Pulsating Strouhal number, Sγp, ranged from 0 to 1.37. Two remarkable peaks of the mean Nusselt number were observed at approximately Sγp=0.2 and 0.6. Flow visualization experiments revealed that twin symmetric vorticies were periodically formed behind the cylinder at Sγp corresponding to the 'lock-on' of the shedding of vortices. From results of velocity field measured by PIV, it was found that the flow reversal approaching to the back face of the cylinder was intensified by twin vortices. This flow reversal caused heat transfer enhancement on the back face of the cylinder.
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  • Ryo KUBO, Satoshi KUMAGAI, Noritsugu UMEHARA
    1999 Volume 65 Issue 633 Pages 1731-1736
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Microbubble emission boiling (MEB) is the phenomenon that shows emission of micro bubbles from a heat transfer surface in a wall temperature region corresponding to transition boiling. Since MEB performs higher heat flux than critical heat flux of nucleate boiling, application to engineering field is expected. However, MEB has unknown characters such that it sometimes results in serious erosion on the surface. Scanning electron microscope observation on the heat transfer surface after MEB occurred, shows that the surface erosion is consisted of numerous craters. This result leads to a hypothesis that the mechanism of MEB includes bubble collapse process caused by liquid micro jets. Surface roughness was measured in various heat flux conditions and the relation of it with heat transfer was considered. The results made it clear that there is a critical heat flux to cause surface erosion. This heat flux is also the transition point of bubble collapse regimes in MEB, from heat transfer dominant to inertia controlling.
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  • Osamu AKAIKE, Toshihiro TSUJI, Yasutaka NAGANO
    1999 Volume 65 Issue 633 Pages 1737-1742
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    Numerical simulation of tubular blown film processing of plastics provides a tool for air ring designs and suitable polymer properties. Although cooling air plays a key role in the process ability and film properties, there have been few research works taking account of the cooling air effect correctly. We have performed a numerical analysis of cooling air flow and heat transfer from the surface of molten polymer using turbulence models, and then we have simulated a tubular blown film process under the thermal boundary conditions estimated from the numerical analysis. The film bubble shape predicted has coincided well with experimental data.
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  • Akiyoshi OHIRA, Michio YANADORI, Kunihiko IWABUCHI, Toshikatsu KIMURA, ...
    1999 Volume 65 Issue 633 Pages 1743-1751
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    This paper deals with cold energy release characteristics of an ice/air direct contact heat exchanger. Characteristics of the outlet temperature, humidity, time history of heat release are examined when the initial height of the ice-cube-packed bed in the heat exchanger is changed. The following results are obtained in these experiments : (1) Inlet air of 30°C is lowered to about 0°C when passed through the heat exchanger, and the absolute humidity of the outlet air is reduced to about a quarter of that of the inlet air. (2) There is an optimum height of the ice-cube-packed bed to maximize the amount of cold energy release. (3) This heat exchange method can supply about twice as much cold energy as is released by an ordinary fin-tube-type heat exchanger even if the air velocity in the heat exchanger is reduced to about 0.38 times that of the fin-tube-type heat exchanger. (4) An experimental equation for predicting the time taken for the ice-cube-packed bed to completely melt is derived.
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  • Shoji TAKADA, Kunihiko SUZUKI, Yoshiyuki INAGAKI, Yukio SUDO
    1999 Volume 65 Issue 633 Pages 1752-1758
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    An experiment was performed to simulate an air cooling panel system for passive decay heat removal from a high-temperature gas-cooled reactor to investigate the performance of decay heat removal and the temperature distributions of components of the system. The experimental apparatus consisted of a pressure vessel 1 m in diameter and 3 m in height, bristling with nineteen simulated stand pipes atop and containing heaters with the maximum heating rate of 100 kW which simulated residual heat of the core, and cooling panels surrounding the pressure vessel. The analytical code THANPACST2 was applied to the experimental data to investigate the validity of the analytical method and model proposed. Under the conditions of helium gas at the pressure of 0.64 MPa and temperature of 514°C in the pressure vessel, the temperature distribution of the pressure vessel was properly estimated within differences of -10 to +50°C compared to the experimental data. The analysis indicated that the heat transferred to the cooling panel was 15.4% less than the experimental value.
