• Structural Engineering and Mechanics
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• v.5 no.2
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• pp.209-220
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• 1997

The dynamic equations for an arbitrary cluster comprising rigid spheres or assemblies of spheres (subclusters) encountered in granular-type systems are considered. The system is treated within the framework of multibody dynamics. It is shown that for an arbitrary cluster topology the governing equations can be given in an explicit scalar from. The derivation is based on the D'Alembert principle, on inertial coordinate system for each body and direct utilization of the path matrix describing the topology. The scalar form of the equations is important in computer simulations of flow of granular-type materials. An illustrative example of a three-body system is given.

• Geomechanics and Engineering
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• v.8 no.6
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• pp.811-828
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• 2015

Proper modelling of the basal resistance terms is key in simulating the motion of fluidized granular flow. In this paper, standard depth-averaged governing equations of granular flow are used together with the classical Coulomb, Voellmy, and velocity dependent friction models (VDFM). A high-resolution modified TVDLF method is implemented to solve the partial differential equations without numerical oscillations. The effects of basal resistance terms on the motion of granular flows such as geometric shape evolution, travel times and final deposits are analyzed. Based on the numerical results, the predictions of the front and rear end positions and developing length of granular flow with Coulomb friction model show excellent agreements with experiment results reported by Hutter et al. (1995), and illustrate the validity of the numerical approach. For the Voellmy model, the higher value of turbulent coefficient than reality may obtain more reasonable predicted runout for the small-scale avalanche or granular flow. The energy exchange laws indicate that VDFM is different from the Coulomb and Voellmy models, although the flow characteristics of both three models fit the measurements and observations very well.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.46.2-46.2
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• 2008

• Journal of Korean Society on Water Environment
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• v.29 no.3
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• pp.377-382
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• 2013

Enriching anammox bacteria (AMX) in a lab-scale granular sequencing batch reactor using local digester centrate, we observed the significant enrichment of the filamentous-like bacterial population. These bacteria were revealed as novel bacterial species (termed CHL) belonging to Chlorobi/Bacteroidetes phyla via Denaturing Gradient Gel Electrophoresis (DGGE). Further, niche differentiation of AMX and CHL quantification was observed in granule and filament biomass, suggesting AMX was dominant in the granule and CHL was dominant in the filament. Therefore, it was confirmed the structural role of CHL was indeed to aid the granule formation of the AMX. In parallel, the physiological role of CHL was suspected to degrade biopolymers in the digester centrate using nitrate as an electron acceptor.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2385-2394
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• 1992

Granular solid propellants having energy and fast burning rate produce great thrusts within extremely short time intervals. Thus numerical researchs prevailed rather than experimental. Using a 2-phase fluid dynamics model among 1-dimensional 2-phase models, a numerical program was set up to describe reacting flow fields, moving boundary with oscillating pressure waves and constitutive laws research. It deserves special emphasis that correlations of convective heat transfer coefficient and viscous drag force among constitutive laws are tested and discussed because slight variations of their constants make a large influence on their results. In this calculations, some of correlations make the large difference in results. Therefore constitutive laws for convective heat transfer coefficient and viscous drag force need more considerations with experiments.

• Nuclear Engineering and Technology
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• v.43 no.6
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• pp.477-488
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• 2011

A formulation is proposed for modelling the process of intra-granular diffusion of fission gas during irradiation of $UO_2$ under both normal operating conditions and power transients. The concept represents a simple extension of the formulation of Speight, including an estimation of the contribution of bubble motion to fission gas diffusion. The resulting equation is formally identical to the diffusion equation adopted in most models that are based on the formulation of Speight, therefore retaining the advantages in terms of simplicity of the mathematical-numerical treatment and allowing application in integral fuel performance codes. The development of the new model proposed here relies on results obtained by means of molecular dynamics simulations as well as finite element computations. The formulation is proposed for incorporation in the TRANSURANUS fuel performance code.

