Direct calculation of inter-particle distance in suspension by image processing

Elsevier 2018 Powder technology Vol.330 No.-

<P><B>Abstract</B></P> <P>With the difficulties to measure inter-particle distance in a suspension, the theoretical value under the several assumptions has been used. In this study, an image processing method for directly calculating inter-particle distances in a suspension was developed. This method enables inter-particle distances to be calculated regardless of the particle size, distribution, and morphology. A surface of suspension composed of particles and wax-polymeric binder was polished with acetone to expose the particles from the binder. The particles measured by scanning electron microscope were distinguished from the binder through the developed image processing method based on the intensity difference between the particles and binder. The inter-particle distances between the randomly selected particles and neighboring particles were calculated using the centroids and boundaries obtained by image processing. To determine the inter-particle distance as a representative value, a Monte Carlo method was employed. The inter-particle variation was defined to determine the iteration number for the Monte Carlo method. Finally, the inter-particle distances for the particle volume fraction of 40 and 50 vol% were obtained by the developed method. In addition, this developed method is available to describe the physical phenomenon such as a powder-binder separation and critical solid loading.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Image processing method directly calculates inter-particle distance of suspension. </LI> <LI> This direct measurement method is more reliable than previous theoretical models. </LI> <LI> Obtained inter-particle distances are less than mean particle size and reasonable. </LI> <LI> The increase of powder volume fraction leads to the decrease of inter-particle distance. </LI> <LI> The inter-particle distance calculation method is applicable in various industries. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

향상된 경계층 추적기법을 이용한 다중 물질 해석 연구

김기홍,여재익 한국항공우주학회 2011 한국항공우주학회 학술발표회 논문집 Vol.2011 No.11

다중 물질의 변화를 해석하기 위하여 필수적인 경계면 추적에 대하여 hydro particle level set method 와 같은 경계층 추적기법이 폭넓게 사용되고 있다. Level set 기법은 결합, 쪼개짐과 같은 위상의 변화를 정확하게 계산할 수 있지만, 메쉬가 작을 경우 질량이 감소하는 형상이 발생하였다. 이를 해석하기 위하여 Lagrangian 기법 기반의 particle method 를 사용하여 질량 손실을 해결하였다. 하지만 기존의 particle level set 기법은 경계면 주변에 특이점이 있거나, 물체가 나누어지거나 결합될 때의 해석에 어려움이 있어 왔다. 이를 해결하기 위하여 particle method 에서 발생하는 에러를 해결하기 위하여 향상된 particle reseeding 방법을 제안하였으며, 이를 통하여 다중 물질 해석에 관한 여러 현상을 해석하였다. The hybrid particle level set (HPLS) method improves the mass conservation of level set method by using Lagrangian marker particles in under-resolved regions. In the HPLS method, the calculated value of Lagrangian particles is prior to one of level set method and used to rebuild the interface therefore, the accurate and reliable computation of Lagrangian particle method is essential to sustain the exact interface. The particle method preserves exactly the characteristics line, nevertheless is not able to automatically handle merging or deletion of characteristics. So reseeding Lagrangian particles (or regulation) is required to maintain the proper value in the calculation in spite of deleting particles near the interface, losing the characteristic information and moreover, inducing the unintended error or mass loss. Reseeding procedure of the HPLS method is not suitable for compressible flows in which characteristics are often merged or destroyed, and one material is divided into two. In this paper, reseeding procedure of the original HPLS is analyzed and the new reseeding procedure based on the geometrical information and the characteristics line is suggested. Numerical examples in the various phenomena are present to demonstrate our new reseeding procedure in HPLS method.

Solid Particle Simulation with a New Particle Interaction

Kyung Sung Kim 대한전자공학회 2021 IEIE Transactions on Smart Processing & Computing Vol.10 No.5

A particle method is a state-of-the-art method in computational fluid dynamics. The specialty of the particle method is tracking each particle that carries its own physical quantities, such as velocity, pressure, and position. Therefore, the large deformation of a free surface can be simulated. In this paper, the concept of the fully Lagrangian approach is extended in its applicability to the solid particle with new particle interaction models, which are the friction and drag models. The newly developed particle method with the new particle interaction models simulated mobile sea-bed behavior under very violent waves due to the broken dam problem. The numerical results were compared to corresponding experimental results for validation. The validated particle method demonstrated the mobile sea-bed behavior with various densities of soil particles. Furthermore, solid-particle interaction model results were also compared with those of fluid models to show the difference and to prove the implementation.

