JSME International Journal Series B Fluids and Thermal Engineering
Online ISSN : 1347-5371
Print ISSN : 1340-8054
ISSN-L : 1340-8054
Volume 38 , Issue 1
Showing 1-21 articles out of 21 articles from the selected issue
  • Susumu Kotake
    1995 Volume 38 Issue 1 Pages 1-7
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Owing to the progress of techniques and technology with high performance and high efficiency, fundamental understanding of their phenomena and functions from the elementary processes of molecular motion has increasingly been required. This leads to the introduction of "molecular mechanical engineering" which forms a bridge between microscopic molecular understanding (molecular science) and macroscopic continuum engineering (mechanical engineering). The former should be viewed not as an isolated science itself but as fundamental subsystems of the latter. With respect to "molecular mechanical engineering, " we discuss and review its scientific philosophy, how it will be developed and extended, and how it will contribute to further advances in mechanical engineering technology.
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  • Yasushi Takeda
    1995 Volume 38 Issue 1 Pages 8-16
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    The Ultrasonic Velocity Profile (UVP) measuring method has been developed at PSI. It utilizes pulsed ultrasonic echography together with the detection of the instantaneous Doppler shift frequency. This method mainly has the following advantages over the conventional techniques : 1) an efficient flow mapping process, 2) applicability to opaque liquids and 3) a record of the spatiotemporal velocity field. After a brief introduction of its principle, the characteristics and specifications of the present system are given. Then examples such as for oscillating pipe flow, T-branching flow of mercury and circular free jet flow in fluid engineering are described, which confirm the above advantages. In a further in-depth study of fluid dynamics, results of an investigation of modulated wavy flows in a rotating Couette system are presented. The position-dependent power spectrum and time-dependent energy spectral density were used in order to study the dynamic characteristics of the flow, and subsequently the velocity field was decomposed into intrinsic wave structure based on the two-dimensional Fourier analysis.
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  • Hiroyuki Miyamoto, Hideki Ohba
    1995 Volume 38 Issue 1 Pages 17-24
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Flow measurements were taken in unshrouded and shrouded centrifugal impellers with 10 radial blades at the outlet by using a five-hole pressure probe. Measurements were taken for a flow rate corresponding to nearly zero incidence angle, and two other flows with reduced and increased flow rates. It was shown by these measurements that, along the passage, the low-energy region tended to move from the middle blade-to-blade position toward the suction side near the casing surface in the unshrouded impeller, and from the suction-side/shroud corner toward the hub side in the shrouded impeller. These shifts of low-energy region were observed upstream in the passages of both impellers, as the flow rate decreased.
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  • Hiroyuki Miyamoto, Hideki Ohba
    1995 Volume 38 Issue 1 Pages 25-30
    Published: February 15, 1995
    Released: February 18, 2008
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    The characteristics of unshrouded and shrouded centrifugal impellers were derived from the impeller passage flow. Effects of flow rate on the characteristics were investigated for a flow rate corresponding to nearly zero incidence angle, and two other flows with reduced and increased flow rates. The following results were obtained as the flow rate decreased. The position of the largest blade load moves upstream in the impeller passage, but this movement in the unshrouded impeller is not as clear as that in the shrouded impeller. The absolute circumferential velocity and the total pressure tend to increase in the inlet-to-outlet passage, but these increases become smaller at the unshrouded impeller exit. Moreover, the static pressure increases in the passages of both impellers.
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  • Yoshiaki Yamauchi, Hitoshi Soyama, Yasunori Adachi, Kazunori Sato, Tak ...
    1995 Volume 38 Issue 1 Pages 31-38
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    In order to establish useful techniques of cutting, drilling, peening and flushing by high-speed submerged water jets, we systematically observe the eroded surface on aluminum-alloy specimens in relation to the characteristics of cavitating jets, especially for the impinging jet through lucite specimens, for several types of nozzles. The impulsive pressures induced by the cavitating jets are also measured by means of pressure-sensitive film. It is concluded that the erosion characteristics are quite different in two typical standoff distances, i. e., the 1st and the 2nd peak. Cylindrical, small and deep pits predominantly occur at the 1st peak, while small lots of plastic deformations predominantly occur in the 2nd peak. Therefore, the 1st peak is suitable for cutting, while the 2nd peak is suitable for peening.
