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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

The present paper describes the discrete particle simulation of the evacuation dynamics. The inter-pedestrian forces are given by the discrete element method (DEM). The composite particle model is proposed to take into account the effect of the non-circular shape of pedestrians on the evacuation behavior. It has been indicated that the pedestrians can evacuate faster when an obstacle is placed at an appropriate position. The effect of the obstacle on the evacuation rate is also examined numerically in the present study. The proposed numerical model represents the positive and negative effects of the obstacle on the evacuation behavior qualitatively. (C) 2014 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.trpro.2014.09.048

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A discrete particle model for flows of Group A particles in Geldart's classification is studied. In general, Group A particles are fine and light, so that the adhesion force has a strong effect on their fluidization behavior. Inter-particle adhesion force of Group A particle was measured first. Secondly, the DEM-CFD coupling simulation with the measured adhesion force was performed, and the simulated results were compared with the experimental data about a small-scale fluidized bed for verification of the simulation. It was found from the results that there were considerable differences between their flow patterns. In order to reveal the cause of the differences, the effect of the adhesion force in the contact force model was studied on the motion of a single particle colliding with a wall.
From the analysis on the particle-wall collision process, it is found that the spring constant used in the DEM model has a large effect on the particle's sticking behavior on the wall. The dynamic adhesion force model is proposed based on the present analytical investigation, and it is found that the present model well expresses the effects of the adhesion force on the flow structure for the case of a small adhesion effect. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.powtec.2013.02.028

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Language：Japanese   Publishing type：Research paper (scientific journal)  

A DEM-MPS coupled model for solid-liquid two phase flows is developed. Fluid motion is calculated for locally phase-averaged variables. The present model is applied to a collapse behavior of the assembly of aluminum particles in a rectangular container with and without liquid. The corresponding experiment is performed to validate the present model. The trajectory of each particle is traced by using the PTV (Particle Tracking Velocimetry) measurement. Calculated collapse behaviors agree well with the observed behaviors in the corresponding experiment. The calculated horizontal position of leading particle and particle velocity also agree well with the experimental results. © 2012 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.78.276

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Language：Japanese   Publishing type：Research paper (scientific journal)  

An NMR (Nuclear Magnetic Resonance) imaging technique was employed to visualize the convective motion in a horizontally vibrated granular bed. The size segregation phenomena are observed for a binary mixture of larger and smaller particles. Temporal progress of the size segregation was evaluated for three different combinations of binary mixture. The convective motion was clearly observed by MRI, that is, the smaller particles tended to fall down along the side wall, while the larger particles tended to rise through the central region. The convective motion is observed even in the plane perpendicular to the vibration direction as well as in the plane parallel to the vibration direction for all combinations of binary mixture. It was suggested that the size ratio of larger to smaller particles and of vessel to particle affected the segregation phenomena. © 2011 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.77.2227

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Generally, it is difficult to observe, without any disturbance, flow structures or velocities inside flows such as granular flows, particle-fluid flows and so on. It is effective to use a non-contact and non-destructive measurement method for such flows. In the present paper, an MRI (Magnetic Resonance Imaging) technique is employed to measure the motion and velocity inside the flows. MRI has been applied to granular flows since about 1990. Our group has studied the particle motion inside the rotating drum using MRI. The rotating drum is industrial equipment which is widely utilized in engineering processes. In the cylindrical rotating drum it is well-known that axial and/or radial segregation take place. In the present study, we use a conical rotating drum which is sometimes employed in the granulation process. The conical rotating drum is half-filled with a mixture of two different sizes of spherical particles. We varied the rotational speed. Then we investigated the effect of the rotational speed on the axial segregation pattern and observed the flow mode. (C) 2010 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.flowmeasinst.2009.12.007

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is difficult to apply optical techniques to the velocity measurement of the fluid-particle flows, especially when the volume fraction of particles becomes high, hi the present paper, the MRI (Magnetic Resonance Imaging) measurement is applied to dense liquid-particle flows. The velocity distribution of the liquid-particle flow is measured non-invasively by the phase method.

