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Tameo NAKANISHI, Sensho USAMI, Katsuyoshi SUZUKI, Keizo KANEKO
Article type: Article
Pages
299-300
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Three-dimensional computation on the interaction of the internal flow and the oscillating surface of a piezoelectic pump has been carried out. A general flow solver based upon the multi-domain method and the semi-Lagrangian time integration method was employed to solve the viscous flow inside the pump. The oscillating surface was modeled to account for the effects of the mass, the elasticity, the dumping factor, the pressure difference and the piezoelectric force. Computations were conducted for piezoelectric forces of different frequency. The details of the interaction of the internal flow and the surface were clarified. The frequency, which results in the maximum deformation of the surface as well as the flow rate, was determined.
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Akio IKEBATA, Feng XIAO
Article type: Article
Pages
301-302
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper reports the development of a CFD code for multi-fluid simulations with a newly devised conservative and non-diffusive front-capturing scheme. In the front-capturing scheme, which is so called STAA (Surface Tracking by Artificial Anti-diffusion) method, the volume of fluid (VOF) function is firstly transported with a conservative advection scheme, such as PPM and CIP-CSLR. Then, the diffused VOF function is corrected with a well designed artificial flux to eliminate the numerical smearings. Our numerical tests show that the STAA scheme performs satisfactorily in geometrical accuracy, conservation and numerical dispersion. STAA scheme is readily applied to multi-fluid simulations when incorporated into a C-CUP based model.
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Tomofumi Saito, Takao Kitagishi, Tetsuro Tamura, Makoto Tsubokura, Mas ...
Article type: Article
Pages
303-304
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Numerical prediction of aerodynamic sound is required to reproduce with sufficient accuracy to the fluctuating component of a flow field and a pressure field. In this research, LES was applied to the flow field around a two dimensional rectangular cylinder and compare with upwind finite difference method. The flow field were reproduced with high precision and the parameters which governs aerodynamic sound were evaluated. Consequently, the usefulness of LES was shown from the point of the correlativity of pressure of the spanwise direction.
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Takao NAGASAKI, Yutaka ITO, Hirokuni AKIYAMA
Article type: Article
Pages
305-306
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A numerical analysis was performed on the flow and mass transfer of counter-current water and gas flows in a vertical parallel plate channel. In order to deal with the moving gas-liquid interface, boundary-fitted coordinates were employed both for water and gas phases. A sinusoidal disturbance was added to the initial smooth film. It was found that the smooth film is unstable resulting in a fully developed solitary-like large wave. A circulating flow exists in the large wave which enhances the mass transfer. The enhancement is more remarkable for the mass transfer in liquid with high Schmidt number. With the increase of the gas velocity the wave height increases, and the circulating flow in the wave becomes more complicated one due to the shear force by the gas flow.
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Tomonari KOBAYASHI, Toshihiro KAWAGUCHI, Toshitsugu TANAKA, Yutaka Tsu ...
Article type: Article
Pages
307-308
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A discrete particle model for flows of Geldart's Group A particles is investigated. It is known that Group A particles have a characteristic flow regime (homogeneous regime) in fluidized beds. It is found that the present simulation predicts the homogeneous regime and the hysteresis behavior in the bed pressure drop. By analyzing the stress chain in the particles bed, it is shown that the hysteresis behavior is caused by a change in the stress distribution in the particles bed.
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Kenya KUWAGI, Hiroshi TAKEDA, Masayuki HORIO
Article type: Article
Pages
309-310
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A novel method for giga-scale DEM simulation was derived. The method is based on the motion equation for particles keeping the local particle assembly similar. The motion of multiple particles whose diameter, density and chemical composition are the same is represented by one particle called a representative particle. This method can be accordingly called'a representative particle model'. A representative particle occupies the same volume as the one of the represented particles and has the same density and chemical composition. This model can be applied even for cohesive particles and non-uniform size particles. The present model was validated by carrying out numerical simulations for particles of 2 densities. From the comparisons between the results with and without the model, the effectiveness of the model was confirmed.
