The Experts below are selected from a list of 19914 Experts worldwide ranked by ideXlab platform
Shu-san Hsiau - One of the best experts on this subject based on the ideXlab platform.
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combined effects of internal friction and bed height on the brazil nut problem in a shaker
Powder Technology, 2014Co-Authors: Chunchung Liao, Shu-san HsiauAbstract:Abstract We experimentally studied the influence of an intruder's friction coefficient and bed-filling height on the Brazil-nut effect in a quasi-2D vertical vibration granular bed. The motion of intruder was successfully measured using a high-speed camera and the rising time of intruder was determined by using a Particle Tracking Method with the help of image processing technology. The results show that an intruder's friction coefficient and filling bed height play significant roles in the rise dynamics. The results also show that the rise time increases when the intruder's friction coefficient increases, which is reduced when the filling bed height decreases. Penetration length and friction drag force were also determined in this study. The penetration length was reduced and the friction drag force was enhanced with the increase of an intruder's friction coefficient and bed height. Additionally, the variation between the rise times of the smooth and rough intruders was not significant with the lower bed-filling heights.
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experimental study on the effect of surface roughness of the intruder on the brazil nut problem in a vertically vibrated bed
Physical Review E, 2012Co-Authors: Chunchung Liao, Shu-san HsiauAbstract:This study experimentally investigates the influence of intruder surface roughness in the Brazil nut effect in a quasi-two-dimensional vertical vibration granular bed. The intruder dynamics are determined using a Particle-Tracking Method. The results show that surface roughness has a crucial role in the intruder rise dynamics; a rougher intruder has more difficulty rising in the bed because of higher kinetic energy dissipation. This study determined that penetration length and drag length are reduced and drag is enhanced as intruder surface roughness increases. The exponential decay of the penetration length with vibration frequency is shown. The results also show that at higher dimensionless vibration acceleration and lower vibration frequency the variation in rise time between smooth and rough intruders is negligible.
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experimental study on the influence of bed height on convection cell formation
Experiments in Fluids, 2011Co-Authors: Shu-san Hsiau, Chunchung Liao, Poyen Sheng, Shihchang TaiAbstract:In this study, we have investigated experimentally the convection phenomenon of granular matter in a vertical shaker device. The motions of the granular materials were recorded by a high-speed camera. Image processing technology and a Particle Tracking Method were employed to measure the convection strength, convection size, and granular temperature. The results show that the initial bed height, dimensionless vibrating acceleration, and vibrating frequency have significant influence on the convection mechanism. An interesting finding that occurs with increasing the bed height is the existence of two peaks and one low convection strength value which occurs due to the growth of the solid-like region. We also find that the two peak and one low values become greater when higher dimensionless vibrating acceleration is applied to the granular bed.
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Granular convection cells in a vertical shaker
Powder Technology, 2000Co-Authors: Shu-san Hsiau, C.h ChenAbstract:Granular materials exhibit convective motions in a confined box under external vibration. Particles move upward in the center and flow downward along the side walls. This paper experimentally studies the phenomena of convection cells in a two-dimensional box with 3-mm glass beads under different vibration intensities. Using image processing technology and Particle Tracking Method, the velocity fields of the convective granular beds were measured and analyzed at different vibration conditions. The vertical and horizontal velocity profiles at different locations were investigated. The convection cell centers could be determined from the velocity profiles. The convection flow rate was calculated and had a power law dependence on the amplitude of the vibration velocity.
Felipe P J De Barros - One of the best experts on this subject based on the ideXlab platform.