DOI： 10.1299/jsmemecjo.2010.7.0_131

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

A DEMCFD-coupled numerical simulation of the 2D fluidized bed with heat transfer is performed. The measurement of the temperature distribution of particles using the infrared thermography is also conducted to validate the heat transfer models. In the simulation, various heat transfer processes are considered, such as the heat transfer due to gas convection and the convective motion of the particles, the gas-particle and gas-wall heat transfer, the particle-particle or particle-wall heat transfer due to contact and turbulent heat diffusion. In the experiment, spherical aluminum particles of 3.14 mm in mean diameter are used. The air at the room temperature was sent to hot particle bed at about 150°C through the nozzle located at the center of bottom of the vessel. The comparison of the particle temperature distributions of the experiment and the simulation shows that agreement is good in the region wall effect is small, but not good region the wall effect is relatively large.

DOI： 10.1299/kikaib.75.753_1041

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmekansai.2008.83._10-8_

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Publishing type：Research paper (scientific journal)   Publisher：The Society of Powder Technology, Japan  

DOI： 10.4164/sptj.44.198

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASCE-AMER SOC CIVIL ENGINEERS  

The interaction between soil particles and pore water makes the behavior of saturated and unsaturated soil complex. In this note, upward seepage flow through a granular material was idealized using a one-column particle model. The motion of the individual particles was numerically simulated using the discrete-element method taking the interaction with the fluid into account. The fluid behavior was simulated by the Navier-Stokes equation using the semi-implicit method for pressure-linked equation. This approach has already been applied in powder engineering applications. However, there are very few studies that have used this approach in geotechnical engineering. This note first describes the qualitative and quantitative validation of this method for hydraulic gradients below the critical one by comparing the results with an analytical solution. Then, the ability of the method to simulate the macroscale behavior due to the interaction between particles and pore water at hydraulic gradients exceeding the critical hydraulic gradient is discussed.

DOI： 10.1061/(ASCE)1090-0241(2007)133:1(104)

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Language：Japanese   Publisher：The Society of Powder Technology, Japan  

It is difficult to measure a particle motion inside a dense granular flow or a fluid-particle flow because of the existence of other particles. MRI is one of the non-invasive measurement techniques for such flows. MRI can measure the velocity distribution (tagging method and phase method), which is an outstanding advantage of the MRI measurement. This paper briefly explains the principle of the MRI measurement. Then MRI is applied to some dense granular flows or fluid-particle flows, such as rotating drums, vibrated granular beds, hopper flows and spouted beds.

DOI： 10.4164/sptj.44.276

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Publisher：The Society of Powder Technology, Japan  

DOI： 10.4164/sptj.44.393

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Language：Japanese   Publisher：The Visualization Society of Japan  

DOI： 10.3154/jvs.27.107_240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

It is generally difficult to measure the particle motion inside of dense granular flows or fluid-particle flows. In the present paper, an MRI (Magnetic Resonance Imaging) technique is employed to measure the granular motion inside a rotating horizontal drum. A horizontal drum is half-filled with a mixture of two different sizes of spherical particles, and is steadily rotated along its axis. A typical radial segregation phenomenon, i.e., smaller particles concentrate to the central part and larger particles distribute in the peripheral part, was observed in vertical cross sections. When a tapered drum was used, in addition to the radial segregation, an axial segregation was also observed. The effect of the inclination angle of the drum wall on the segregation phenomena was studied. Furthermore the effect of the rotational speed on the axial segregation phenomena was also studied.

DOI： 10.1002/ppsc.200601065

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Publishing type：Research paper (international conference proceedings)  

Discrete Element Method (DEM) is widely applied to the numerical simulations of fluidized beds. However, the computational expense increases explosively as the number of particles increases. This issue prevents DEM from applying to real-scale simulations. A model particle method is sometimes used in order to overcome this problem, in which real particles are replaced by larger model particles. When the model particle method is applied, some conditions (e.g., superficial velocity, gas density, gas viscosity, particle density) must be adjusted. Those are referred to as the 'similarity conditions.' In this research the similarity conditions are derived from equations of change through a dimensionless analysis. Bubble motion is compared between the model particle cases and the real particle case to validate the proposed similarity conditions. When the diameter of the model particle is less than 7 times the real particle, the model particle case can predict the bubble motion in the real particle case.

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Language：Japanese   Publisher：The Visualization Society of Japan  

In this research, we carried out the evaluation of the measurement accuracy for an in-line stereoscopi PIV system with a single camera. Conventional stereoscopic PIV systems use two or more cameras, thus a complex adjustment of camera settings is necessary. We developed a simple stereoscopic PIV systel composed of a single camera, mirrors and a half-mirror. This system is applied to in-line stereogrammeti method, which requires that the two cameras have the same optical axis. In this developed system, howeve one camera is replaced with the mirrors, and a double particle image is separated using the half-mirror.

