• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.877-895
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• 2016

This paper is concerned with the analytical derivation of natural sloshing frequencies of liquid in annular cylindrical tank and its verification by experiment. The whole liquid domain is divided into three simple sub-regions, and the region-wise linearized velocity potentials are derived by the separation of variables. Two sets of matrix equations for solving the natural sloshing frequencies are derived by enforcing the boundary conditions and the continuity conditions at the interfaces between sub-regions. In addition, the natural sloshing frequencies are measured by experiment and the numerical accuracy of the proposed analytical method is verified through the comparison between the analytical and experimental results. It is confirmed that the present analytical method provides the fundamental sloshing frequencies which are in an excellent agreement with the experiment. As well, the effects of the tank radial gap, the bottom flow gap and the liquid fill height on the fundamental sloshing frequency are parametrically investigated.

• Journal of Climate Change Research
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• v.8 no.4
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• pp.287-295
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• 2017

This paper provides a mathematical approach for estimating flood risks due to the effects of climate change by developing a one dimensional (1D) hydraulic model for the mountainous river reaches located close to the Yeongwol thermal power plant. Input data for the model, including topographical data and river discharges measured every 10 minutes from July $1^{st}$ to September $30^{th}$, 2013, were imported to a 1D hydraulic model. Climate change scenarios were estimated by referencing the climate change adaptation strategies of the government and historical information about the extreme flood event in 2006. The down stream boundary was determined as the friction slope, which is 0.001. The roughness coefficient of the main channels was determined to be 0.036. The results show the effectiveness of the riverbed widening strategy through the six flooding scenarios to reduce flood depth and flow velocity that impact on the power plant. In addition, the impact of upper Namhan River flow is more significant than Dong River.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.12
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• pp.1078-1087
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• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.827-831
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• 2009

Recently, frequency occurring flood and drought has increased the necessity of an effective water resources control and management of river flows. Therefore, the simulation of the flow distribution in natural rivers is great importance to the solution of a wide variety of practical flow problems in water resources engineering. However The serious problem facing two-dimensional hydraulic model is the treatment of wet and dry areas. The objective of this study is to investigate the wet and dry parameters that have direct relevance to model performance in situations where inundation of initially dry areas occurs. Several numerical simulations were carried out, which examined the performance of the marsh porosity method for the purpose of sensitivity analysis. Experimental channel and a variety of channel were performed for model tests. The results were compared with those of the observation data and simulation data of existing model. The RMA-2 model displayed reasonable flow distribution compare to the observation data and simulation data of existing model in dry area for application of natural river flow. As a result of this study, effectively applied marsh porosity method provide a reliable results for flow distribution of wet and dry area, it could be further developed to basis for extending to water quality and sediment transport analysis.

• Journal of Korea Water Resources Association
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• v.38 no.11
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• pp.973-984
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• 2005

A three-dimensional thermal hydrodynamic model is developed for carrying out unsteady simulation of the selective withdrawal of the stably stratified flow in a geometrically complex, natural reservoir The governing equations are discretized on a non-staggered grid using a second-order accurate, finite-volume scheme. The numerical model is validated by applying it to simulate three-dimensional, turbulent, stratified, shear-layer flow case. The numerical predictions appear to capture reasonably well the general shape of velocity and temperature profiles observed in the laboratory experiments, while significant overestimation of the magnitude of velocity profiles is observed in the application to the flow in a natural reservoir. The physics of selective withdrawal as emerge from the numerical simulations are also discussed.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.5
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• pp.438-444
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• 2015

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.6
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• pp.15-21
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• 2022

This study considered the internal flow considering the internal shape of the CNG filling nozzle, which is widely distributed in Korea. The CNG filling nozzle is the last part to pass through in the CNG filling process and has a significant influence on the filling efficiency. The mechanism was identified by disassembling the CNG filling nozzle and performing a flow analysis according to the mechanism. Consequently, the energy loss owing to eddy currents in the flow was determined, and modeling was proposed to reduce the energy loss by simplifying the shape and parts.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.10-13
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• 2010

The flow field in road tunnel is influenced by some facts such as piston effect of vehicle's move, operation of ventilation facilities, natural wind and buoyancy effect of fire plume. Among those, jet fan is one of main ventilation facilities especially in longitudinal ventilation system of tunnel. In this study to analyze tunnel flow induced by operation of jet fan, numerical simulation has been carried out. The velocity distributions and streamlines in tunnel are examined to consider the three-dimensional characteristics of tunnel flow caused by jet fan.

• Ocean and Polar Research
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• v.34 no.4
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• pp.395-401
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• 2012

Ten-year AVHRR sea surface temperature data obtained in the Yellow Sea are put into EOF analyses. Temperature variation is predominated by the first mode which is associated with the seasonal fluctuation of temperature with annual range decreasing with the bottom depth. Since such a strong annual signal may mask the upwind or downwind flows occurring intermittently during the winter, only the data obtained during this season are put into EOF analyses. Every winter shows similar results. The first mode, explaining more than 90% of total variance, appears to be a part of the seasonal variation of temperature mentioned above. In the second mode, the time coefficient is well correlated with northerly winds to which the responses of the trough and shallow coastal areas are opposite to each other. A simple theoretical consideration suggests the following physical explanation: The northerly wind stress anomaly creates an upwind (downwind) flow over the trough (coastal) areas, which then induces a temperature increase (decrease) by advection of heat, and vice versa for the southerly wind stress anomaly. Hence, this paper provides further evidence of the intermittent upwind or downwind flows occurring in the Yellow Sea every winter.

• Journal of Environmental Science International
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• v.20 no.5
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• pp.581-587
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• 2011

Industrial natural ventilation systems consist of gravity ventilator, the high/low windows and doors. Especially, the high windows play an important role in the industrial natural ventilation systems. Generally speaking, industrial high windows are divided into 3 types; louver type, $45^{\circ}$ open type and $90^{\circ}$ open type. This study was numerically and experimentally conducted. Three types of windows were tested to know the ventilation characteristics and estimate the ventilation efficiencies. Numerically, computational fluid dynamics software (AIR PAK Ver. 2.0) was used to observe the flow characteristics inside the industrial building and the concentration contours generated by the tracer gas method. Experimentally, the flow visualization technique and the tracer gas method were applied with the model building to characterize the flow pattern inside the model building and to estimate the ventilation efficiencies with the different windows. It was found that $90^{\circ}$ open type window was most effective for the discharge of pollutants from the industrial building. On the other hand, the louver type window was found to be less effective than any other windows.