JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 42 , Issue 2
Showing 1-21 articles out of 21 articles from the selected issue
  • Marcel LESIEUR
    1999 Volume 42 Issue 2 Pages 143-153
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    We present a point of view of large-eddy simulations(LES)in Fourier space, where the eddy coefficients are expressed thanks to a two-point spectral closure of isotropic turbulence, the EDQNM theory. Returning to real space, this leads to models of the structure-function family(plain, selective or filtered). These models are applied with success to predict the statistical distributions and coherent-vortex dynamics for a wide variety of turbulent flows. In three-dimensional decaying isotropic turbulence, we confirm the existence of a κ4 infrared backscatter in the kinetic-energy spectrum, and predict a new κ2 law for the pressure spectrum in this range. In the mixing layer(temporal or spatial), we show how to manipulate the topology of Kelvin-Helmholtz vortices, from quasi two-dimensionality to helical pairing. The latter vortex organization is found in a backward-facing step just behind the step, and yields big staggered Λ-vortices which are carried away downstream. In a developed turbulent boundary layer, coherent vortices are hairpins generated above the low-speed streaks by a secondary Kelvin-Helmholtz instability. Afterwards, we consider LES of compressible turbulence, studied with Favre averages, and where the introduction of a macro-temperature and a macro-pressure simplifies greatly the problem. Finally, we show in rotating shear flows(free or wall bounded, axis of rotation in the spanwise direction)a universal behaviour of the mean velocity which becomes linear in certain anticyclonic regions.
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  • Masayoshi OKAMOTO, Nobuyuki SHIMA
    1999 Volume 42 Issue 2 Pages 154-161
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The model expression for the subgrid-scale(SGS)Reynolds stress and the transport equation of the SGS energy are theoretically derived using a two-scale direct-interaction approximation(TSDIA). Applying the model to three-type flows, i.e.a homogeneous decaying turbulence, a mixing layer and a channel flow, the model constants are optimized and the results are compared with those of the Smagorinsky model in detail. Consequently, it is found that this one-equation model has two deficiencies. One is that the model-constants are dependent on flow fields like the Smagorinsky model. The other is that an exact asymptotic-behavior of the SGS energy in the vicinity of the wall is not satisfied by this one-equation model. Therefore, for the purpose of improving the near-wall profiles for the SGS quantities in this model, a new model for the SGS dissipation rate is suggested on the basis of a low-Reynolds-nomber Κ-ε model. Moreover, using the model including a high-order term of the SGS Reynolds stress, a new one-equation model which is applicable to several flows with fixed model-constants is proposed.
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  • Koichi TSUJIMOTO, Yutaka MIYAKE, Takeshi YOSHIKAWA, Takeshi MORIKAWA
    1999 Volume 42 Issue 2 Pages 162-170
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Our aim is concerned with clustering or grouping of quasi-streamwise vortices. A fact that quasi-streamwise vortices are not distributed homogeneously but intermittently populated in space in a wall layer, is shown at first by referring to a Direct Numerical Simulation(DNS)data for a channel flow. Then, Regeneration property of quasi-streamwise vortices is one of the crucially important possible mechanisms for this clustering is shown by a simplified non-dynamical simulation. Next, a wavelet decomposition of quasi-streamwise vortices in two scale-based groups is shown. The interaction between vortices of two groups indicates that individual quasi-streamwise vortices can not survive long without assistance of surrounding large scale structure which is adapted for them. Thus, it is pointed out that large scale structure around a cluster of vortices is an important coherent ctructure to be investigated more in detail.