Simultaneous control of size and surface functionality of silica particle via growing method

Moon, Seongjun,Lee, Kyung Jin Elsevier 2017 Advanced powder technology Vol.28 No.11

<P><B>Abstract</B></P> <P>Although silane treatment has been studied asa simple and powerful tool to modify the surface of silica particle, there are still several difficulties in terms of controlling surface functionality and size of nanoparticles. Here we develop a growing method to overcome above drawback. The method was processed by continuously injecting precursor using syringe pump. According to the continuous injection, the concentration of precursors in media are properly controlled, and then the continuous injection of precursor promotes the growth of silica particles. When the functional silanes (silane coupling agents) are used, the method can control the amount of surficial functional groups on the silica particle, and can adjust diameter of the particle simultaneously. Furthermore, well-controlled functional silica particles made by growing method are used for catalytic reaction, Knoevenagel reaction, asa solid state catalyst.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Controlling amount of surface functional groups and size of particles simultaneously. </LI> <LI> Efficient particle growth method using continuous injection of precursors. </LI> <LI> Increasing the amount of organic functional groups on the particles. </LI> <LI> Controlling quantity of the functional group. </LI> <LI> Enhanced catalytic activity maintaining their hydrophilic property. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Growing method for particle growth and surface modification of silica particle has been developed through continuously injecting precursors and modified silane in order to control amount of surface functionality. The growing method provide a growth of seed silica particle and silane-treated surface simultaneously. The amount of amine functional groups on silica particle can be controlled for catalytic reaction.</P> <P>[DISPLAY OMISSION]</P>

Analysis of Magnetic Particle Agglomeration Structure and Interaction Forces Between Magnetic Particles

Jia Long,Zixu Miao,Huihuang Chen,Rongdong Deng,Weiran Zuo,Bao Guo,Jiangang Ku 한국자기학회 2020 Journal of Magnetics Vol.25 No.1

Chain-like and diamond-shaped magnetic particle agglomeration (MPA) commonly forming in a weak magnetic field are simulated based on the finite element method (FEM), and the effects of particle diameter, magnetic field strength, particle relative magnetic permeability, and particle number in magnetic particle chains (MPCs) and diamond-shaped MPA on the strength of MPA are analysed in detail. The results show that magnetic forces on the centre contact points (CCPs) of MPA are positively correlated with the particle diameter, magnetic field strength, particle relative magnetic permeability, and particle number. In addition, the forces on the CCPs of the MPCs (N=2) have a square relationship with the particle diameter and magnetic field strength and have a power relationship of 1.25 with the particle relative magnetic permeability. The forces on each contact point decrease slowly from the centre to both ends in the MPCs and then rapidly decrease to one value (approximately 0.779 times the forces on the CCPs). As for the diamond-shaped MPA, with the increase in the angle α between the magnetic field and axis of diamond-shaped MPA, the force magnitude of the particle entrained parallelly in the diamond-shaped MPA shows a trend of a “cosine curve” shape and the minimum value is 2109 times that of the entrained particle’s gravity. The angle θ between the direction of the force and the negative X-axis shows a trend of a “sine curve” shape. When α = 25° and 155°, the angle θ of the force on the entrained particle reaches an extreme value, that is, θ = 21.87°. Only if the angle θ reaches 30º can the particle entrained parallelly escape from the diamond-shaped MPA. Thus, the diamond-shaped MPA remains in a stable state and it is difficult to disperse MPA by changing the direction of the magnetic field.

제분방법이 쌀가루의 입자크기에 미치는 영향

금준석,이상효,이현유,김길환,김영인,Kum, Jun-Seok,Lee, Sang-Hyo,Lee, Hyun-Yu,Kim, Kil-Hwan,Kim, Young-In 한국식품과학회 1993 한국식품과학회지 Vol.25 No.5