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  • Seiji Shimizu
    1995 Volume 38 Issue 1 Pages 39-44
    Published: February 15, 1995
    Released: February 18, 2008
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    The evolution of a round turbulent jet issuing from a nozzle with a collar is simulated by using a discrete vortex method under the constraint of axial symmetry. The vortex sheets shed from the nozzle and the edge of the collar are represented by vortex ring elements. The collar is represented by vortex rings of appropriate strengths to satisfy the no-through-flow condition. The effect of the collar on the development of the jet shear layer is investigated with and without harmonic excitation. When harmonic excitation in the range of St=0.3 to 0.7 is applied to the model jet issuing from a nozzle without a collar, large-eddy structures corresponding to the frequency of the excitation are formed. When St≥0.5, these eddies coalesce immediately and are converted into eddies of St/2. The evolution of the jet shear layer is greatly affected by the collar. The preferred frequency varies with the dimensions of the collar.
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  • Yukimasa Oguri
    1995 Volume 38 Issue 1 Pages 45-50
    Published: February 15, 1995
    Released: February 18, 2008
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    When a fluid flows through a curved pipe, there exists a secondary flow, and the frictional resistance increases considerably compared to that of a straight pipe. Though the friction factor of curved pipes has been studied by many investigators theoretically and experimentally, few studies on three-dimensional coiled pipe flows have been conducted and the flow nature and the friction factors on these flows are yet unexplored. The purpose of this paper is to present the measured results on the hydraulic losses for the flow through tubular pipes coiled continuously in an 8-shape. It is confirmed that the friction factor in coils λn decreases with the increase in the number of turns of a coil n, and the flow in pipes reaches a saturated state in the first seven turns of the coils.
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  • Yasutaka Nagano, Masaya Shimada
    1995 Volume 38 Issue 1 Pages 51-59
    Published: February 15, 1995
    Released: February 18, 2008
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    With the aid of direct numerical simulation (DNS) data, we have constructed near-wall modeling of the dissipation-rate equation for a k-ε turbulence model. All the budget terms in the exact ε-equation are incorporated in the modeled ε-equation, and both term-to-term and overall comparisons of model predictions with the DNS data are performed. It is found that the wall region should be partitioned into at least two regions so as to reflect different mechanisms of the generation processes in the dissipation of turbulent kinetic energy. Pressure diffusions in the k-and ε-equations are found to be equally important and thus should be modeled. Comparisons of the resultant k-ε model with the DNS data of channel and boundary layer flows with and without pressure gradients show close agreement of various turbulent quantities. In particular, near-wall behavior of ε is reproduced with the present model very well.
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  • Yasuji Tsubakishita, Hiroyuki Hamana, Takao Yoshikawa
    1995 Volume 38 Issue 1 Pages 60-65
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A numerical analysis is developed for sound radiation from cylindrical ducts. The structure of the radiated field is numerically obtained for unflanged, flanged, and horned-type ducts, including the effect of mean flow field. The governing equation for acoustic disturbances is a linearized unsteady Euler equation about a steady compressible mean flow. The numerical simulation is conducted by a fourth-order accurate finite difference scheme. The present result for the reflection coefficient shows good agreement with the experiment and available theory. The results also show that a nonuniform mean flow reduces the sound pressure level, although this is not valid for a uniform mean flow.
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  • Hironori Naka, Hitoshi Soyama, Kentaro Sakagami, Risaburo Oba, Masahir ...
    1995 Volume 38 Issue 1 Pages 66-72
    Published: February 15, 1995
    Released: February 18, 2008
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    In order to improve the reliability of high-speed hydraulic machinery, detailed behavior of the violent vibrations appearing on a typically low-drag Eppler foil is systematically observed by means of high-speed stereophotography. We can clearly observe the following three types of violent vibrations : (i) the vibrations resulting from a singly-attached cavity, usually arising at a higher incidence αi, (ii) ones resulting from large travelling bubbles arising at a lower incidence, (iii) a mixture of these two types.
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  • Yoshiyuki Matsuno, Kazuki Ohshima
    1995 Volume 38 Issue 1 Pages 73-78
    Published: February 15, 1995
    Released: February 18, 2008
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    A magnetic fluid is a kind of multiphase fluid which consists of a stable colloidal dispersion of magnetic particles in a liquid carrier. The most basic factor governing its behavior is magnetic susceptibility. This paper describes the research on a measurement apparatus for magnetic susceptibility of a magnetic fluid by means of electromagnetic measurement. The apparatus is equipped with an electromagnet having a very low residual magnetization and magnetic field gradient adequate to secure a measurement of high accuracy. The measurement results of magnetic susceptibility with this apparatus are also reported for several kinds of magnetic fluids in various magnetic fields, temperatures and concentrations.