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  • Hideki TAKAGI, Yukimaru SHIMIZU, Norihisa KODAN
    1999 Volume 42 Issue 2 Pages 171-177
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The purpose of this study is to measure active drag, which is dynamic drag acting on a self-propelling swimmer in water. We developed a new measurement device, which was capable of measuring active drag without disturbing natural swimming in a circulating water channel. Four collegiate skilled swimmers volunteered to participate in this study. The subjects were asked to swim front crawl and to keep the pre-determined stroke frequency within a range of 0 m / s to 1.8 m / s flow velocity. The active drag was estimated by means of the relationship between residual thrust(thrust minus the resistance)and passive drag(static drag acting on a prone position swimmer). As a result of these development, it was possible to measure active drag more precisely than before, and to obtain the experimental equation that predicted the active drag within a range of Reynolds number equaled the actual swimming velocity.
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  • Shuji TANAKA, Susumu MURATA
    1999 Volume 42 Issue 2 Pages 178-187
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Time-averaged flow fields behind finite circular cylinders with aspect ratios from 1.25 to 10 placed on a ground plate in a uniform flow were determined at a Reynolds number of 3.7×104 and influences of the aspect ratios on the wake structures have been presented. Three-dimensional velocity distributions from 1 to 20 diameters down-stream of the cylinders were measured using newly developed rotating yaw-meter system, from which the details of the wake flow fields behind the finite circular cylinders have been discussed. Streamlines and vortex lines were calculated from the velocity fields and the wake structures, such as the configurations of vortices in the wake and their changes in shapes with distance downstream, have been shown. Effects of the shapes of the cylinder top on the wake flows have been also examined using modified cylinders with a hemispherical fairing, circular pipes as well as flat plates.
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  • Shinji NAKAGAWA, Mamoru SENDA, Atsushi HIRAIDE, Shinzo KIKKAWA
    1999 Volume 42 Issue 2 Pages 188-196
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    An experimental study of heat transfer has been conducted in a channel flow with a rectangular cylinder having various width-to-hight ratios, b / h, of 0.5, 1, 2 and 3. Time-averaged heat transfer coefficients and the fluctuations of wall heat flux have been measured. Heat transfer is augmented extensively at the downstream region of the cylinder. In order to examine the relationship between the heat transfer enhancement and the shedding vortices from the cylinder, flow visualization by a smoke-wire method using a high-speed video recording system has been carried out simultaneously with wall heat flux measurement. It is clarified that the heat transfer is augmented by the wall-ward flow induced by the clockwise and counterclockwise vortices shed alternately from the cylinder.
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  • Hiroshi ISHIGAKI
    1999 Volume 42 Issue 2 Pages 197-205
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    This paper describes a quantitative analogy between developing laminar flows in the inlet regions of curved pipes and orthogonally rotating straight pipes through similarity arguments and computational studies. Three-dimensional developments of these flows are characterized by secondary flows due to the centrifugal or the Coriolis force. Similarity considerations with taking the secondary flow into account result in a pair of governing parameters and a dimensionless axial distance for each flow. When the second parameter is large enough in each flow, we have a quantitative analogy between them ; the computed results for the two flows show strong similarity regarding the developments of flow structure, wall friction, and velocity profile of primary and secondary flows.
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  • M.K. ALKAM, M.A. AL-NIMR
    1999 Volume 42 Issue 2 Pages 206-213
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this work exact solutions for different classical fluid flow problems in porous domains are presented. These problems include the transient Couette flow, Stokes' first and second problems in semi-infinite porous medium, pulsating flow in porous channels, steady flow in convergent and divergent porous channels, transient flow in porous annuli confined between two rotating cylinders and upward moving liquid film in porous domain.
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  • Tatsuro WAKIMOTO, Tsuneo AZUMA
    1999 Volume 42 Issue 2 Pages 214-223
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In this paper, the mechanisms of breakup and frop formation of a radially thinning liquid sheet, which are attributed directly to the transition from laminar to turbulent flow, are described. A radial liquid film flow is generated by water discharge from one end of a cylindrical nozzle through a small gap present between the end of the nozzle and the flat surface of a disk. The liquid film spreads radially outward on the disk as a sheet, slowing from the edge of the disk into the air. Sudden laminar-turbulent transition occurs in the liquid sheet when the Reynolds number exceeds a critical value, resulting in both perforation and disintegration of the sheet under an extremely high Reynolds number. The breakup process through perforation, ligament formation and drop formation is observed both by zoom-in photography using a single pulse strobe and a steel camera and high-speed photography using a multipulse laser and a drum streak camera. These photographs clearly show that droplets a few tens of micrometers in size are produced from the liquid sheet. Flow conditions for the occurrence of atomization induced by the transition are also presented.