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par2 parallel random walk Particle Tracking Method for solute transport in porous media
Computer Physics Communications, 2019Co-Authors: Calogero B Rizzo, Aiichiro Nakano, Felipe P J De BarrosAbstract:Abstract Computational modeling of solute migration in groundwater systems is a fundamental component in water resources management and risk analysis. Therefore, it is imperative to have fast and reliable computational tools to simulate solute transport in groundwater systems. In this work we present PAR 2 , a GPU-accelerated solute transport simulator based on the Random Walk Particle Tracking (RWPT) technique, a Lagrangian Method particularly suited for parallelization. PAR 2 is able to run on any computing platform equipped with an NVIDIA GPU, such as common desktops and High-Performance Computing (HPC) nodes. The program is developed in C++/CUDA. In our illustration, groundwater flow is simulated on a structured grid using MODFLOW, which can be linked to PAR 2 using the LMT package. Simulation parameters can be defined through a convenient YAML configuration file. Additionally, we propose an analytical treatment of the dispersion tensor that allows the RWPT to be effectively implemented using GPU parallelization. The speedup gained with the parallelization drastically reduces the total simulation time, allowing the application of computationally expensive algorithms (e.g., Monte-Carlo simulation) on large-scale stochastic hydro-systems. Program summary Program Title: PAR 2 . Program Files doi: http://dx.doi.org/10.17632/4pkhgx8wcb.1 Licensing provisions: GPLv3 Programming language: C++/CUDA Nature of problem: GPU-accelerated simulation of solute transport in saturated porous media. Solution Method: Implementation of the Particle Tracking Method, a fully Lagrangian approach to solve the advection–dispersion equations.
David Y H Pui - One of the best experts on this subject based on the ideXlab platform.
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predicting collision efficiencies of colloidal nanoParticles in single spherical and fibrous collectors using an individual Particle Tracking Method
Separation and Purification Technology, 2019Co-Authors: Handol Lee, Seong Chan Kim, Sheng Chieh Chen, Doris Segets, David Y H PuiAbstract:Abstract We investigate the deposition of colloids onto granular and fibrous collectors by computational fluid dynamics (CFD) simulations. In particular the collision efficiency under unfavorable conditions, i.e., like-charged surfaces, was in focus. Particle trajectories were analyzed in a Lagrangian reference frame using a discrete phase model (DPM). By user-defined functions (UDFs) we incorporated interception as important deposition mechanism and calculated interaction energies between Particle and collector surfaces utilizing the extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory. Adhesive and hydrodynamic torques acting on deposited Particles were compared through the developed UDFs to consider Particle detachment. Within each DPM process, all abovementioned calculations on every Particle are performed continuously, allowing to understand Particle deposition under different physico-chemical conditions. Simulated data on collision efficiencies for the granular collector were in good agreement with theory and experiments. Simulations for the fibrous collector showed that with increasing fluid velocity the hydrodynamic torque acting on Particles attached to smaller fibers was increased. This enhanced the detachment and significantly lowered the collision efficiency, especially for larger Particles. In conclusion, the developed CFD Methods for predicting the collision efficiency on granular and fibrous collectors provide a powerful tool for examining the deposition behaviors of colloidal Particles in porous media.
Diogo Bolster - One of the best experts on this subject based on the ideXlab platform.
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elimination of the reaction rate scale effect application of the lagrangian reactive Particle Tracking Method to simulate mixing limited field scale biodegradation at the schoolcraft mi usa site
Water Resources Research, 2017Co-Authors: Dong Ding, David A Benson, Daniel Fernandezgarcia, Christopher V Henri, David W Hyndman, Mantha S Phanikumar, Diogo BolsterAbstract:Measured (or empirically fitted) reaction rates at groundwater remediation sites are typically much lower than those found in the same material at the batch- or laboratory-scale. The reduced rates are commonly attributed to poorer mixing at the larger scales. A variety of Methods have been proposed to account for this scaling effect in reactive transport. In this study, we use the Lagrangian Particle Tracking and reaction (PTR) Method to simulate a field bioremediation experiment at the Schoolcraft, Michigan site. A denitrifying bacterium, Pseudomonas Stutzeri strain KC (KC), was injected to the aquifer, along with sufficient substrate, to degrade the contaminant, Carbon Tetrachloride (CT), under anaerobic conditions. The PTR Method simulates chemical reactions through probabilistic rules of Particle collisions, interactions, and transformations to address the scale effect (lower apparent reaction rates for each level of upscaling, from batch- to column- to field-scale). In contrast to a prior Eulerian reaction model, the PTR Method is able to match the field-scale experiment using the rate coefficients obtained from batch experiments.