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  • Shhin-ichi SATAKE, Tomoaki KUNUGI, Akira SHIMADA
    1999 Volume 65 Issue 633 Pages 1759-1766
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A direct numerical simulations (DNS) of the fully developed axially rotating turbulent pipe flow was carried out. The Reynolds number, which is based on bulk velocity Ub and pipe diameter D, was set to be 5 286, while rotating rates N=uφ|ω/Ub were 0.25, 0.30 and 0.35. The Statistics obtained were the mean flow, the root-mean-square value of the fluctuating velocities, and the anisotropy invariant. It was found that the friction coefficient decreased with the rotation rate increase. Detailed distribution of the turbulent kinetic energy and Reynolds stress budgets are also presented.
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  • Shin-ichi SATAKE, Tomoaki KUNUGI, Akira SHIMADA
    1999 Volume 65 Issue 633 Pages 1767-1772
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A direct numerical simulation (DNS) with turbulent transport of a scalar quantity was performed for fully-developed turbulent rotating pipe flows. In this paper, the Reynolds number, which is based on bulk velocity and pipe diameter, was constant ; Reb=5293, and the rotation ratio of a wall velocity to a bulk velocity were set to be 0.25, 0.3 and 0.35. A uniform heat-flux was applied to the wall as a thermal boundary condition. Prandtl number of the working fluid was 0.71. The turbulent statistics such as the mean temperature, temperature fluctuations, and scalar flux distribution were obtained. The turbulent heat transfer decreases with the rotating ratio increase. Moreover, the scalar-flux budgets were also obtained for each rotation ratio.
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  • Satoshi HIRANO
    1999 Volume 65 Issue 633 Pages 1773-1778
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Behavior of space cooling system using the diurnal range of atmospheric temperature in the summer is characterized by numerical simulation. The system consists of radiators, a thermal energy storage tank, fan-coil coolers, and an electric cooler. Conditions for the calculation are assumed from the actual weather and characteristics of appliances. Total consumption of electric power is used for evaluating the system performance. The larger the volume of the storage tank becomes, the smaller the consumption becomes. The consumption is smaller in case the radiator is operated for a period of some limited hours than in case through the night. To decrease the consumption, there are also the most suitable values in the flow rate of the pumps and in the on off temperature of the fan-coil cooler. Stratified tanks could reduce the consumption by 3.3% compared with mixed ones. This system has a possibility to reduce demand for electricity or shift the demand to off-peak hours.
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  • Masaharu KOMIYAMA, Akira MIYAFUJI, Toshimi TAKAGI
    1999 Volume 65 Issue 633 Pages 1779-1785
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Instantaneous and simultaneous measurements of two-dimensional temperature, velocity and OH concentration profiles by combining Rayleigh scattering image velocimetry (RIV) with OH laser induced fluorescence method (OH-LIF) were demonstrated in a turbulent nitrogen-diluted hydrogen (H2 30%+N2 70%) diffusion flame. This measuring technique mainly employed one double-pulsed Nd : YAG laser, one Nd : YAG pumped dye laser, and three image-intensified CCD cameras. OH concentration was measured quantitatively based on OH-LIF intensity and the calibration considering the OH-LIF quenching database. The strain rate along the flame surface (reaction zone of OH peak) was estimated by the velocity vectors and OH concentration profiles. The results obtained are as follows. (1) Local temperature and OH concentration depression in the flame tends to occur when the flame inclines toward the centerline and the strain rate becomes positive and high. On the other hand, the flame that has locally high temperature and OH concentration tends not to have positive and high strain rate. (2) When the flame surface is pushed outward by the lateral convection motion, the radial position of OH concentration peak tends to be located prominently outside of the temperature peak. Their profiles are much different from those of the laminar flame. The considerably high OH concentration as compared with the laminar flame was observed where the flame does not have positive and high strain rate.
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  • Hiroyuki SATO, Kenji AMAGAI, Masataka ARAI
    1999 Volume 65 Issue 633 Pages 1786-1792
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    Flame lengths of gas jet diffusion flames were measured under various gravity evels. A spin tester was used to obtain a high gravity field which level was changed from normal gravity (G=1) to G-20. In order to investigate the fuel density effect on flame structure at high gravity level, two kinds of fuels (methane and propanw) and further methane-propane mixture fuel whose density was equivalent to the surrounding air were used. As the results, flame length decreased with an increase of gravity level regardless of the positive and negative buoyancy effect between the fuel and surroundings. To investigate the gravity effect on flame structure, length of blue flame which appeared at anchor portion of the flame was measured under various gravity levels. It was confirmed that the blue flame was expanded with an increase of the gravity level. This result was explained by the enhancement of the air entrainment at the anchor portion of the flame. Evaluation of flame length which was obtained by Altenkirch considering the relationship of fuel and required oxygen were used to evaluate the experimental data of flame length under the various gravity level. From this method the following empirical correlation was proposed : Lfo=1.72Re0.6670.0846, where Lf is a flame length, γo is a nozzle radius, Re is the Reynolds number based on nozzle radius and Fγ is the Froude number.