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Ryoichi KUROSE, Hisao MAKINO
Article type: Article
Pages
311-312
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Three-dimensional large eddy simulation (LES) is applied to a turbulent jet flame of a solid fuel, and the interactions among the dispersion, evaporation and combustion of the solid-fuel particles are investigated. It is assumed that the solid-fuel particles evaporate dependent on the temperature prior to reacting, and that the chemical reaction with heat release of the fuel vapour and oxidizer takes place in the continuous phase. The results show that the radial profiles of the mean axial gas velocity, product mass fraction and temperature tend to correspond to the Gaussain profile in the jet center region, but deviate from it in the jet edge region. Also, the radial distance, which shows the maximum particle number density, for Ce=3.0 moves outward earlier than those for Ce=0 and 1.0.
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Yingkang PAN, Toshitsugu TANAKA, Yutaka TSUJI
Article type: Article
Pages
313-314
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Direct numerical simulations (DNS) of particle-laden curved turbulent channel flows at the Reynolds number 2990 based on centerline mean velocity and the channel half-width H and mild curvature (H/r_c=0.0127) on a 128×64×128 grid were p4erormed using the finite difference method (FDM). Particles were traced using the deterministic method combined with the direct particle interactions via hard-sphere collisions and two-way coupling. Particle volume fractions from O ((10)^<-6>) to O((10)^<-5>) were considered. Special particle structures near the wall are formed. Particles have significantly affected the structures of Taylor-Goertler vortices. It is also found that the turbulence structures near the wall are modified due to local particle concentration.
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Tomomi UCHIYAMA, Yoshinobu KITANO
Article type: Article
Pages
315-316
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This study is concerned with the numerical analysis of particulate jet generated by solid particles falling from a slit orifice into an unbounded quiescent air. A two-dimensional vortex method, proposed for the simulation of particle-laden free turbulent flow in prior papers, is employed for the analysis. The falling particles induce complicated air jet involving large-scale eddies around the jet. The air takes its maximum velocity at the center line of the jet. The effect of the particle diameter on the velocity distributions of the air is investigated. The entrained air flow rate is favorably compared with the value predicted by an analytical model.
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Toshitsugu TANAKA, Yoshitaka IDE, Goshi AKIYAMA, Yutaka TSUJI
Article type: Article
Pages
317-318
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Particle clusters formed in gas-solid flows in risers of circulation fluidized beds or in pipes of pneumatic transport system have much influence on various kinds of transport phenomena. In the present study, the structure of the flow with clusters is investigated numerically. The Lagrangian/Eulerian approach and the two-way coupling are applied because of the large effect of the solid phase onthe gas flow. The gas flow was solved based on the N-S equation. the motion of individual particles is calculated taking into account particle-particle collisions by a deterministic method. The effects of distribution of particle diameter on the cluster structure is studied. The calculated results are compared with experimental ones measured in a vertical duct with respect to the fluctuation of local solid volume fraction and the spatial structure of the clusters.
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Tatsuo USHIJIMA, Osami KITOH
Article type: Article
Pages
319-320
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Particle response to the spatial structure of isotropic turbulence has been studied, in order to improve the model prediction of particle dispersion in turbulent flows when characteristic scales of flow field and particle are comparable. It is found that any particle would be transfered into a low vorticity region by the spatial structure of turbulence. However, effect of the spatial structure is limited to a certain range of time scale, because of different response to the spatial structure and time scale of turbulence.
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Hiromi UEDA, Rentaro KANZAWA, Shigeo HOSOKAWA, Akio TOMIYAMA
Article type: Article
Pages
321-322
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Sufficient knowledge of bubble-induced turbulence (B.I.T.) is indispensable to develop an accurate turbulence model in a gas-liquid two-phase bubbly flow. In this study, we measured turbulence intensities and Reynolds stresses in air-water bubbly flow in a vertical pipe under the condition of a low liquid Reynolds number (Re=900). To enable the LDV measurement of Reynolds stresses, we could confirm that (1) turbulent kinetic energy of B.I.T. is proportional to local void fraction, (2) the ratio among axial, radial and azimuthal components of turbulence intensity is 2 : 1 : 1 and (3) the Reynolds shear stress of B. I. T. is well correlated with the void fraction gradient.
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Toshio SASAKI, Masaaki ISHIKAWA, Yuichi MURAI, Fujio YAMAMOTO
Article type: Article
Pages
323-324
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Numerical and experimental investigations on bubbly channel flows through closely arranged cylinders have been carried out. This paper concerns with the results of the three-phase simulation using Eulerian-Lagragian model in which the cylinder-bubble interaction model is taken into account. The results show that rising velocity of bubbles decreases due to the bouncing of the bubbles at the cylinder surface, and the characteristic scale of the liquid flow is altered with the arrangement patterns of the cylinders.