• Journal of Korean Society on Water Environment
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• v.26 no.3
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• pp.491-496
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• 2010

This study aimed to obtain equilibrium concentration on adsorption removal of phosphorus by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical properties of activated carbon and dynamics of phosphorus removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. Phosphorus adsorption equilibrium reaching time of powdered activated carbon was reduced as the dosage of activated carbon increases, while granular activated carbon despite increased dosage did not have influence on adsorption equilibrium reaching times of phosphorus as well, taking more than 10 hours. It was also noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon on phosphorus was 4.26 which is bigger than those of granular activated carbon. The adsorption rate constant on phosphorus of powered activated carbon with low effective diameter and iodine number was highest as $8.888hr^{-1}$ and the effective pore diffusivity ($D_e$) was lowest as $2.45{\times}10^{-5}cm^2/hr$, and the value of phosphorus adsorption rate constant of granular activated carbon was $0.174{\sim}0.372hr^{-1}$, It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter was better and its rate constant was also high.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.311-316
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• 2008

This study aimed to obtain equilibrium concentration on adsorption removal of ammonia nitrogen by activated carbon, to express the adsorption characteristics following Freundlich isotherm and also, based on the value obtained, to investigate the relationship between physical characteristics of activated carbon and dynamics of ammonia nitrogen removal by obtaining rate constant and effective pore diffusivity. The results summarized from this study are as follows. It was noted that powdered activated carbon showed better adsorption ability than granular activated carbon. The value of constant (f) of Freundlich isotherm of powered activated carbon was $4.6{\times}10^{-8}$ which is bigger than that of granular activated carbon. The adsorption rate constant on ammonia nitrogen of powered activated carbon with high porosity and low effective diameter was highest as 0.416 hr-1 and the effective pore diffusivity ($D_e$) was lowest as $1.17{\times}10^{-6}cm^2/hr$, and the value of ammonia nitrogen adsorption rate constant of granular activated carbon was $0.149{\sim}0.195hr^{-1}$. It was revealed that, with the same amount of dosage, the adsorptive power of activated carbon with lower effective diameter and bigger porosity was better and its rate constant was also high. With a little adsorbent dosage of 2 g, there was no difference removal ability of ammonia nitrogen as change of adsorption properties.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.746-756
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• 2004

포화토의 거동은 흙과 유체사이의 상호작용에 의해 지배된다. 특히, 동화중 작용시 포화된 사질토에서는 이러한 상호작용에 의해 급격한 액상화 현상이 유발되며 이는 동역학직, 유체역학직으로 복합적인 거동을 나타네어 복합하므로 오직 수치해석적인 방법을 이용한 거동해석만이 가능하다. 본 연구는 사질토에서의 동적 거동해석을 위한 수치해석기법 개발에 그 목적을 두었다. 본 수치해석기법은 Hiremath (1987, 1996)의 "Dynamics for Saturated Soils" 이론에 Sandhu (1975a, 1975b, 1976)의 Variational 기법을 적용하여 개발되었으며 간극수압과 관련된 다양한 토질역학적 문제들에 적용될 수 있을 것으로 기대된다.

• Journal of Adhesion and Interface
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• v.14 no.4
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• pp.183-191
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• 2013

In order to elucidate the granular heaping phenomenon, the movement behaviors of 3 different types of granule (millet, sand and thin foil disc) have been investigated by applying the vertical or the rotational vibration to each of the 3 vessels, respectively containing one of the 3 types of granule. In case of vertical vibrations, all of them showed the heaping phenomenon like Gerner's simulation, and that in the order of the millet, sand and thin foil disc, regardlessly of weight. Especially, a heaping of disc granules was proven to be relatively delayed, and that with several small complex clutters. For rotational vibration, the central area of vessel turned out to rise up due to the repulsive force by vessel wall as well as the collision between elastic granules, right after the turning point of vibration. Even spiral pattern was made when the rotational vibration amplitude got higher. From these facts, one can see that the heaping be characterized by the inclusion of attractive granules as well as the vibrational type applied to granule vessel.