Two different methods (Sieve shaker, Elzone particle size analyzer) were used to investigate rice flour particle size obtained by various milling method. Results of Elzone particle size analyzer were more effective than Sieve shaker in determining particle size, and the distribution of particle size of rice flours was affected by the type of the milling methods used. A rice flour, prepared in a Pin mill had a particle size range of $60{\sim}500$ mesh, and 30.38% of the sample was in the particle size range $200{\sim}270$ mesh. A rice flour, prepared in a Colloid mill had a particle size range of $40{\sim}500$ mesh and more of flour particles appeared in the range $140{\sim}200$ mesh than any other particle size. A rice flour, prepared in a Micro mill had a particle size range of $140{\sim}500$ mesh, and 41.62% of the sample was in the particle size range over 500 mesh. A rife flour, prepared in a Jet mill had a finer flour particle size was over the particle size range 500 mesh. The finer rice flour gave the highest L value and the lowest a value. The wet-milled flour particles were observed as a cluster of starch granules and the particles of rice flour (dry-milling) were observed as fragment of rice grains. Scanning Electron Photomicrographs revealed that visual differences in structure between milling methods, and similar results with Elzone particle size analyzer method in particle size. Sieve shaker와 Elzone particle size analyzer에 의한 두 가지 방법으로 제분방법에 따른 입자크기를 조사하였다. 제분방법별로 제조한 쌀가루의 입도분포를 측정한 결과 입자크기는 제분방법에 따라 영향을 받았으며 표준망체를 이용한 Sieve shaker 방법보다 Elzone particle size analyzer를 사용한 방법이 정확도가 우수하였다. 입도분포를 측정한 결과 Pin mill의 경우 $200{\sim}270$mesh가 30.38%으로 가장 많았고 $60{\sim}500mesh$의 분포도를 가졌다. Colloid mill은 $140{\sim}200mesh$가 가장 많았으며, $40{\sim}500mesh$의 분포도를 가졌다. Micro mill은 500mesh 이상이 41.62%로 가장 많았고 $140{\sim}500mesh$의 분포도를 보여주었다. Jet mill은 500 mesh 이상의 분포도로 입자크기가 가장 미세하였다. 또한 미세한 입자일수록 L간과 a값이 증가하였다. 쌀가루의 집합체를 살펴본 결과 습식제분은 분리된 쌀가루의 집합체형태로 구성되어 있고 건식제분은 분활된 조직체로 구성되었다. 전자주사현미경은 Elzone particle size analyzer 방법과 같은 입자분포도를 나타내었고 제분방법에 따라 구조의 특성을 보여주었다.

Effects of particle size and adaptation duration on the digestible and metabolizable energy contents and digestibility of various chemical constituents in wheat for finishing pigs determined by the direct or indirect method

Yuanfang Fan,Panpan Guo,Yuyuan Yang,Tian Xia,Ling Liu,Yongxi Ma 아세아·태평양축산학회 2017 Animal Bioscience Vol.30 No.4

Objective: This experiment was conducted as a 3×2×2 factorial design to examine the effects of particle size (mean particle size of 331, 640, or 862 μm), evaluation method (direct vs indirect method) and adaptation duration (7 or 26 days) on the energy content and the apparent total tract digestibility (ATTD) of various chemical components in wheat when fed to finishing pigs. Methods: Forty-two barrows (Duroc×Landrace×Yorkshire) with an initial body weight of 63.0±0.8 kg were individually placed in metabolic cages and randomly allotted to 1 of 7 diets with 6 pigs fed each diet. For the indirect method, the pigs were fed either a corn-soybean meal based basal diet or diets in which 38.94% of the basal diet was substituted by wheat of the different particle sizes. In the direct method, the diets contained 97.34% wheat with the different particle sizes. For both the direct and indirect methods, the pigs were adapted to their diets for either 7 or 26 days. Results: A reduction in particle size linearly increased the digestible energy (DE) and metabolizable energy (ME) contents as well as the ATTD of gross energy, crude protein, organic matter, ether extract (EE) and acid detergent fiber (ADF) (p<0.05), and had a trend to increase the ATTD of dry matter of wheat (p = 0.084). The DE, ME contents, and ATTD of gross energy, crude protein, dry matter and organic matter were higher (p<0.05) when determined by the direct method, but the ATTD of ADF, EE, and neutral detergent fiber were higher when determined by the indirect method (p<0.05). Prolongation of the adaption duration decreased the ATTD of neutral detergent fiber (p<0.05) and had a trend to increase the ATTD of EE (p = 0.061). There were no interactions between particle size and the duration of the adaptation duration. The ATTD of EE in wheat was influenced by a trend of interaction between method and adaptation duration (p = 0.074). The ATTD of ADF and EE in wheat was influenced by an interaction between evaluation method and wheat particle size such that there were linear equations (p<0.01) about ATTD of ADF and EE when determined by the direct method but quadratic equations (p = 0.073 and p = 0.088, respectively) about ATTD of ADF and EE when determined by the indirect method. Conclusion: Decreasing particle size can improve the DE and ME contents of wheat; both of the direct and indirect methods of evaluation are suitable for evaluating the DE and ME contents of wheat with different particle sizes; and an adaptation duration of 7 d is sufficient to evaluate DE and ME contents of wheat in finishing pigs.