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Shuji Yamamoto, Hidesada Tamai, Akio Tomiyama, Shigeo Hosokawa
Article type: Article
Pages
325-326
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A three-dimensional one-way Bubble Tracking Method has been proved to give good predictions for the spatial evolution of flow pattern, mean void fraction, void fluctuation, mean pressure drop and pressure drop fluctuation in developing bubble flows in vertical pipes. In this study, the spatial evolution of radial developing bubble flow. As a result, it is confirmed that the method gives good predictions of local void fractions, provided that bubble size distributions at an inlet were available.
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Kenichi SUGIOKA, Kenji TANNO, Kouji NAGATA, Satoru KOMORI
Article type: Article
Pages
327-328
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Sea-water droplets are produced by wave-breaking owing to high wind-shear over the sea surface in a wind-wave tank. The contribution of the droplets to the mass transfer between air and sea has not been clarified. The dispersion mechanism of the droplets was, therfore, investigated under high wind-speed condition with wave-breaking. Droplet diameter and velocity were simultaneously measured using a phase Doppler anemometer (PDA). The results show that the relative velocity between droplet and ambient air depends on the wind-speed and droplet diameter. Horizontal flux of the droplet depends on air friction velocity on the air-water interface, the height from the interface and the droplet diameter. The particle Reynolds number and the horizontal flux of the droplet can well be correlated with these quantities.
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Takayuki OKA, Takenori MATSUBARA
Article type: Article
Pages
329-330
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this paper, the aerodynamic performances of some 2-dimensional Joukowsky airfoils under the ground effect are evaluated through the finite element method analysis. There are derived the effective forms in term of the lift-drag ratio for the wing-in-ground-effect. Especially, the variation of lift-drag ratio depends greatly on the bottom side shapes of the airfoils. The following form of airfoils are selected as the small camber ratio and the thin thickness ratio, which would take in more air flow in the bottom side at small angle of attack.
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Tomoharu KONDO, Takenori MATSUBARA
Article type: Article
Pages
331-332
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Equations for evaluating the lateral-directional stability in steady rolling motion of high-speed for wing-in-ground-effect crafts were formulated. The crafts may consist of arbitrary number of wings within or out of ground effect. Small perturbations superposed on the steady rolling motion of the craft were assumed and were linearized in comparison with the steady rolling motion. The parametric studies on the effect of sizes and locations of the vertical tails of the boat on the stability have given reasonable performances and tendencies.
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Takashi YUZAWA, Yoshifumi OGAMI
Article type: Article
Pages
333-334
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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A tailless aircraft is known as an airplane with the merit of little air drag since the tail and the fuselage, which connects the main wing with the tail plane, do not exist. It also has the demerit of instability in maneuvering in the longitudinal direction. Our team at Ritsumeikan University has been daring to participate in the birdman-rally with the tailless aircraft, but a good result has not yet been obtained. The purpose of this paper is to study and to develop the tailless aircraft for the birdman-rally by computational fluid dynamics. The data of the flight at the last rally were analyzed, and the problems and solutions were obtained.
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Yusuke NISHIZAKI, Akira URITA, Shuji TANAKA
Article type: Article
Pages
335-336
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Aerodynamic characteristics and near-field flow fields of rectangular flat-plate wings with very small aspect ratios, λ=1∿0.05 at full angles of attack, α=0∿90 deg, have been presented. The flow details were investigated using oil film flow visualization and PIV measurements. The typical features of surface flows on wings with various aspect ratios can be classified into 6 types, i.e., un-separated(US), partially separated(PS-1) with U-type flow reattachment, PS-2 with O-type reattachment, PS-3 with long cigar-type reattachment, PS-4 with indistinct reattachment and fully separeted(FS). The aerodynamic characteristics and near-flow structures of test wings can be classified into three groups corresponding to their aspect ratios, which are (1) small aspect ratio wing (λ=1), (2) smaller aspect ratio wings (λ=0.75∿0.66) and (3) very small aspect ratio wings (λ=0.5∿0.05). It has been confirmed that the aerodynamics and detailed flow structures investigated exhibit very close correlations.