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  • Takashi Masuoka, Yasuyuki Takatsu, Shuji Kawamoto, Hidekazu Koshino, T ...
    1995 Volume 38 Issue 1 Pages 79-85
    Published: February 15, 1995
    Released: February 18, 2008
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    An experimental and analytical study is conducted on the effects of a horizontal porous layer on the development of the buoyant plume arising from a line heat source in an infinite fluid space. Visual observations and the experimental temperature distributions show the expansion and contraction of the plume at the lower and upper interfaces of the permeable layer. Similarity solutions assuming their proper virtual origins can approximately predict the changes of the plume width. Detailed numerical examination indicates that the lateral flow induced near the interfaces causes deviation from the similarity solutions. The vicinity of the interface is understood to be a transition region between the similarity solutions. The numerical analysis adopts the Beavers-Joseph slip boundary condition with the slip coefficient α estimated by α=1/√(ε), where ε is the porosity of the porous layer. The fairly good agreement between the experimental and numerical results confirms the validity of the slip coefficient.
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  • Katsuyoshi Kamakura, Hiroyuki Ozoe
    1995 Volume 38 Issue 1 Pages 86-91
    Published: February 15, 1995
    Released: February 18, 2008
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    When a two-layer system which consists of water (upper layer) and an aqueous solution (lower layer) is heated from a vertical side wall and cooled from an opposing side wall, convection starts in each layer. A Galerkin finite-element method was employed for the numerical analyses of the two-layer convection. Computations were carried out for the Prandtl number Pγ= 6, the Lewis number Le=100, the aspect ratio A=4, the Rayleigh number Ra=105 and the buoyancy ratio N=2, 5 or 10. In the case of N=10, the intermediate concentration stratified layer was formed between two convection layers. In the case of N=5, two interfaces with very steep concentration gradient developed both at the top and at the bottom of the intermediate layer, especially near the walls. Later, the two interfaces were unified to a single sharp interface. In the case of N=2, first a single sharp interface was formed and later the interface was degraded by the fluid streaming into the other layer. The thickness of the interface was experimentally found to be dependent on the buoyancy ratio, confirming these characteristics.
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  • Takeo Fukushima, Kenichi Yanagi, Kazumasa Mihara, Ritsuo Hashimoto, Ke ...
    1995 Volume 38 Issue 1 Pages 92-99
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    A simple and practical method is proposed to numerically analyze thermal deformation and contact width of a roll with a strip. This method is comprised of three processes which are coupled with each other and lead the roll temperature, the roll thermal deformation and contact width with the strip as the results of calculation. The operating conditions of a production line are used as the initial values of the analysis. The results for the roll temperature almost agreed with the measured one, and the new analytical method is shown to be adequate to predict thermal crown and temperature profile of the roll.
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  • Kee-Chiang Chung
    1995 Volume 38 Issue 1 Pages 100-107
    Published: February 15, 1995
    Released: February 18, 2008
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    The effects of one-surface and two-surface coatings on thermal contact conductance of contacting aluminum 6061-T6 surfaces were experimentally investigated through the use of metallic coatings prepared by the ion vapor deposition (IVD) process. Three different coating materials, aluminum, lead, and indium, were evaluated using two different coating thicknesses and two different surface roughnesses over the pressure range of 100 to 500 kPa, which is suitable for microelectronic application purposes. Experimental results are presented to graphically illustrate the dimension. less thermal contact conductance of one-surface coatings and two-surface coatings as a function of contact pressure. The thermal contact conductance was found to vary from 0 to 500 percent of the uncoated value, depending on the contact surface characteristics.
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  • Hideaki Yasui, Yoshiyuki Tsuda
    1995 Volume 38 Issue 1 Pages 108-113
    Published: February 15, 1995
    Released: February 18, 2008
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    ITO (indium tin oxide) thin films have been prepared by the magnetron sputtering method. The effects of plasma conditions on ITO thin-film properties have been investigated by means of the Langmuir probe method. Furthermore, the effects of substrate temperature have been investigated. The following results were obtained : (1) Polycrystal ITO thin films were prepared at 40°C substrate temperature. (2) High electron temperature (Te) is necessary for ITO thin-film crystallization. (3) The magnetic field plays an important role in generating high-Te plasma.
