• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.203-206
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• 2004

To analysis the electrokinetic phenomena in the ground dependent on the way of applied electric power, such as constant current and constant voltage, the governing equations are derived considering advection, diffusion, ionmigration, and then they were formulated using by finite difference method. The developed program is verified by comparing the tested and predicted results reported in present papers. The results indicate that the slightly small electrical potential is predicted for constant current and for constant voltage pH near to the cathode was small than the test results. But the other predictions including the final suction, pH of electrolyte and cumulative flow are similar to the test results and predictions.

• Journal of the korean society of oceanography
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• v.38 no.4
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• pp.157-165
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• 2003

In order to understand the characteristics of sedimentary environments in Ulleung Basin of the East Sea (Sea of Japan), three sediment cores were taken with a box corer during R/V Tamyang cruise in October 1999. Activities of $^{7}Be,{\;}^{210}Pb,{\;}^{226}Ra,{\;}^{234}Th,{\;}^{238}{\;}and{\;}^{137}Cs$ in sediment samples were determined by non-destructive gamma-ray spectrometry. Rates of sedimentation and particle mixing were estimated by best fitting an advection­diffusion particle mixing model to the data of $^{7}Be,{\;}^{234}Th,{\;}and{\;}^{210}Pb$. Estimated sedimentation rates were 0.06-0.08 cm/yr and particle mixing rates were $0.13-0.65{\;}\textrm{cm}^2/yr$. The use of multiple tracers in our study prevented us from probable up to 38% overestimation of sedimentation rates.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.1
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• pp.1-10
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• 2002

A three-dimensional numerical model which involved the nesting method was developed to reproduce the wind circulation of Kwangyang Bay area which comprises complicated mountains and sea topograph. The calculated results indicated geographical effects of Kwangyang Bay area, sea/land breezes and mount-valley wind which are local circular winds. We also noticed that the northern inland area of Kwangyang Bay formed the very complex wind systems under the influence of such geographic effects when a land breeze was not formed. A good agreement was found between predicted and observed values of temperature. In addition, the calculated results of the wind direction and the wind velocity are in accord with the observed values. They showed only a slight difference in between predicted and the observed values, when the sea breeze and the land breeze are changing.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.133-142
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• 2010

We calculated using siltation model to know the influnce of the tidal current, the tidal level, the sediment transport of seabed around sea area due to the construction of the Song do New city. We calculated the tidal current and based on this we estimated scour, sedimentation using the advection-diffusion equation and accessed the sediment transport of seabed before and after the construction of the New city. Sedimentation was increased in the east coast of Young jong Do, and Scour was increased according to the direction from the front route of north harbor to Ho do. Tidal level was increased overall.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.199-202
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• 2008

It is well-known fact that tidal difference between the ebb and flow in Yellow Sea is about 9 m so that it has largest value in the world. This wide range of tide level enables Yellow Sea water to intrude into main stream of Han River. However, the study of the tidal reach of Han River has not been carried out thoroughly since North and South Koreas share this region so that topography data and physical measurement are lacking. In this study, to examine the reverse flow and dispersion behavior by tidal effect at the tidal reach of Han River, 2-D river analysis models were applied. RMA-2 was applied to calculate the horizontal velocities and water surface elevation. With the results of velocities and water depth, RAM4, which is 2-D advection-dispersion model based on FEM was simulated to analyze the horizontal transport behavior of BOD.

• Nuclear Engineering and Technology
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• v.44 no.1
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• pp.79-88
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• 2012

Migration tests were performed with conservative tracers in a fractured zone that had a single fracture of about 2.5 m distance at the KURT. To interpret the migration of the tracers in the fractured rock, a solute transport model was developed. A two dimensional variable aperture channel model was adopted to describe the fractured path and hydrology, and a particle tracking method was used for solute transport. The simulation tried not only to develop a migration model of solutes for open flow environments but also to produce ideas for a better understanding of solute behaviours in indefinable fracture zones by comparing them to experimental results. The results of our simulations and experiments are described as elution and breakthrough curves, and are quantified by momentum analysis. The main retardation mechanism of nonsorbing tracers, including matrixdiffusion, was investigated.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.255-263
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• 2005

Migration experiments of THO and 237Np have performed through a sampled granite core in Chemlab2 probe at the Aspo hard Rock laboratory. The elution curves of THO were analysed to determine hydraulic properties such as the extent of dispersion effect according to flow rates. The retardation phenomena of the solutes were observed and described with elution curves and migration plumes. After migration test, the rock core was opened, and the remaining radioactivities on the rock fracture surfaces were measured. The transport process was simulated with a two-dimensional channel model. The mass transport process was described with three types of basic processes ; advection, sorption and matrix diffusion. By the combination of these processes, effects of each process on transport were described in terms of elution curves and migration plumes. By comparing the simulation results to the experimental one, it was possible to analyse the retardation effect quantitatively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.173-182
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• 1994

A numerical experiment on the effective discharge of waste materials caused in recirculating aquaculture basins was performed. The numerical model used in this study was a 4-level hydrodynamic and advection-diffusion model. Flow structures and settling processes of ss in the various mathematical model basins are discussed. The calculated flow fields of the numerical basin corresponded well with the measured velocity in field basin. In the cases of steep bottom slopes in 4/30, the non-dimensional tractive force($U{\ast}/U{\ast}_c$) which is all important parameter for the deposition pattern of waste materials was stronger than with the mild slope one. The settling pattern of ss depended considerably on the degree of bottom slope of basin. To concentrate deposited waste materials into the center discharge pipe, it is useful to design a cylindrical basin with a steeply conical bottom. In addition, to prevent movement of the deposit area away from the center, it is necessary to locate the circulating ducts at diametrically opposed points on the basin sides.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2460-2464
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• 2008

The present paper suggests new method to know the effects of molecular diffusion and the helicity of microchannel flows on mixing in passive micromixers, which are essential components of a microfluidic chip. In this study, 'Helix Index' is newly defined as the magnitude of chaotic advection. Relationship between Helix Index and Mixing Index is analyzed numerically such as the wide range of Peclet and Reynolds numbers in three dimensional serpentine microchannel when using soluble solutions (water/glycerol). As a result, a simple algebraic equation is derived by this relationship based on a regression analysis. The algebraic equation is found to be able to accurately predict the mixing performance without solving the coupled, complex momentum and mass transfer equations.

• Honam Mathematical Journal
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• v.38 no.1
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• pp.47-57
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• 2016

In the discrete formulation of the bubble stabilized Legendre Galerkin methods, the system of equations includes the artificial viscosity term as the parameter. We investigate the estimation of this parameter to get the least-squares solution which minimizes the sum of the squares of errors at each node points. Some numerical results are reported.