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Tomohiro SONE, Akira URITA, Shuji TANAKA
Article type: Article
Pages
337-338
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Detailed aerodynamic characteristics and near field flow structures of delta wings with aspect ratios λ=1.28∿4 at angles of attack α=0∿90° have been presented. In high angle of attack regions near α_C_L_<max>, flow details for small λ, (1.28∿2), are mostly similar to each other, which leads to the similar values of α_C_L_<max> and C_L_<max>, whereas reattached flow regions for aspect ratios (2.4∿4) are severely affected by λ, then α_C_L_<max> and C_L_<max> decreases with and increase in λ. In full-stalled regions (α>50deg.), entirely separated flows appear all over the suction surfaces irrespective of λ, then C_L and C_D can be represented by sinα and cosα of the (C_D)_<α=90>. In intermediate regions between them, highly unsteady natures, in which longitudinal and ring-type vortices are alternatively formed, then aerodynamics are changed with α corresponding to the fraction ratio of the both vortex types.
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Jinya FURUI, Masahiro NANBA, Yoichi HIRAMORI, Kazuo MATSUUCHI, Masahik ...
Article type: Article
Pages
339-340
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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We examined the drag and thrust efficiency of two airship models with a stern propeller. There is a interaction between the airship hull and the propeller. To obtain an understanding of the interaction, we measured the form drag of the airships with and without a propeller, and calculated the propeller efficiency and the total efficiency of airships. We also compared the results for two airships. Furthermore we carried out inviscid computation for the effect of the propeller on airship efficiency. It was clarified that there are two patterns for the direct effect of the propeller on the pressure on the hull surface. One is good for the airship hull and the other is undesirable.
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Tomonori HORIUCHI, Hiroyuki TAKAHIRA
Article type: Article
Pages
341-342
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In the present study, we developed a three-dimensional numerical method based on the level set method that can be applicable to the two-phase systems with high-density ratio. In the level set method, we must reinitialize the level set function to keep the level set function as a true distance function. To achieve the perfect mass conservation of two fluids systems, we modified the reinitialization procedure developed by Sussman et al. We simulated the coalescence of two rising bubbles under gravity to evaluate the mass conservation for the present method. We succeeded in simulating the bubble coalescence when the density ratio between the gas and the surrounding liquid is 0.001. It is shown that the mass conservation of bubbles is very well even after the bubble coalescence.
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Satoru USHIJIMA, Iehisa NEZU
Article type: Article
Pages
343-344
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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An implicit numerical algorithm (C-ISMAC method) has been proposed for incompressible flows with a collocated grid system. The C-ISMAC method, which is based on an implicit SMAC method proposed for staggered grid system, enables us to utilize higher-order schemes for discretization as well as to largely decrease the necessary computational time. This method was applied to cavity flows with a fifth-order QSI scheme for convection terms. As a result, it was shown that the computational speed becomes two to three times faster than a usual explicit method and that the computational accuracy of the QSI scheme is still preserved in the C-ISMAC method.
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Shinya TAKEUCHI, Masayoshi OKAMOTO, Nobuyuki SHIMA
Article type: Article
Pages
345-346
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Large eddy simulation (LES) with a one-equation-type subgrid scale model proposed by Okamoto-Shima is performed for turbulent flow through concentric annuli. The low-level turbulence quantities and shear stress budget in the inner region are well reproduced by the present LES. However, due to coarse grid resolution, there are disagreements between the DNS and LES results in the outer region.
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Mikikane HIROHATA, Nobuyuki TANIGUCHI, Toshio Kobayashi
Article type: Article
Pages
347-348
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this paper, We introduce model for the LES of lifted non-premixed jet flames based on 2 scalar flamelet modeling. The flamelet G-equation for premixed combustion and the conserved scalar equation for non-premixed combustion are combined to express partially premixed flame propagation. The calculation results are shown that wrinkling lifted flames are simulated and the lift-off height can be predicted. This method will be useful to investigate the flame stabilizing mechanism or flame controls of non-premixed jet flames.
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Katsuya INOUE, Mikikane HIROHATA, Nobuyuki TANIGUCHI, Toshio Kobayashi
Article type: Article
Pages
349-350
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this research, a Large Eddy Simulation (LES) of hydrogen jet non-premixed flame was carried out and a prediction method for nitric oxide (NO) applicable to LES was proposed. Combustion model in LES is based on conserved scalar approach and laminar flamelet model. In NO prediction method, NO source term is calculated using temperature and species concentration predicted by LES and the transport of mass fraction of NO is calculated as a passive scalar, which does not affect flow field. Computed results were found in overall agreement with experimental data in velocity and temperature field. The trend of distribution of NO concentration was predicted reasonably by using this method, however the amount was underestimated.