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  • Jeong Heon KIM, Tsuyoshi NAKAJIMA
    1999 Volume 42 Issue 2 Pages 224-229
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    To investigate aerodynamic influences on liquid atomization in an electrostatic spray, the diameter, velocity and velocity-size correlation characteristics of droplets were simultaneously measured using phase Doppler techniques. The processes associated with the break-up of charged jets were also observed using laser sheet flow visualization. Experiments were carried out using heptane, which was doped with an antistatic additive to enhance its electrical conductivity to that of a semiconductor. The electrostatic atomization of the liquid depended primarily on the charging voltage, and the droplet size distribution was characterized by two peaks. Aerodynamic influences on the atomization of the liquid in electrostatic sprays decreased with charging voltage. The velocity-size correlation of droplets reflected the atomization mechanism.
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  • Norihiro YAMAMURA, Kazuo MATSUUCHI, Masahiko ONDA, Shinobu YAMAZAKI, A ...
    1999 Volume 42 Issue 2 Pages 230-237
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The aerodynamic characteristics of station-keeping airships at high Reynolds numbers were examined. The boundary layer flow developed on the hull surface was sucked in by an axial flow fan through a slot located at the rear part of the airship and the sucked-in gas was blown out as a jet. Two models, one with and one without a cusp attached to the inlet of the suction slot, were designed to validate the effects of the cusp. The flow field near the inlet, in particular the pressure on the hull surface, was measured by varying the suction flow rate. We obtained the form drag data by integrating the pressure distribution in a wide range of Reynolds numbers and of suction flow rates. Taking into account the jet thrust and the calculated friction drag, we determined the total drag and evaluated the role of the cusp. It has been found that the effects of the cusp are significant and responsible for reducing the drag.
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  • T.L. YANG, S.W. CHANG, L.M. SU, C.C. HWANG
    1999 Volume 42 Issue 2 Pages 238-248
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    This paper describes a detailed experimental investigation of heat transfer for confined impinging jet onto spherically concave surface with piston cooling application. The experimental conditions involved several nominal Reynolds numbers renging from 17 500 to 43 200 with five different reciprocating frequencies, namely 0, 0.833, 1.25, 1.67 and 2.08 Hz. It resulted in the pulsating number, which represented the ratio of reciprocating force to inertial force effect, varying from 0 to 1.85E-4. Along the spherically concave heating surface the evolution of flow structure from separation point into laminar and then turbulent annular flows was demonstrated by examining the variations of power index suffixed to Reynolds number in the non-reciprocating Nusselt number correlations. The typical effects of flow reciprocation on heat transfer were then illustrated by examining the distributions of temporal Nusselt number variation along the heating surface. When test section reciprocated, the Nusselt numbers at measurement locations periodically oscillated and the amplitude of such temporal Nusselt number variation was mostly pronounced at the stagnation point and became location and Reynolds number dependent. At the stagnation point, there were coupling effects of Reynolds and pulsating numbers on heat transfer and, in general, the heat transfer level increased with the increase of Reynolds or pulsating numbers while kept one of these two flow parameters unchanged. At Reynolds and pulsating numbers of 40 000 and 8.41E-5, the reciprocating Nusselt number value at the stagnation point could be increased up to a level about 3.2 times of the non-reciprocating level. Less reciprocating effects were found in the spherically concave heating area ; and reciprocation reduced the time-averaged heat transfer to the levels abut 80%-95% of non-reciprocating heat transfer values after flow passed the concave surface. As the reciprocating force significantly modified the heat transfer from non-reciprocating situation, it needed to account for the effect of reciprocating motion on the heat transfer within the coolant channels of piston in order to achieve the optimum design of cooling system.