DOI： 10.3154/jvs.25.Supplement2_195

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Language：Japanese   Publisher：The Visualization Society of Japan  

MRI (magnetic resonance imaging) measurement was performed for a horizontally vibrated granular bed of binary mixtures in a liquid. Larger particles tended to rise through the central region. The size ratio of larger to smaller particles affected the segregation phenomena. The experimental results were compared with results of a DEM simulation. The calculated results agreed qualitatively well with the experimental results.

DOI： 10.3154/jvs.25.Supplement2_261

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Language：Japanese   Publisher：The Visualization Society of Japan  

This paper describes the measurement of particle behavior inside a spouted bed by using MRI. We measured the particle velocity distribution in the annulus region in a three-dimensional cylindrical spouted bed. The tagging method and the phase method, which are the velocity measurement technique of MRI, are employed to measure the particle velocity distribution. A stagnation region near the corner of the vessel is clearly visualized by the tagging method. A plug-like motion of particles in the upper part is also visualized. The velocity distribution obtained by the phase method is integrated to calculate particle flow rates at each height.

DOI： 10.3154/jvs.25.Supplement2_279

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：VSP BV  

The aerodynamics of particles and heat transfer of gas-to-particles in a two-dimensional spouted bed (2DSB) with draft plates are investigated by the discrete element method (DEM). The physical properties of the particles are similar to those of shelled corn. The calculated minimum spouting velocity and pressure drop agree well with the empirical correlations proposed by Kudra et al. The particle circulation rate increases when the friction coefficient decreases or the separation height increases. The draft plates can reduce the minimum spouting velocity and pressure drop. They also increase the maximum spoutable bed height. The effect of taking out the draft plates on the spouting phenomenon is investigated. The mixing of a 2DSB without draft plates of 10 000 particles is better than that of 26 000 particles. In our simulation, the gas-to-particle heat transfer is investigated. The Ranz-Marshall correlation and the correlation of Sartori et al. are applicable in the spout region and the downcomer region, respectively. The gas-to-particle heat transfer occurs mainly in the central or spout region, as reported by Freitas and Freire.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The aerodynamics of particles and gas flow in a two-dimensional spouted bed (2DSB) with draft plates is investigated with the aid of the discrete element method. The geometry of the 2DSB with draft plates is set as close as possible to the experimental apparatus of Kudra [1] and Kalwar [2]. The physical properties of the coarse particles are similar to those of shelled corn. The calculated minimum spouting velocity and pressure drop agree well with the correlations of Kudra [1] and Kalwar [2]. In the spout region, the particle vertical velocities are found to decrease as the height increases. The fluid velocity in the downcomer region decreases as the superficial gas velocity increases. The particle circulation rate increases when the friction coefficient decreases or the separation height increases. At the minimum spouting velocity, the bed height does not affect the particle circulation rate in the 2DSB with draft plates. ne draft plates not only reduce the minimum spouting velocity and pressure drop but also increase the maximum spoutable bed height. The effect of taking out the draft plates on the spouting phenomenon is investigated and the effect of putting in a deflector on the possible breakage of the particles is also estimated.

DOI： 10.1002/ceat.200401918

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This paper describes the measurement of particle behavior of inner structure by using MRI. Another way to measure inner structure is X-ray, but it is harmful to human body and can not measure velocity. We measured the radial and axial segregation of mixture of different size particle in a rotating cylinder. The effects of cylinder shape and particle size on segregation phenomena were studied. Furthermore, the particle velocity distribution was measured by the tagging method.