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Takahiro YASUDA, Atsushi OKAJIMA, Minoru MORIYOSHI
Article type: Article
Pages
351-352
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Flow around a rectangular cylinder in oscillatory flow was studied by a numerical simulation using a finite-volume method. The computations were carried out through Keulegan-Carpenter number(KC) in the range of 3≦KC≦ 12 at Stokes number (β)=95 in the case of D/H=0.6,2.0. At KC=3 and 4,longitudinal vortices arrange periodically along the axis of the cylinder were predicted in both cases of D/H=0.6 and 2.0 such as in the case of circular and square cylinder. For D/H=0.6,at KC=12,"transverse-vortex street" obtained in circular cylinder was also predicted. The characteristics of fluid-dynamic forces were in good agreement with experimental results.
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Yasuhiro ASANO, Chuichi ARAKAWA
Article type: Article
Pages
353-354
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The results of the experiments of Tokumaru & Dimotakis (1991) have shown that the drag forces acting on a circular cylinder in rotary oscillation decrease up to 80% compared with stationary one. In the past, some researchers have tried computational studies for this phenomenon, but these predictions do not agree with each other. In the present study, three-dimensional turbulent simulations with the LES model were carried out on the Hitachi SR2201 in order to verify the drag reduction effect of the flow around a circular in rotary oscillation.
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Kazuo HARA, Masahiro INOUE
Article type: Article
Pages
355-356
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Secondary (negative) vorticity is frequently observed at the up-wash side of the lateral vortex interacting with a wall. The generation of the secondary vorticity is found to be due to the process term of the vorticity equation in which transversal vorticity component of the lateral vortex is converted into negative vorticity by the combination of velocity gradient. In the secondary vortex region, the process term provides positive vorticity which attenuate the vorticity of the secondary vortex.
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Manabu ODA, Yoshihisa YAMAMOTO, Masato FURUKAWA, Masahiro INOUE
Article type: Article
Pages
357-358
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The Karman vortex was controlled by minutely vibrating the side plates of a square cylinder, and the suppression of the fluid-dynamic forces acting on the square cylinder was made. Two excitation modes were employed : the identical phase mode in which all the side plates vibrate at the same phase, and the opposite phase mode in which side plates divided at the center of span vibrate with 180 degree differential phase alternately. As a result, the former mode can reduce the averaged drag and the later mode can reduce fluctuating lift.
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Yasuaki KOZATO, Shigeki IMAO, Toshio TANAKA, Seiichi HAMAJI
Article type: Article
Pages
359-360
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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This paper presents an experimental investigation of a flow around a circular cylinder with an external periodic disturbances. Phase averaged velocity based on the fluctuating surface pressure were measured to clarify the effect of the excitation on the vortex shedding process. The frequency of the vortex shedding and the convective velocity of the vortex structure are slightly changed by the excitation.
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Yoshifumi YOKOI, Susumu INAGAKI, Takahiro OYAMA
Article type: Article
Pages
361-362
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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In this study, the flow features of vortex shedding from a circular cylinder forced-oscillating in the in-line direction were investigated by use of flow visualization technique at the Reynolds number Re=570,with four kinds of amplitude ratio (2a/d=0.25,0.5,0.75 and 1.0) and the range of oscillation frequency ratio f/f_k=0.18∿6.2. As a result of the experiments, it was found that when the oscillation amplitude ratio 2a/d becomes large, the lock-in range expands widely and even if the cylinder oscillation frequency is smaller than the natural Karman vortex shedding frequency, the lock-in phenomenon arises. The distribution of flow pattern in the lock-in range was shown. Two deferent flow patterns in the lock-in state of twin vortex shedding were observed. One of which was inside curl type and the other was outside curl type.
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Takamitsu BABA, Tomoko TSUCHIYA, Teruo KUMAGAI
Article type: Article
Pages
363-364
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Free-fall motions of a single sphere near various walls are investigated in detail in order to discuss the hydrodynamic interactions of two spheres. The superposition method of Oseen's flow is improved to satisfy the boundary conditions of various walls. When the distance between the shpere and the various walls is more than 1.0 times the sphere diameter, the numerical results obtained by using the improved superposition method of Oseen's flow field agree well with the experimental results, The Oseen's collcation method using the higher order solution to Oseen's equation is newly constructed. When the distance between two spheres is more then 1.5 times the sphere diameter, the numerical results obtained by using the newly constructed collocation method agree well with the experimental results.
