• 한국컴퓨터그래픽스학회논문지
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• 제25권2호
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• pp.11-18
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• 2019

본 논문에서는 많은 개체와의 충돌 검사를 요구하는 입자 기반 시스템에서 부채꼴 영역의 동적인 변화를 이용하여 효율적으로 충돌 검사를 가속화시킬 수 있는 프레임워크를 제안한다. 입자와 부채꼴 기반의 충돌 영역은 다음 세 가지 조건에 의해 결정된다: 1) 인접 입자의 반경 내에 부채꼴의 위치가 존재하는 경우, 2) 부채꼴 영역 내에 인접 입자의 위치가 존재하는 경우, 3) 부채꼴 영역을 형성하는 두 벡터 사이에 인접 입자가 존재하는 경우. 결과적으로 위 조건들을 모두 만족했을 때 입자와 부채꼴 영역은 충돌되었다고 정의한다. 본 논문에서는 입자의 움직임에 따라 충돌 검사 범위인 부채꼴의 영역을 자동으로 업데이트 한다. 부채꼴 영역의 동적인 변화를 계산하기 위해 입자의 위치와 속도를 기반으로 부채꼴의 방향, 길이, 각도를 조절한다. 최종적으로 계산된 부채꼴 영역 내에 있는 입자들만을 이용하여 충돌 검사를 빠르게 수행한다. 본 연구에서 제안하는 가속화 방법은 트리와 같은 자료구조를 명시적으로 만들지 않고, 닫힌 형태 방정식으로 실행되기 때문에 간단하게 구현되며 모든 결과에서 충돌 검사 성능이 개선되었다.

• 한국전산구조공학회논문집
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• 제36권6호
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• pp.365-370
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• 2023

본 논문에서는 위상최적설계를 위한 입자-구조 충돌 모델을 제시한다. 위상최적설계를 위해서는 민감도 분석이 선행되어야 하며, 민감도 분석이 가능한 새로운 모델이 필요하다. 본 논문에서는 위상최적설계를 위한 민감도 분석을 수행하기 위한 입자-구조 충돌 모델을 제시한다. 이후 이 모델을 이용하여 위상최적설계를 위한 민감도 분석을 수행한다. 제안한 모델의 정확도를 평가하기 위해 먼저 단순화된 1차원 충돌 문제에 적용한다. 이후, 이 모델을 이용하여 위상 최적화를 통해 입자의 최종 위치를 최적화하여 위상 최적화에 대한 이 모델의 적용 가능성을 확인한다. 이러한 결과는 위상 최적화에서 입자-구조 충돌을 고려하는 것이 가능하다는 것을 보여준다.

• 한국유체기계학회 논문집
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• 제15권1호
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• pp.27-35
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• 2012

A numerical simulation for particle collection efficiency in a wire-plate electrostatic precipitator (ESP) has been performed. Method of characteristics and finite differencing method (MOC-FDM) were employed to obtain electric field and space charge density, and lattice boltzmann method (LBM) was used to predict the Electrohydrodynamic (EHD) flow according to the ion convection. Large eddy simulation (LES) was considered for turbulent flow and particle simulation was performed by discrete element method (DEM) which considered field charging, electric force, drag force and wall-collision. One way coupling from FDM to LBM was used with small and low density particle assumption. When the charged particle collided with the collecting plate, particle-wall collision was calculated for re-entertainment effect and the effect of gravity force was considered.

• 상하수도학회지
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• 제12권1호
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• pp.81-87
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• 1998

The possibility of collision of two particles slowly settling one after another in water can be described using the collision efficiency factor in differential sedimentation (${\alpha}_{DS}$). ${\alpha}_{DS}$ was found to be a function of several parameters particle size, particle size ratio, Hamaker constant, density of liquid and particle, gravity acceleration. Previous researches were limited to the case when there is no electric repulsion assuming that the suspension is destabilized. In this paper, ${\alpha}_{DS}$ is calculated for the stabilized condition. The relative trajectory of two particles are calculated including hydrodynamics, attraction and repulsion forces. Ionic strength and surface potential significantly affect the collision possibility of two settling particles. Depending on the surface potential and ionic strength, ${\alpha}_{DS}$ value is divided into three regions; stable, unstable and transition zone. ${\alpha}_{DS}$ increases as the ionic strength increases, and as the surface charge decreases. This result can be used to model both destabilized and stabilized suspension incorporating the collision efficiency factors of the other coagulant mechanisms such as fluid shear and Browian motion.

• 한국분말재료학회지
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• 제21권4호
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• pp.307-312
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• 2014

This study is focused on investigating the relation between the particle size of silver flake powder and mechanical milling parameters. Mechanical milling parameters such as ball size, impeller rotation speed and milling time of the attrition ball-mill were controlled to produce silver flake powder. The particle size of the silver flake powder increased with increasing ball size and impeller rotation speed. The change of the particle size of the silver flake powder with mechanical milling parameters was analyzed based on balls motion in the mill container of the attrition ball-mill. The silver flake particles were formed at the elastic deformation area of the ball due to the collision between balls. The change of the particle size of the silver flake powder with mechanical milling parameters well consists with the change of the collision energy of ball with parameters mentioned above.

