• Korean Journal of Hydrosciences
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• v.2
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• pp.13-24
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• 1991

The governing partial differential equation of flow in porous media is developed on the bases of the continuity equation of fluid for transient flow through a saturated-unsaturated zone, and substitution of Dercy's law. The numerical solution is obtained by the Galerkin finite element method based on the principle of weighted residuals. The analysis is carried out by using the unsteady storm data observed and the functional relationships between the hydraulic conductivities, capillary pressure heads, and volumetric water contents under saturated-unsaturated conditions. As the results the hydraulic conductivities, rates of change of storage and initial moisture conditions are significantly influened on the responses of subsurface flow on a hillslope.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.21-24
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• 2005

A computational analysis of hygro-thermal and mechanical behaviour of concrete column at high temperature is presented. The objective of this study is to develop a finite difference model that simulates coupled heat and transport phenomena in reinforced concrete structures exposed to rapid heating conditions such as fires. The theoretical basis for the integrated finite difference method is presented to describe a powerful numerical technique for solving of fluid flow in porous media. The numerical results predict the phenomena of 'moisture clog' and the explosive spalling of concrete under fire. The investigations show that high-strength concrete(HSC) and normal-strength concrete(NSC) exposed to high temperature have different pore pressure buildup dependent on porosity, permeability and moisture contents. HSC has more possibility than NSC on spalling.

• KSBB Journal
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• v.10 no.5
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• pp.482-490
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• 1995

The relationship between pressure drop and liquid flow rate, for an axial and a radial flow chromatographic column packed with compressible porous media was theoretically analyzed using modified Kozeny-Carman equation. The results were compared with experimental observations obtained using compressible DEAE-agarose as a model medium. At 2-9 psi range studied, the theoretical derivation accounting for 'gel compression' effect predicted simple Langmuirian type response of volumetric flow rate to changes in pressure drop. On the other hand, the experimental response was more or less sigmoidal. At the same pressure drop, radial column showed 2-3 times higher flow rates than those of axial column both theoretically and experimentally. Using r-HBsAg crude extract, protein resolution effects between the two types of columns at different flow rates were compared side-by-side. It turned out that, though general chromatographic behavior was very similar, axial column was somewhat superior in terms of r-HBsAg recovery yield and specificity. However, the number of theoretical plates analysis indicated the protein resolution effects were comparable.

• Magazine of the Korean Society of Agricultural Engineers
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• v.9 no.2
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• pp.1301-1305
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• 1967

Ground water flow can be studied with model test. Model test of ground water works are necessary for economic and safe design of the works. Also influence of the ground water flow to the durability and safety of hydraulic structures can be studied with this model. a. Sand model ; Water flow through porous media is the principle of sand model. Darcy's formula is the basic equation, $q=k{\frac{dh}{ds}}^{\circ}. The effect of the ground water flow on the grain system itself is represented with this model only. b. Hele-Shaw model ; In this model use is made of the viscous flow analogy. Viscous fluid such as glycerine flowing through two parallel plates depends on Poiseuille law, $q=-c{\frac{dh}{ds}}$. The analogue can be used vertically and horizontally. c. Heat model ; This is based on the analogy of the Fourier's law for heat conduction and Darcy's law for ground water flow. Especially unsteady problem can be studied with this model. A difficulty of the construction of this model is the isolation, which has to prevent losses of the heat. d. Electirc model ; Ohm's law for electric current is analogous to Darcy's law. Resistance material such as metal foil, graphite block, water with salt added, gelatine with salt added, ete. is connected to electric sources and resistor, and equi-voltage line is detected with galvanometer, $N_aCl$, $CuSo_4$, etc. are used as salt in the model. e. Membrane model ; This model is based on the facts that the deflection of a thin membrane obeys Laplace's equation if there is no load in the direction perpendicular to the membrane, and if the dellection is small.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.7
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• pp.55-63
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• 2006

Bacterial transport models were evaluated in this study to determine the suitable model at describing bacterial transport in saturated column experiments. Four models used in the evaluation were: advective-dispersive equation (ADE) + equilibrium sorption/retardation (ER) + kinetic reversible sorption (KR) (Model I), ADE + two-site sorption (Model 2), ADE + ER + kinetic irreversible sorption (KI) (Model 3), ADE + KR + KI (Model 4). Firstly, analyses were performed with the first experimental data, showing that Model 4 is appropriate for describing bacterial transport. Even if Model 1 and 2 fit well to the observed data, they have a defect of not including the irreversible sorption, which is directly related to mass loss of bacteria. Model 3 can not properly describe the tailing observed in the data. However, further analysis with the second data indicates that Model 4 can not describe retardation of bacteria, even if the sorption-related parameters are varied. Therefore, Model 4 is modified by incorporating retardation factor into the model, resulting in the improved fitting to the data. It indicates that the transport model, into which retardation, kinetic reversible sorption, and kinetic irreversible sorption are incorporated, is suitable at describing bacterial transport in saturated column experiments. It is expected that the selected transport model could be applied to properly analyze the bacterial transport in saturated porous media.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5B
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• pp.483-489
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• 2011