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  • Takeo Takashima, Yoshihiro Iida
    1995 Volume 38 Issue 1 Pages 114-120
    Published: February 15, 1995
    Released: February 18, 2008
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    The spontaneous vapor explosion generated by single drops of molten tin submerged in water is investigated using high-speed photography and pressure trace measurement. The vapor film begins to collapse at the edge of the disk-shaped drops and the collapsed zone spreads over the rest of the drop at a velocity of several meters per second. Explosion experiments in a two-dimensional channel with a narrow space are also carried out to observe more clearly the explosion configuration and the fragmentation process. A model of the spontaneous vapor explosion with a single drop is presented on the basis of experimental observations. In this model, the size of the vapor bubble compared with the cloud of high-temperature debris is assumed to have a strong relationship with heat transfer, and the collapse of the vapor bubble is also assumed to be induced by overexpansion and condensation.
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  • Sung Sik Chung, Osamu Kawaguchi
    1995 Volume 38 Issue 1 Pages 121-128
    Published: February 15, 1995
    Released: February 18, 2008
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    A series of evaporation rate constants has been obtained for fine free droplets of paraffin hydrocarbons, n-heptane, iso-octane and n-undecane in the range of 623 to 1023K in temperature and 0.1 to 0.5 MPa in pressure as the ambient conditions. To obtain the time histories of droplet diameter a fine droplet stream generated by an electrically controlled piezoelectric element was synchronized with a flash light, and enlarged droplet images were taken on a still camera. The evaporation rate constant increases with ambient pressure and temperature and is expressed by empirical equations. A mixed-hydrocarbon droplet of n-heptane and n-undecane was also examined in terms of the evaporation rate constant, and the evaporation history, the so-called D2-t relation, displays a bending line with two separate straight lines of respective constituents.
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  • Hiroshi Hattori, Motoo Ota, Eiichi Sato, Toshikazu Kadota
    1995 Volume 38 Issue 1 Pages 129-135
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    An experimental study has been carried out on the combustion characteristics of a newly proposed direct-injection stratified-charge SI engine. A water-cooled, 4-cylinder, 4-stroke-cycle diesel engine with a square piston cavity was modified to permit the installation of a spark plug. Charge stratification was accomplished with two-stage fuel injection. The main fuel was injected at the early stage of the induction stroke to form a lean homogeneous mixture, and the auxiliary fuel was injected just before the spark firing to produce a rich mixture near the spark plug. The results showed that the lean limit was extended up to approximately the air-fuel ratio of 25 without increasing in fuel consumption and HC emissions. The optimum quanTITY of auxiliary fuel was found to extend the lean limit and to reduce the fuel consumption. Charge stratification caused a reduction in the ignition delay.
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  • Chihong Liao, Kunio Terao
    1995 Volume 38 Issue 1 Pages 136-142
    Published: February 15, 1995
    Released: February 18, 2008
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    In order to determine the general aspect of the spontaneous ignition in a fuel spray injected in compressed air at high temperature, which takes place usually in diesel and pulse jet engines, an experimental method using a shock tube is developed. A shock wave driven by high-pressure He gas propagates in the air in the low-pressure tube and reflects at a shock tube end. Through application of the pressure of the shock wave at reflection, n-octane fuel is injected into the air behind reflected shock waves in the shock tube. The fuel injection space is optically separated into 5 regions in the vertical direction, and the induction period of spontaneous ignition in each region is separately observed. As the induction period fluctuates markedly, the measured results are treated statistically and analyzed on the basis of the stochastic ignition theory.
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  • Yoshishige Ohyama, Kotarou Hirasawa, Yutaka Nishimura, Minoru Ohsuga, ...
    1995 Volume 38 Issue 1 Pages 143-148
    Published: February 15, 1995
    Released: February 18, 2008
    JOURNALS FREE ACCESS
    Pulsating flow characteristics of the hot-wire air flow meter for gasoline fuel injection systems were investigated to analyze simple methods for processing measured data. It was clarified that backward flow components due to pulsation are detected as forward flow by the probe in conventional meters, which increases errors. The errors due to pulsation can be reduced by using a meter with a hot-wire probe located in a bypass passage, which aerodynamically compensates forward and backward flow components.
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