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  • Kazuhiro HAYASHIDA, Kenji AMAGAI, Masataka ARAI
    1999 Volume 65 Issue 633 Pages 1793-1799
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    Laser induced fluorescence was applied for the measurement of OH concentration in the propane diffusion flames. A tunable, narrow band KrF excimer laser was used to excite the A(ν'=3)←X(ν"=0) band of OH radical. An emission spectrum of the induced light from the flames was measured by a spectroscope. An OH fluorescence component was picked up from the emission spectrum in order to obtain the accurate distribution of OH fluorescence in the flames. We call this method for spectrum-LIF (S-LIF). The spectrum of the induced light from the diffusion flames was compared with that of the premixed flames. Although the spectrum had only OH fluorescence components in the case of premixed flames, high intensity emission from the yellow flame appeared on the LlF image in the case of diffusion flames. To remove the high intensity emission from the LIF image, off resonance image was deducted from the OH resonance image as the background image. Using this deduction method, a planer laser induced fluorescence (P-LIF) was tried to measure the distribution of OH fluorescence. OH fluorescence distribution measured by P-LIF was compared with that of S-LIF. As the result, the P-LIF image qualitatively agreed with the data of S-LIF.
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  • Kunihiko NAMBA, Kyoji KIMOTO
    1999 Volume 65 Issue 633 Pages 1800-1806
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    The ignition and combustion behavior of single droplets of asphalt/water emulsified fuel (As/W) were observed in an electric furnace in order to obtain fundamental data for practical use. The ignition delay and the burnout time of single droplets of asphalt. C-heavy oil and As/W emulsions were investigated under specified furnace temperatures. Each fuel showed peculiar ignition and combustion behavior, and especially As/W emulsified fuel-J (As/W J) had a very strong microexplosion. The values of the ignition delay and the burnout time of As/W emulsified fuels were smaller than those of asphalt and C heavy oil. The reason can be explained by the occurrence of the microexplosion phenomena. Thus, the mechanism was discussed for some factors related to the phenomena.
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  • Shunsuke KITO, Kazunori WAKAI, Shuhei TAKAHASHI, Naohiro FUKAYA, Katsu ...
    1999 Volume 65 Issue 633 Pages 1807-1812
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    A hydrogen jet ignition method is proposed to control the combustion of lean mixtures. The hydrogen jet is supplied from the cavity whose volume is less than one percent of main chamber volume through a nozzle. The heat flux at the wall in the main chamber and the NOx emission are measured. It is shown that the heat flux becomes smaller as the combustion duration is longer. On the contrary, the heat flux of hydrogen jet ignition is smaller than that of conventional ignition when the combustion durations are equal. The NOx emission of hydrogen jet ignition is bigger than conventional ignition when the equivalence ratios are the same. The NOx emission of very lean mixture whose combustion duration is reduced less than that of conventional ignition of stoichiometric one is smaller than that of conventional ignition of it. It is shown that the NOx emission is reduced keeping the fast combustion duration by using hydrogen jet ignition method.
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  • Takeshi SAITO, Yuji IKEDA, Shigeo HOSOKAWA, Tsuyoshi NAKAJIMA, Yoji KU ...
    1999 Volume 65 Issue 633 Pages 1813-1821
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    The mixing characteristics and flame holding mechanism inside a model ram combustor was experimentally investigated by using a Fiber Laser Doppler Velocimeter (FLDV) under non-reacting and reacting conditions down-stream of the bluff body type flame holder. The FLDV was optimized regarding the high flow speed and combustion. The evaluation of the FLDV measurement system and a new data analysis method, called Slot-Correlation, were applied. The results of the reacting experiment presented a striking contrast to that of the non-reacting flow. The jet penetration and the reverse flow regions were found to have three-dimensional structures. The Slot-Correlation method was applied to evaluate the turbulent structure around the strong shear layer behind the bluff body. Distribution of integral scales inside the shear layer and oscillations at the end of the recirculation zone were captured.