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the impact of inertial effects on solute dispersion in a channel with periodically varying aperture
Physics of Fluids, 2012Co-Authors: J Bouquain, Diogo Bolster, Yves Meheust, Philippe DavyAbstract:We investigate solute transport in channels with a periodically varying aperture, when the flow is still laminar but sufficiently fast for inertial effects to be non-negligible. The flow field is computed for a two-dimensional setup using a finite element analysis, while transport is modeled using a random walk Particle Tracking Method. Recirculation zones are observed when the aspect ratio of the unit cell and the relative aperture fluctuations are sufficiently large; under non-Stokes flow conditions, the flow in non-reversible, which is clearly noticeable by the horizontal asymmetry in the recirculation zones. After characterizing the size and position of the recirculation zones as a function of the geometry and Reynolds number, we investigate the corresponding behavior of the longitudinal effective diffusion coefficient. We characterize its dependence on the molecular diffusion coefficient Dm, the Peclet number, the Reynolds number, and the geometry. The proposed relation is a generalization of the well-known Taylor-Aris relationship relating the longitudinal dispersion coefficient to Dm and the Peclet number for a channel of constant aperture at sufficiently low Reynolds number. Inertial effects impact the exponent of the Peclet number in this relationship; the exponent is controlled by the relative amplitude of aperture fluctuations. For the range of parameters investigated, the measured dispersion coefficient always exceeds that corresponding to the parallel plate geometry under Stokes conditions; in other words, boundary fluctuations always result in increased dispersion. The transient approach to the asymptotic regime is also studied and characterized quantitatively. We show that the measured characteristic time to attain asymptotic conditions is controlled by two competing effects: (i) the trapping of Particles in the near-immobile zone and, (ii) the enhanced mixing in the central zone where most of the flow takes place (mainstream), due to its thinning.
Deoggyu Seo - One of the best experts on this subject based on the ideXlab platform.
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a new Method to measure the polymerization shrinkage kinetics of composites using a Particle Tracking Method with computer vision
Dental Materials, 2012Co-Authors: Inbog Lee, Sunhong Min, Deoggyu SeoAbstract:Abstract Objectives The aim of this study was to develop a new Method to measure the polymerization shrinkage of light cured composites and to evaluate the overall utility and significance of the technique. Methods An optical instrument to measure the linear polymerization shrinkage of composites without directly contacting the specimen was developed using a Particle Tracking Method with computer vision. The measurement system consisted of a CCD color video camera, a lens, an image storage device, and image processing and analysis software. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and a flowable Z350) were investigated and compared with the data measured using the “bonded disc Method”. Results The linear shrinkage of the composites was 0.33–1.41%. The shrinkage value was lowest for the silorane-based (P90) composite and highest for the flowable Z350 composite. The estimated volume shrinkages of the materials were comparable to the axial shrinkages measured with the bonded disc Method. Significance The new instrument was able to measure the true linear shrinkage of composites without sensitivity to the specimen geometry and the viscosity of the material. Therefore, this instrument can be used to characterize the shrinkage kinetics for a wide range of commercial and experimental visible-light-cure materials in relation to the composition and chemistry.
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a new Method to measure the linear polymerization shrinkage of composites using a Particle Tracking Method with computer vision
The Journal of Korean Academy of Conservative Dentistry, 2010Co-Authors: Inbog Lee, Sunhong Min, Deoggyu Seo, Sunyoung Kim, Youngchul KwonAbstract:Since the introduction of restorative dental composites, their physical properties have been significantly improved. However, polymerization shrinkage is still a major drawback. Many efforts have been made to develop a low shrinking composite, and silorane-based composites have recently been introduced into the market. In addition, many different Methods have been developed to measure the polymerization shrinkage. In this study, we developed a new Method to measure the linear polymerization shrinkage of composites without direct contact to a specimen using a Particle Tracking Method with computer vision. The shrinkage kinetics of a commercial silorane-based composite (P90) and two conventional methacrylate-based composites (Z250 and Z350) were investigated and compared. The results were as follows: 1. The linear shrinkage of composites was 0.33-1.41%. Shrinkage was lowest for the silorane-based (P90) composite, and highest for the flowable Z350 composite. 2. The new instrument was able to measure the true linear shrinkage of composites in real time without sensitivity to the specimen preparation and geometry. [J Kor Acad Cons Dent 35(3):180-187, 2010]