DOI： 10.1299/jsmemecjo.2004.2.0_221

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Noise reduction and vibration control at high speed railway are required to improve the interior noise characteristics of aluminum car body system, which is used shinkansen train and express train. However, it becomes difficult to maintain the vibration control of one link mechanism between the car body and the car bogie. In this paper, to improve the damping performances of one link mechanism, we have proposed a new type noise reduction link mechanism using granular materials. Factors which affect the damping performances are examined through a numerical simulation study. The present noise reduction link mechanism is studied via examining damping performance with granular mass effect and friction effect. Finally, in the numerical simulation by using the discrete element method (DEM), new type noise reduction link mechanism is improved by max. 4.6dB in comparison with the conventional one.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The solids motion in a gas-solid fluidized bed was investigated via discrete particle simulation. The motion of individual particles in a uniform particle system and a binary particle system was monitored by the solution of the Newton's second law of motion. The force acting on each particle consists of the contact force between particles and the force exerted by the surrounding fluid. The contact force is modeled by using the analogy of spring, dash-pot and friction slider. The flow field of gas was predicted by the Navier-Stokes equation. The solids distribution is non-uniform in the bed, which is very diluted near the center but high near the wall. It was also found that there is a single solids circulation cell in the fluidized bed with ascending at the center and descending near the wall. This finding agrees with the experimental results obtained by Moslemian. The effects of the operating conditions, such as superficial gas velocity, particle size, and column size on the solids movement, were investigated. In the fluidized bed containing uniform particles better solids mixing was found in the larger bed containing smaller size particles and operated at higher superficial gas velocity. In the system containing binary particles, it was shown that under suitable conditions the particles in a fluidized bed could be. made mixable or non-mixable depending on the ratios of particle sizes and densities. Better mixing of binary particles was found in the system containing particles with less different densities and closer sizes. These results were found to follow the. mixing and segregation criteria obtained experimentally by Tanaka et al. (C) 2003 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0009-2509(02)00625-5

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

The effect of ambient air temperature on the minimum fluidization velocity U-mf of glass beads is investigated by Distinct Element Method (DEM). Under different ambient air temperatures, the pressure drop curves are calculated by DEM to determine U-mf. The mean kinetic energy E of particles is defined to judge whether the particles move or not. The fluidization characteristics of fluidized bed are investigated in details. The calculated Umf is compared with empirical data. The different behavior of Geldart B and D particles against temperature is reproduced numerically. Umf decreases with increasing ambient temperature for Geldart B particles, while it increases for Geldart D particles.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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.

DOI： 10.1299/jsmemecjo.2002.3.0_307

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Mechanical Engineers  

The effect of pulsating gas injection on the flow pattern was studied numerically. Discrete element method was applied to the solid-phase calculation. To examine the effect of particle condition, two case of solid particles were considered: one is Group B particles in Geldart's classification and the other is Group D particles. The multiple bubbling state without pulsation was chosen as the basis gas-flow condition. In order to characterize quantitatively the effect of the gas pulsation on the flow pattern, we analyzed power spectra of the distributions of void fraction and solid velocity. The results of the present simulations suggests that the gas pulsation largely modifies the solid flow patterns in a low frequency range. Especially in the case of Group B particles, the pattern of bubbles tends to be ordered by applying the gas pulsation.

DOI： 10.1299/kikaib.68.115

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In this study, a discrete particle model for flows of Group-A particles in Geldert's classification is investigated. The corresponding experiments are made for validation of the numerical predictions. The effects of lubrication and adhesion between particles on the fluidization behavior is examined.

DOI： 10.1299/jsmemecjo.II.01.1.0_241

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We have studied numerically and empirically about density waves in standpipe flows. In our past studies, however, the calculated plug velocity was different from the measured velocity. In the present study, we measured the pressure loss property and modified the fluid drag coefficient. By applying the modified drag coefficient to our calculation model, the calculated plug velocity agreed well with the measured velocity.

DOI： 10.1299/jsmemecjo.II.01.1.0_243

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Flows in a spouted bed in a cylinder with a tapered bottom were simulated numerically. To reduce the computational load, a quasi-three-dimensional numerical simulation method for axisymmetric gas-solid flows was proposed. Fluid motion was calculated two-dimensionally by solving the locally averaged equations written in cylindrical coordinates, in which the circumferential components were neglected assuming the axisymmetry. Particle motion was calculated three-dimensionally and was traced discretely by solving Newton's equation of motion for each particle. The discrete element method (DEM) was employed to model the interaction between particles. The typical flow pattern of the spouted bed was obtained in the present calculation, i.e., a stable spout, fountain and annulus were obtained. The calculation was made for the same geometry as the experiment by Roy et al. [D. Roy, F. Larachi, R. Legros, J. Chaouki, Can. J. Chem. Eng. 72 (1994) 945-952]. The calculated spout diameter agreed quantitatively well with their experimental result. The calculated distributions of the vertical component of the particle velocity in the spout, the fountain and the annulus were compared with the experiments by He et al. [Y.-L. He, S.-Z. Qin, C.J. Lim, J.R. Grace, Can. J. Chem. Eng. 72 (1994) 561-568], in which smaller particles were used. The calculated velocity profiles agreed qualitatively well with the experimental results in spite of the difference in the particle diameter. (C) 2000 Elsevier Science S.A. All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