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.779-789
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• 2012

In the kinetic theory of dense fluids the many-particle collision bracket integral is given in terms of a classical collision operator defined in the phase space. To find an algorithm to compute the collision bracket integrals, we revisit the eigenvalue problem of the Liouville operator and re-examine the method previously reported [Chem. Phys. 1977, 20, 93]. Then we apply the notion and concept of the eigenfunctions of the Liouville operator and knowledge acquired in the study of the eigenfunctions to cast collision bracket integrals into more convenient and suitable forms for numerical simulations. One of the alternative forms is given in the form of time correlation function. This form, on a further manipulation, assumes a form reminiscent of the Chapman- Enskog collision bracket integrals, but for dense gases and liquids as well as solids. In the dilute gas limit it would give rise precisely to the Chapman-Enskog collision bracket integrals for two-particle collision. The alternative forms obtained are more readily amenable to numerical simulation methods than the collision bracket integrals expressed in terms of a classical collision operator, which requires solution of classical Lippmann-Schwinger integral equations. This way, the aforementioned kinetic theory of dense fluids is made fully accessible by numerical computation/simulation methods, and the transport coefficients thereof are made computationally as accessible as those in the linear response theory.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권1호
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• pp.1-8
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• 2018

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solid-liquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from $1.09g/cm^3$ to $1.75g/cm^3$. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of $1.09g/cm^3$ hit the tongue on the left side, while collision location of particles of $1.75g/cm^3$ is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

• 대기
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• 제22권1호
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• pp.73-85
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• 2012

The collision efficiency data for collision between graupel or hail particles and cloud drops that take into account the differences of particle density are applied to the Takahashi cloud model. The original setting assumes that graupel or hail collision efficiency is the same as that of the cloud drops of the same volume. The Takahashi cloud model is run with the new collision efficiency data and the results are compared with those with the original. As an initial condition, a thermodynamic profile that can initiate strong convection is provided. Three different CCN concentration values and therefore three initial cloud drop spectra are prescribed that represent maritime (CCN concentration = 300 $cm^{-3}$), continental (1000 $cm^{-3}$) and extreme continental (5000 $cm^{-3}$) air masses to examine the aerosol effects on cloud and precipitation development. Increase of CCN concentration causes cloud drop sizes to decrease and cloud drop concentrations to increase. However, the concentration of ice particles decreases with the increase of CCN concentration because small drops are difficult to freeze. These general trends are well captured by both model runs (one with the new collision efficiency data and the other with the original) but there are significant differences: with the new data, the development of cloud and raindrop formation are delayed by (1) decrease of ice collision efficiency, (2) decrease of latent heat from riming process and (3) decrease of ice crystals generated by ice multiplication. These results indicate that the model run with the original collision efficiency data overestimates precipitation rates.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.11-19
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• 2005

First, methods of numerical analysis of gas-particle flows is classified into micro, meso and macro scale approaches based on the concept of multi-scale mechanics. Next, the explanation moves on to discrete particle simulation where motion of individual particles is calculated numerically using the Newtonian equations of motion. The author focuses on the cases where particle-to-particle interaction has significant effects on the phenomena. Concerning the particle-to-particle interaction, two cases are considered: the one is collision-dominated flows and the other is the contact-dominated flows. To treat this interaction mathematically, techniques named DEM(Distinct Element Method) or DSMC (Direct Simulation Monte Carlo) have been developed DEM, which has been developed in the field of soil mechanics, is useful for the contact -dominated flows and DSMC method, developed in molecular gas flows, is for the collision-dominated flows. Combining DEM or DSMC with CFD (computer fluid dynamics), the discrete particle simulation becomes a more practical tool for industrial flows because not only the particle-particle interaction but particle-fluid interaction can be handled. As examples of simulations, various results are shown, such as hopper flows, particle segregation phenomena, particle mixing in a rotating drum, dense phase pneumatic conveying, spouted bed, dense phase fluidized bed, fast circulating fluidized bed and so on.

• 한국도로학회논문집
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• 제19권6호
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• pp.31-36
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• 2017

PURPOSES : The computational fluid dynamics of flow and fine particles in a road were set to determine the insert flow and occurrence characteristics. METHODS : The road extension was 100 m with two lanes. A one-ton truck traveled a 50-m distance. After a noise barrier was installed on one side of the road, the flow and a collision analysis were tested. RESULTS : The flow that occurred was 5 m/s beside the vehicle, and fine particulate was $5.0{\times}10^2{\mu}g/m^3$ after 20 m from the exhaust vent. CONCLUSIONS : After a collision analysis of the fine particulate on the noise barrier to find the most suitable position of the filter panel in height, the bottom 1 m was the most optimum position because 88.1% of the distribution was concentrated there.