In this study, the coupled-numerical model has been newly developed to investigate numerically scouring and deposition around a coastal structure like a submerged breakwater using a numerical wave model and a lagrangian particle model for sand transport. As a numerical wave model, LES-WASS-2D (Hur and Choi, 2008) is adopted. The model is able to consider the flow through a porous midium with inertial, laminar and turbulent resistance term and determine the eddy viscosity with LES turbulence model. Distinct element method (Cundall and Strack, 1979), which is able to apply to many dynamical analysis of particulate media, as a lagrangian particle model for sand transport is newly coupled to the numerical wave model. The numerical simulation has been carried out to examine the scour problem in front of an impermeable submerged breakwater using the newly coupled-numerical model. The numerical results has been compared qualitatively with an existing experimental data and then its applicability has been discussed.

• Journal of Ocean Engineering and Technology
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• v.24 no.2
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• pp.1-9
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• 2010

Oscillating Water Column is one of the most widely used converting systems all over the world. The operating performance is influenced by the efficiencies of the two converting stages in the OWC chamber-turbine integrated system. In order to study the effects of the pressure drop induced by the air turbine, the experiments using the impulse turbine and the orifice device are carried out in the wave simulator test rig. The numerical simulation utilizing the orifice and porous media modules is calculated and validated by the corresponding experimental data. The numerical wave tank based on the two-phase VOF model embedded with the above modules is employed to investigate the wave elevation, pressure variation inside the chamber and the air flow velocity in the duct. The effects of the air turbine on the integrated system and interaction among the wave elevation, pressure and air flow velocities variations are investigated, which demonstrates that the present numerical model are more accurate to be employed.

• Journal of Hydrogen and New Energy
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• v.24 no.5
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• pp.386-392
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• 2013

Polymer electrolyte membrane (PEM) fuel cell stacks are constructed by stacking several to hundreds of unit cells depending on their power outputs required. Fuel and oxidant are distributed to each cell of a stack through so-called manifolds during its operation. In designing a stack, if the manifold sizes are too small, the fuel and oxidant would be maldistributed among the cells. On the contrary, the volume of the stack would be too large if the manifolds are oversized. In this study, we present a three-dimensional computational fluid dynamics (CFD) model with a geometrically simplified flow-field to optimize the size of the manifolds of a stack. The flow-field of the stack was simplified as a straight channel filled with porous media to reduce the number of computational meshes required for CFD simulations. Using the CFD model, we determined the size of the oxidant manifold of a 30 kW-class PEM fuel cell stack that comprises 99 cells. The stack with the optimal manifold size showed a quite uniform distribution of the cell voltages across the entire cells.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.263-270
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• 2016

Recent Engineered nanoparticles were increasingly exposed to environmental system with the wide application and production of nanomaterials, concerns are increasing about their environmental risk to soil and groundwater system. In order to assess the transport behavior of silver nanoparticles (AgNPs), a saturated packed column experiments were examined. Inductively coupled plasma-mass spectrometry and a DLS detector was used for concentration and size measurement of AgNPs. The column experiment results showed that solution chemistry had a considerable temporal deposition of AgNPs on the porous media of solid glass beads. In column experiment, comparable mobility improvement of AgNPs were observed by changing solution chemistry conditions from salts (in both NaCl and $CaCl_2$ solutions) to DI conditions, but in much lower ionic strength (IS) with $CaCl_2$. Additionally, the fitted parameters with two-site kinetic attachment model form the experimental breakthrough curves (BTCs) were associated that the retention rates of the AgNPs aggregates were enhanced with increasing IS under both NaCl and $CaCl_2$ solutions.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2540-2543
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• 2008

Liquid crystal displays (LCD's) are continuously coated with some chemicals in the clean room of a factory. Spreading of these chemicals is causing serious problems both in controlling clean room quality as well as to the workers inside the factory. It is required to alleviate or properly control the offensive odor which is mainly composed of propylene glycol mono ethyl acetate, novolak resin and photo active compound. The control strategy employed is to bleed the offensive odor gas out the clean room. A full scale 3D CFD model was created with anisotropic porous media, chemical species transport with no volumetric reaction, and thermal diffusion with propane gas (tracer gas) to simulate the odor spreading. A segregated implicit solver with standard k-$\varepsilon$ model is employed. The detailed CFD analysis made it possible to develop an effective method of ventilating the coater room and optimizing their capacities.