Dense gas-solid flows in a vertical pipe are important relating to many industrial applications; for example, standpipe flows in circulating fluidized beds or vertical plug flows in pneumatic conveying systems. In such flows, particles do not disperse uniformly in the pipes but form clusters, or generate density waves. Experimental and numerical studies have been performed for small-scale standpipe flows, and a power law have been found in power spectra of the density waves. In the present work, we analyzed the density wave in an industrial-scale vertical pipe, and found the similar power law in it although the value of the exponent was different from that of the previous works for small-scale systems. We also performed a numerical simulation based on the discrete element method (DEM) coupled with CFD. The calculated value of the exponent agreed quantitatively with that in the corresponding experiment. The effect of the gas velocity on flow structure was also investigated.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PROGRESS THEORETICAL PHYSICS PUBLICATION OFFICE  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A distinct element model is used to study the hydrodynamics of large-particle fluidized beds. The computed bubble rise velocity, voidage variations, averaged particle/particulate and fluid velocities are compared with the other continuum theory based on two fluid model. Based on the averaged particle/particulate velocities in a grid cell, deformation of the particle layers predicted by the two fluid model and the distinct element method are also compared. The predicted characteristics of bubble formation, motion, and eruption at the bed surface are in good qualitative agreement with the experimental observations. The quantitative differences in predicting the above parameters along with the advantages and limitations of two approaches for the case of a single isolated bubble rising in a two-dimensional fluidized bed are discussed. (C) 1998 Elsevier Science S.A, All rights reserved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

An Eulerian/Lagrangian-type numerical simulation was performed on a two-dimensional fluidized bed in which the particle motion is restricted by parallel front and rear walls. Particle motion was calculated using Newton's equation of motion, and the contact forces were modeled by the discrete element method. The locally averaged equations were solved to calculate the fluid motion, taking into account the interaction between fluid and particles. Two kinds of models were used regarding the calculation of the particle motion: a two-dimensional model and a three-dimensional model. Results for both cases were compared with each other and the effect of the walls on the particle motion is discussed. Cases where partition walls are set up artificially in the bed are also calculated. (C) 1998 Elsevier Science S.A. All rights reserved.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SOC IMAGING SCIENCE & TECHNOLOGY  

It is desired that toners and carriers are mixed well and charged appropriately in the two-component developers of electrophotography. Further these two kinds of particles should be transported to the latent image on the photoconductive drum steadily and at a proper rate. Screw feeders are often used for this process because it is suitable for dealing with mixing, charging and transporting simultaneously. Unfortunately, it is very difficult to know experimentally details of dynamic behavior of particles affected by complicated geometric conditions in the developers unit. As a method for calculating particle motion, DEM (Discrete Element Method) has been attracting a great attention in various fields related to powder and particles. In DEM motion of individual particles is calculated by using the Newton's equations of motion. DEM was applied in this work to study motion of carriers in a screw feeder. The properties concerning mixing and transporting particles were analyzed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA LAUSANNE  

Numerical simulation, in which the motion of individual particles was calculated, was performed of a two-dimensional gas-fluidized bed. Contact forces between particles are modeled by Cundall's Distinct Element Method (P.A. Cundall and O.D.L. Strack, Geotechnique, 29 (1979) 47), which expresses the forces with the use of a spring, dash-pot and friction slider. The gas was assumed to be inviscid and its flow was solved simultaneously with the motion of particles, taking into account the interaction between particles and gas. The simulation gives realistic pictures of particle motion. Formation of bubbles and slugs and the process of particle mixing were observed to occur in the same way as in experiments. The calculated pressure fluctuations compared well with measurements.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