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  • Seizo KATO, Hangxiang HU
    1999 Volume 42 Issue 2 Pages 249-254
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    By using the molecular dynamics method(MD)and computer graphics(CG), the surface processing mechanism of SiH2→Si+2H in LP-CVD silicon wafer fabrication is analyzed, in which we introduce a chemical reaction model consisting of the activating energy and attack angle between SiH2 gaseous molecules and Si atom monocrystalline. The atom surface adsorption and inelastic collision are discussed considering energy exchange between the particles and surface. Moreover, the potential state and behavior of hydrogen atom adsorbed as a free particle are also calculated and discussed. The relevant potential surface of H free particle in the Si crystal lattice is found to be useful to understand its potential state and behavior.
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  • Kunito OKAYAMA, Atsushi OGAWA, Yoshihiro IIDA
    1999 Volume 42 Issue 2 Pages 255-261
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The reaction and heat transfer characteristics of catalyst-coated fins, which are used to circumvent low catalyst loadings in wall-supported catalytic reactors, are investigated theoretically in an attempt to examine the effects of important non-dimensional parameters on fin performance for endothermic reaction cases. The fin efficiency of the reaction rate is found to decrease markedly, more than that of convection heat transfer, with an increase of heat absorption rate by the reaction and / or the convection heat transfer rate, for the case in which the conversion rate is governed by the intrinsic kinetics of the catalyst. The increase of bulk fluid temperature to the fin base temperature increases the fin efficiency of the reaction rate, under chemical kinetics limitation, due to convection heating of the fin while the fin temperature decreases along the structure due to heat absorption. An increase of the effect of convective mass transport on the reaction rate increases the fin efficiency of the reaction rate.
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  • Tatsuya TANAKA, Michihiko TABATA
    1999 Volume 42 Issue 2 Pages 262-267
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Planar Laser-Induced-Fluorescence technique was applied to measure the NO fluorescence distribution in a spark ignition engine. The fluorescence intensity had high value near the flame front, and gradually decreased from the flame front to the postflame gas. The fluorescence was distributed in the broad flame zone as compared with the case of the constant-volume combustion chamber. The effect of equivalence ratio on the NO fluorescence intensity were investigated. At the flame-development duration, the total NO fluorescence intensity was high as the equivalence ratio became rich. However, at the rapid-burning angle, the total NO fluorescence intensity of a slightly lean condition had a maximum value. As the equivalence ratio became lean, the peak intensity of the radial NO fluorescence distribution increased and the width of the high intensity zone in radial distance broadened. The peak intensity and the width of the radial distribution reached the maximum value at a slightly lean condition.
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  • Yuichi GOTO
    1999 Volume 42 Issue 2 Pages 268-274
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A natural gas fueled direct injection test engine, equipped with a newly developed natural gas injector, was designed and the influences of injection timing and spark timing on indicated mean effective pressure and exhaust emissions were investigated. The following results were obtained:(1)The location of the spark plug relative to the injection nozzle location and the piston cavity wall needs to be optimized to achieve a wide range of stable ignition and engine operating conditions;(2)Impingement of the gas jet against the cavity wall and high injection pressure are two key factors required to control ignition and combustion of the gas jet;(3)In terms of mixture preparation around the spark plug, early injection is preferable at low load conditions, and late injection at high load conditions;(4)When excess air ratio λ is 1.06 and 1.4, THC concentration was about 1 000 ppm and NOx concentration exceeds 1 000 ppm. When λ values are 2 and 2.3, THC concentration was high but NOx concentration was below 100 ppm.