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  • Murari Mohon Roy, Hideyuki Tsunemoto, Hiromi Ishitani
    1999 Volume 65 Issue 633 Pages 1822-1828
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    Concerns about exhaust odor from DI diesel engines have increased in recent years. In this paer, sensual assessment for the odor and eye irritation of exhaust gases directly from engine exhaust and indirectly from sampling bags were performed. The HCHO in the exhaust was measured and found that it correlates with odor and eye irritation well. For the reduction of odorous emissions, the effects of injection timing, rate of EGR and engine speed on emissions were investigated. The injection timing of about 10°BTDC shows good results after and during engine warm-up. The effects of EGR on odorous emissions were also examined. The investigation shows that 30% EGR is the optimum rate of EGR for minimum odor and eye irritation. At higher engine speeds, the speed of assessed gas increases which may cause the deterioration of sensual assessment in the outdoor.
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  • Naoya ISHIKAWA, Long ZHANG
    1999 Volume 65 Issue 633 Pages 1829-1837
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
    JOURNAL FREE ACCESS
    The behavior of air-entrainment into a diesel fuel spray was studied by analyzing the air movement around a free non-evaporating diesel spray in a pressurized vessel. To measure the air movement around the spray, a density difference in the air was made near the surface of the spray as a tracer by heating a SUS wire with large current and the movement of air induced by the spray can be visualized through this density difference. The effects of nozzle hole, injection velocity and ambient air density on the air-entrainment behavior were investigated by this method. The air-entrainment relating to air-fuel ratio and the time dependent change of local air-entrainment were shown. These results indicated that using smaller nozzle hole and increasing ambient air density can increase the air-entrainment into the spray but increasing the injection velocity has little effect on the air-entrainment. Meanwhile, the results of this study were compared with the existing momentum theory, and the possibility of using momentum theory to predict the air-entrainment was described in the paper. Based on comparing the averaged air-fuel ratio inside the spray with both values of measurement and predicted by momentum theory, some discussions were added to help considering the complex phenomena of air-entrainment into a unsteady diesel spray.
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  • Kazushige KIKUTA, Ryo YUYAMA, Takemi CHIKAHISA, Yukio HISHINUMA
    1999 Volume 65 Issue 633 Pages 1838-1844
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    This paper investigates the simulation characteristics of diesel sprays with DDM (Discrete Droplet Model), which is commonly used in engine combustion simulations. In this study KIVA-II code, which was developed in Los Alamos National Laboratory in the United States and it is one of the most popular simulation programs for diesel combustion, was used for the analysis. With making the evaporation speed and the droplet diameter agree with experiments, the penetration of fuel vapor was investigated, as it is closely related to the air-entrainment in the fuel spray. Comparisons were made for mesh sizes, turbulence factors, and drag coefficient of the droplets. The results show that the non evaporating spray can be simulated well by adjusting the parameters, but the evaporating spray is hardly simulated well by the adjustment. It strongly depends on mesh sizes and almost infinitesimal mesh is required particularly at the vicinity of the nozzle exit. A method to have good simulation results for the evaporating sprays with the coarse mesh is demonstrated in the paper, but further investigation is necessary for the appropriate simulation of combusting sprays.
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  • Masatake YOSHIDA, Kensuke TOMINAGA, Takashi SUZUKI, Yasufumi OGURI
    1999 Volume 65 Issue 633 Pages 1845-1850
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    Although numerous reports show that the amount of new-charged air taken into a gasoline engine is greatly influenced by heat transfer in intake system and during intake process, identifying the actual heat transfer process in an intake system is extremely complex due to unsteady flow of new -charged air. Based on thermodynamics model, an equation which estimates the temperature of new -charged air before entering combustion cylinder was derived. The experiment using a modeled intake port was conducted under the following ranges : mass flow rate=0.5∼10 g/sec and wall temperature of intake port=323∼383K. In addition, motoring test was conducted under the similar ranges. The results were compared with the temperature of new-charged air obtained from the equation. They can be fit within about ±2.0 K and ±6.0 K under the steady flow model and motoring test respectively.
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  • Michihiro OHTOMO, Naotsugu ISSHIKI
    1999 Volume 65 Issue 633 Pages 1851-1855
    Published: May 25, 1999
    Released on J-STAGE: March 28, 2008
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    A new general three-temperature three-cylinder Stirling cycle machine designed by vector analysis reported before has been manufactured and experimented. The machine has three cylinders (Hot, Middle and Cold temperature) and the phase angle of the Hot piston can be changed between 80 and 160 degrees to the Middle piston. The measured performance and the P-V diagrams of each cylinder in various experiments are shown to agree well with the predicted values by vector analysis. Also, the change of performance of each cylinder by Hot piston phase change is qualitatively similar to the theoretical one. Moreover, applications of this kind of machine are reported.
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