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Shigeki IMAO, Yasuaki KOZATO, Toshio TANAKA, Kazuhiro MURASE
Article type: Article
Pages
365-366
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Taylor vortex flow of drag-reducing solutions such as polymer solutions and surfactant solutions between concentric cylinders with the inner cylinder rotating and the outer one at rest has been investigated by mean of flow visualization. The radius ratios used hear are 0.858,0.909 and 0.975. Three kinds of polymer solution and a surfactant solution are used, all of which show remarkable drag reduction in the turbulent region. Critical Reynolds number at which Taylor vortex appears decreases with an increase in the concentration of additives, whereas critical Reynolds number at which Taylor vortex becomes wavy increases. Moreover, new flow patterns are observed that never appeared with a Newtonian fluid.
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Yuuki ONO, Yoshifumi OGAMI
Article type: Article
Pages
367-368
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The researches on μ-TAS have been made in the medical and chemical fields. Since the Reynolds number is so small in this device that the effective mixing by turbulence does not occur. To increase the mixing performance, we plan to use the optical micro-rotor, which rotates by a laser beam, as a mixing device in μ-TAS. The performance of the rotor, located at the midst of Y-shaped micro channel, to mix two kinds of fluids is studied by CFD. Using marker particles with random walks, the partial mixture ratio is calculated in each block arranged on the outlet boundary of the channel. It is found that in order to mix the fluids with the highest degree, the ratio of the inlet speed and the rotor tip speed should be almost 0.2.
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Teruo KUMAGAI, Ryota NAKASAKI, Muhetaler SADEER
Article type: Article
Pages
369-370
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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The desertification is regarded as one of the global subjects in 21th century, because the area up to approximately 6 million ha has been desertified every year. In this paper the behavior of sand surface behind a square block in a wind tunnel is observed using a high-speed video-camera with 10000 frames/s. The velocity profiles are measured using a Pitottube for the boundary layer flow in the wind tunnel. The sand sizes are 0.18∿1.00mm. The initiation of sand flight depends on the sand size, the sand density, the wind velocity and the angle between the sand surface and the flow direction. The sand ripples are formed after the initiation of sand flight in a turbulent boundary layer flow. Relatively larger sands are forcussed on the mountain side of the sand ripples, while relatively smaller sands are on the valley side.
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Hiroshige KUMAMARU, Satoshi KODAMA
Article type: Article
Pages
371-372
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
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Three-dimensional numerical calculations have been performed on liquid-metal magneto-hydrodynamic (MHD) flow through a rectangular channel in the inlet region of a magnetic field, including a region upstream the magnetic field. The continuity equation, the momentum equations and the induction equations have been solved by the finite difference method. As the gradient of the magnetic field becomes steeper, the pressure peak in the inlet region becomes larger; however there is almost no change in the total pressure drop. When the aspect ratio of the channel cross section becomes smaller, the total pressure drop through the inlet region becomes smaller.
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Nobuyuki KIMURA, Hiroyuki MIYAKOSHI, Minoru IGARASHI, Hideki KAMIDE
Article type: Article
Pages
373-374
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
CONFERENCE PROCEEDINGS
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A quantitative evaluation on thermal striping, in which temperature fluctuation due to convective mixing causes thermal fatigue in structural components, is of importance for reactor safety. It is necessary for understanding of thermal striping phenomena to evaluate transfer of temperature fluctuation from fluid to structures. Decrease of fluctuation amplitude is expected in the process of heat transfer from fluid to structure. In this study, a sodium experiment of parallel triple jets configuration was performed in order to evaluate transfer characteristics of temperature fluctuation from fluid to structure. As for the experimental geometry, a cold jet on the center and two hot jets on both sides flowed vertically and along the wall. As the results, it was shown that the non-stationary heat transfer characteristics could be represented by a heat transfer coefficient, which was constant in time. The heat transfer coefficients were correlated to the 0.8 power of Peclet number.
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Article type: Appendix
Pages
App2-
Published: September 20, 2002
Released on J-STAGE: August 01, 2017
CONFERENCE PROCEEDINGS
RESTRICTED ACCESS