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  • Terumi INAGAKI, Yoshizo OKAMOTO
    1999 Volume 42 Issue 2 Pages 275-283
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Infrared thermography is applied to the measurement of turbulent heat transfer in order to investigate its applicability under near-ambient conditions. Natural convection along a vertical smooth flat plate and forced convection along a smooth flat plate are realized in a large darkroom, where individual heat transfer coefficients are quantitatively measured using infrared thermography in the laminar, the transition and the turbulent regions. The measurement error is then estimated using the uncertainty analysis based on ANSI / ASME PTC 19.1-1985 to confirm the accuracy. It is obvious from a series of application experiments and error analyses that the present technique is useful for estimating turbulent heat transfer quantitatively and dynamically. Infrared thermography is an appropriate measurement procedure for engineering applications because it can be applied to diagnose a two-dimensional and dynamical temperature field instantaneously and nondestructively.
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  • Takeshi YANO, Nobuhide KASAGI
    1999 Volume 42 Issue 2 Pages 284-292
    Published: May 15, 1999
    Released: February 18, 2008
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    Turbulent scalar transport phenomena at high Prandtl numbers up to Pr=100 were examined through direct numerical simulations of forced isotropic turbulence with a constant mean temperature gradient. The main storage required for computation was significantly reduced by employing a different number of numerical grids for each of the velocity and temperature fields, which contained markedly different microscales. At high Prandtl numbers, the pressure temperature-gradient correlation was found dominant, instead of the molecular dissipation, as a sink term in the turbulent heat flux budget. It was also found that low-wave-number components of the velocity fluctuation were solely responsible for the cascade of the temperature fluctuation irrespective of the Prandtl number.
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  • Kazunari MOMOSE, Kiyoshi SASOH, Hideo KIMOTO
    1999 Volume 42 Issue 2 Pages 293-299
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A numerical approach based on the adjoint formulation of forced convection heat transfer is proposed, to evaluate the total or mean heat transfer rate under arbitrary thermal boundary conditions. Using the numerical solution of the adjoint problem under the uniform Dirichlet condition, which can be computed by a slightly modified CFD code, an influence function of the local surface temperature can be obtained. As a result, the total heat transfer for arbitrary surface temperature distributions can be calculated by the influence function. In a similar fashion, using the numerical solution of the adjoint problem under the Neumann condition, the mean surface temperature can also be expressed as an influence function of the local heat flux distributions. The influence functions for a circular cylinder and for an in-line square rod array are presented to illustrate the present method.
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  • Yasuo MORI
    1999 Volume 42 Issue 2 Pages 300-309
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In consideration of recent incidents caused by leakage of Na in the LMFBR, studies have been conducted on the indirect He cooled fast breeder reactor with the He turbine power generation system(GT-HeFBR)and freshwater desalination production unit in the secondary loop. Desalination is conducted by use of exhaust heat from He turbine. The plant has the features of high safety, reliability, thermal efficiency and economic competitiveness. Reactor performances are enhanced by use of the long annular type He passage in the reactor in the primary loop. Economic competitiveness is attained by the electricity generation of high efficiency. The He turbine electric power generation of the maximum system efficiency of 44% and the efficient production of freshwater for the local use are performed in the secondary loop. The processes give a total thermal efficiency of about 90%.
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  • Takehiro YAZAKI, Katsumi SUZUKI, Myeong Kwan PARK, Shuzo OSHIMA, Ryuic ...
    1999 Volume 42 Issue 2 Pages 310-317
    Published: May 15, 1999
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Utilization of the electromagnetic force realizes the control of the shape and the flow of the molten metals without contact with the surrounding wall surfaces, leading to improved quality of the products. In the present research the new method to control the direction of the liquid metal jet by means of a series of the skewed non-uniform DC magnetic fields was proposed, and the experimental and the theoretical studies were conducted. The deflection of the jet increases with the increase in the amplitude of the magnetic flux density and with the decrease in the wavelength of the magnetic field and in the effect of the gravity.
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