The flow patterns in two-dimensional gas fluidized bed were simulated numerically by the Distinct Element Method. Gas is issued through the entire width of the base with uniform velocity. Several flow patterns, such as slugging and bubbling, are observed in the results. As the gas flow rate increases, the flow pattern changes from slugging to bubbling. It is confirmed that particle mixing is promoted by bubbling. The flow pattern of bubbling is irregular in comparison with the case of gas injection through a central nozzle which was simulated in our previous study.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：FINE PARTICLE SOC  

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

It is difficult to apply optical techniques to the velocity measurement of the fluid-particle flows, especially when the volume fraction of the particle becomes high. In the present paper, the NMR (Nuclear Magnetic Resonance) measurement is applied to dense liquid-solid flows. The velocity distribution of the liquid-solid flow is measured non-invasively by the phase method. It is verified that the velocity distribution of the laminar and the turbulent flow for the single phase flow agrees with the theoretical solution or the empirical correlation. The velocity distribution of the turbulent liquid-solid flow is successfully measured and compared with the wall law.

DOI： 10.1299/jsmemecjo.2009.7.0_69

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

The behavior of flows containing dense particles is very complex. Due to the particle-particle collision effect and hydrodynamic effect caused by the fluid existing in-between particles, particles make spontaneous structures. Flow characteristics are heavily depending on these internal structures and it is important to know why and what sort of structure is formed in the flow field. In the present study, internal flow structures of the flow containing dense particles are calculated by coupling Full-resolved DNS and DEM (Discrete Element Method).

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

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In recent years, many researchers study on characteristic concentrations of particles in turbulent flows. However, it is difficult to observe experimentally interactions between the particles and turbulent vortices because of strong nonlinearity of turbulence. In the present study, we focus on the elementary step of an interaction between single vortex tube and a solid particle in a solid-liquid two-phase flow. Burgers vortex is chosen as single vortex tube. Burgers vortex is the simplest model of turbulence.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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Effects of various gas inflow conditions in fluidized beds are studied by analyzing bubble sizes and motions. Gas inflow conditions are changed by conditions of gas distributor and gas pulsation. DEM (Discrete Element Method) is employed to calculate the motion of individual particle. Bubble sizes and motions can be controlled by the void fraction of distributor. In this study, bubble sizes and motions are hardly influenced by the pressure drop of the distributor. Bubble sizes can be controlled by the gas pulsation in particular frequency range.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Lattice Boltzmann Method (LBM) is applied to the numerical simulation of flows through face-centered cubic arrays of spheres. We examine the effect of space resolution and flow direction on the fluid drag of spheres. It is found that much higher space resolution is required to predict the fluid drag than the flow around isorated sphere. In addition, simulations are made for a sphere moving in a stationary fluid to study the effect of moving boundary.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is widely accepted that DEM (Discrete Element Mehod) simulation reproduct flow phenomena in fluidized beds well. This method inherently has limitation to apply to real large scale systems. To reduce computational load, a numerical model using similarity is proposed in which the motion of a large number of small particles is simulated by a small number of large model particles. This study aims to give a criterion for the limitation on the diameter of model particles. Limitation on diameter of model particle is investigated using particle convective energy and particle displacement.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A model for the fluid drag force in a gas fluidized bed with size distribution is proposed in the present study. The proposed model is applied to a discrete particle simulation of gas fluidized bed of binary mixture. An experimental study is also performed for the model validation. For the validation, we compared numerical results with experimental data at pressure drop property and segregation phenomenon of the bed.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

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In the present study effects of pressure drop of a distributor on particle motion in fluidized beds are studied empirically and numerically. The Discrete Element Method (DEM) is employed to calculate the motion of individual particle. The predicted pressure drop of the disributor reguired to achieve uniform flows agreed well with previous empirical findings.

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We have studied motion of plugs in a standpipe by a DEM simulation. We developed a simpler one-dimensional granular flow model than DEM from the detailed information about the plug motion predicted by the DEM simulation. It is shown that the proposed flow model can express coalescence and brakeup of plugs qualitatively. It can reduce drastically the computational load.