Numerical Study on Characteristics of Turbulent two-phase Gas-Particle Flow using Multi-fluid Model

Dongho Min,Kyungbeom Yoon,Heechul Chang,김태국 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.7

The purpose of this research is to study numerically the turbulent gas-particle two-phase flow characteristics using the Eulerian-Eulerian method. A computer code is developed for the numerical study by using the k -ε - kp two-phase turbulent model. The developed code is applied for particle-laden flows in which the particle volume fraction is between n 10−5 and 10−2 for the Stokes numbers smaller than unity. The gas and particle velocities and the particle volume fraction obtained by using this code are in good agreement with those obtained by a commercial code for the gas-particle jet flows within a rectangular enclosure. The gas-particle jet injected into a vertical rectangular 3D enclosure is numerically modeled to study the effect of the Stokes number, the particle volume fraction and the particle Reynolds numbers. The numerical results show that the Stokes number and the particle volume fraction are important parameters in turbulent gas-particle flows. A small Stokes number ( St ≤ 0.07) implies that the particles are nearly at the velocity equilibrium with the gas phase, while a large Stokes number ( St ≥ 0.07) implies that the slip velocity between the gas and particle phase increases and the particle velocity is less affected by the gas phase. A large particle volume fraction ( p α ≥ 0.0001) implies that the effect of the particles on the gas phase momentum increases, while a small particle volume fraction ( p α ≤ 0.0001) implies that the particles would have no or small effect on the gas flow field. For fixed Stokes number and particle volume fraction, an increase of the particle Reynolds number results in a decrease of the slip velocity between the gas and particle velocities.

거친 경계면을 지나는 난류 내 입자의 거동

이혜은(Hea Eun Lee),이창훈(Changhoon Lee) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

Particle motion in turbulence is of major interest in many engineering fields such as coastal and environmental researches. Whereas most boundary conditions for particle motion in turbulence are rough in practice, studies on particle motion still focus on the particle motion over a flat boundary. Since the turbulence generated by rough boundaries is different from that in flat boundaries, detailed study about particle motion along rough boundary is needed. In this study, turbulence over wavy wall is investigated by spectral method. Virtual boundary method proposed by Goldstein et al. (1995) is used to impose no-slip condition at wavy virtual boundary. Also, behavior of particles in turbulence over wavy boundary is investigated by particle tracking. Simulation results are compared with the characteristics of turbulent flow over a wavy wall described in papers for evaluation. Focusing on the effect of wavy boundary on turbulent structures, simulation results from wavy boundaries with different amplitude and wavelength are compared. Streamwise vortices and low-speed streaks, which associate with particle clustering, mainly develop from the upslope region with lengthscale of wavelength in wavy wall cases. Statistics of particle concentration and motion are investigated for inertial particles released in each flow case. In common, particle concentration is high in upslope region and particle velocity and its fluctuation show different characteristics in each flow case and particle inertia.

입자법을 이용한 토사의 대변형 해석법 개발

박성식,이도현,권민호 한국지반공학회 2013 한국지반공학회논문집 Vol.29 No.12

In this study, a particle method without using grid was applied for analysing large deformation problems in soil flowsinstead of using ordinary finite element or finite difference methods. In the particle method, a continuum equationwas discretized by various particle interaction models corresponding to differential operators such as gradient, divergence,and Laplacian. Soil behavior changes from solid to liquid state with increasing water content or external load. TheMohr-Coulomb failure criterion was incorporated into the particle method to analyze such three-dimensional soil behavior. The yielding and hardening behavior of soil before failure was analyzed by treating soil as a viscous liquid. First ofall, a sand column test without confining pressure and strength was carried out and then a self-standing clay columntest with cohesion was carried out. Large deformation from such column tests due to soil yielding or failure was usedfor verifying the developed particle method. The developed particle method was able to simulate the three-dimensionalplastic deformation of soils due to yielding before failure and calculate the variation of normal and shear stresses bothin sand and clay columns.