CiNii Books

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Language：Japanese   Publisher：石川島播磨重工業技術本部管理部  

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

An Eulerian/Lagrangian type numerical simulation was performed for two dimensional fluidized beds in a rectangular vessel. The motion of individual particles was calculated two dimensionally by solving the Newton's equations of motion. This method inherently has the limitation : the number of particles. To reduce the number of particles, a numerical model using similarity is proposed. The motion of small particle is calculated by large virtual particles. The distribution of fluid velocity and the normal stress between particles was analyzed to investigate the flow structure of the particle bed in detail.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A model of granular flows in the lattice-Boltzmann framework is proposed. The most significant difference of the motion of granular flows from that of gas molecules which characterize the granular flow is the dissipation of kinetic energy. In the present model, the kinetic-energy dissipation is expressed in terms of the equilibrium distribution function in the BGK model. The present model is applied to the granular clustering process. The result is validated by comparing the corresponding results with those by deterministic simulations.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

We have studied numerically and empirically about density waves in standpipe flows. In our past studies, however, the calculated plug velocity was different from the mesured velocity. In the present study, we measured the pressure loss property and modified the fluid drag coefficient. By applying the modified drag coefficient to our calculation model, the calculated plug velocity agreed well with the measured velocity.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

It is known that the fluidization behaviour in eas-solid fluidized beds depends on the particle diameter and density. In the present study, we investigated a discrete particle model for flows of Geldart's Group-A particles, which have relatively small diameter and are easy to be fluidized, in the fluidized bed. We studied the effects of lubrication and adhesion between particles on the fluidization behaviour.

CiNii Books

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Language：Japanese  

We have studied numerically and empirically about density waves in standpipe flows. In our past studies, however, the calculated plug velocity was different from the measured velocity. In the present study, we measured the pressure loss property to modify the fluid drag coefficient on the particle assembly. By applying the modified drag coefficient to our numerical model, the calculated plug velocity agreed well with the measured velocity.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

A numerical simulation of granular flow between two concentric cylinders, of which inner cylinder rotating and outer cylinder at rest, is performed by the discrete element method (DEM). Effects of particle parameters, for example, coefficient of restitution, coefficient of friction, on the granular flows are studied. In a case of no energy disipation, which corresponds to a molecular model, Taylor voltex appears. 0n the other hand, in cases of energy disipation with gravity, voltex motions are observed but their charcteristic feature is different from Taylor voltex. It is observed that the direction of the voltex motion depens on the rotation speed of the inner cylinder.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Discrete element simulations are performed to investigate the effect of pulsating gas velocity on the bed expansion and the bubble formation in two-dimensional pulsating fluidized beds. Simulations are performed using not only 2D model but also fully-3D model. The bed expansion in the case of pulsating gas injection becomes larger than that without pulsation. In the low pulsation frequency range, the bed expansion and the bubble diameter take the maximum value. Their values are independent of the pulsation frequency for f_p >4.0Hz. There is no significant difference between the macroscopic flow pattern obtained from 2D and 3D model.

CiNii Books

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Numerical analyses of incompressive flows around a solid cylinder approaching to a solid wall are performed to examine the applicability of Moving Particle Semi-implicit (MPS) method to studying the influence of fluid motion on interaction between solid bodies. In this study, fluid flow and motion of the solid cylinder are calculated by using MPS method, which is a kind of particle methods. The results are compared with those of BFC numerical simulations. It is found that the predicted particle approaching velocities are slightly larger than those of BFC numerical simulations. The effect of size of the particle element are also studied.

CiNii Books

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Language：Japanese  

The present paper describes about a discrete particle simulation of pulsating fluidized beds. We investigated numerically the effect of pulsation of the gas velocity on the particle motion. When the pulsation frequency was low, particles moved violently up-and-down synchronizing with the pulsation of the gas velocity. When the pulsation frequency was high enough, the particle motion became independent of the frequency. In this saturated state, the bed expansion from the non-pulsating condition was not very notable. However, it was found that the mean kinetic energy of particles increased significantly. It was verified that pulsation of the gas velocity enhances the particles' convective motion.

CiNii Books

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Language：Japanese  

CiNii Books

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Venue：Leipzig (Germany)  

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Venue：Tampa Bay (USA)  

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Venue：Tampa Bay (USA)  

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Venue：Sapporo  

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Venue：Sapporo  

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Venue：Sapporo  

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Venue：Orlando (USA)  

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Venue：Orlando (USA)  

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Venue：Orlando (USA)  

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Venue：Orlando (USA)  

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Venue：Orlando (USA)  

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Venue：Hualien (Taiwan)  

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Venue：Aizu  

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Venue：Stuttgart (Germany)  

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Venue：Pisa (Italy)  

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Venue：Yokohama  

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Venue：Yokohama  

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