• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.176-181
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• 2006

Experiments of Counter-Current Flow Limit(CCFL or Flooding) is performed to improve the drawbacks of Wallis' Correlation which neglects the effects of channel size, channel length, injection method and the boundary conditions at the inlet of liquid and gas phase. In this study, CCFL is observed by changing shape of porous plate using air and water. Results show that as the size of porous increases, CCFL with round shape of the porous plate decreases. In the present study, a CCFL correlation is developed and the CCFL map is proposed based on the present experimental results. developed by this experimental study.

• Journal of the Korean Society of Visualization
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• v.18 no.3
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• pp.35-41
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• 2020

We conduct numerical simulations of the interaction of a deformable structure with two-phase compressible flow. The finite volume method (FVM) is used to simulate fluid phenomena including a shock wave, a gas bubble, and the deformation of free surface. The deformation of a floating structure is computed with the finite element method (FEM). The compressible two-phase volume of fluid (VOF) method is used for the generation and development of a cavitation bubble, and the immersed boundary method (IBM) is used to impose the effect of the structure on the fluid domain. The result of the simulation shows the generation of a shock wave, and the expansion of the bubble. Also, the deformation of the structure due to the hydrodynamic loading by the explosion is identified.

• Earthquakes and Structures
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• v.22 no.4
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• pp.431-437
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.155-164
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• 2004

In order for studying pressure-coupled dynamic responses of droplet vaporization, open-loop experiment of an isolated droplet vaporization exposed to pressure perturbations in stagnant gaseous environment is numerically conducted, Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous nitrogen. Results show that wave instability in view of pressure-coupled vaporization response seems more susceptible at higher pressures and higher wave frequencies. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Augmentation of perturbation frequency also enhances amplification due to the reduction of phase differences between pressure perturbation and surface temperature fluctuation.

• Earthquakes and Structures
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• v.22 no.5
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• pp.439-445
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• 2022

One of the best choice for transportation of oil and gas at the end of rivers or seas is concrete pipelines. In this article, a concrete pipe at the end of river is assumed under the earthquake load. The Classic shell theory is applied for the modelling and the corresponding motion equations are derived by energy method. An external force induced by fluid around the pipe is asssumed in the final motion equations. For the solution of motion equations, the differential quadrature method (DQM) and Newmark method are applied for deriving the dynamic deflection of the pipe. The effects of various parameters including boundary conditions, fluid and length to thickness ratio are presented on the seismic response of the concrete pipe. The outcomes show that the clamped pipe has lower dynamic deflection with respect to simply pipe. In addition, with the effect of fluid, the dynamic defelction is increased significantly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.323-330
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• 2010

The time in port for vessels is one of the important factors for analyzing the operation status and the capacity of ports. In addition, the time in port for vessels can be directly used for estimating the greenhouse gas emissions resulted from vessels in port. However, it is unclear which variables can affect the time in port for vessels and what the marginal effect of each variable is. With these challenges in mind, the study analyzes the time in port for vessels arriving and departing port of Busan by using a parametric survival model. The results show that the log-logistic accelerated failure time model is appropriate to explain the time in port for 19,167 vessels arriving and departing port of Busan in 2008, in which the time in port is significantly affected by gross tonnage of vessels, service capacity of terminal, and vessel type. This study also shows that the greenhouse gas emission resulted from full-container vessels, which accounted for about 61% of all vessels with loading/unloading purpose arriving and departing port of Busan in 2008, is about "17 ton/vessel" in the boundary of port of Busan. However, the hotelling greenhouse gas emissions resulted from non-container vessels (3,774 vessels; 20%) are greater than those from the full-container vessels. Hence, it is necessary to take into account more efficient port management polices and technologies to reduce the service time of non-container vessels in port of Busan.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.130-137
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• 2008

$La_{0.7}Sr_{0.3}MnO_3$ films were deposited on $SiO_2$/Si and Si substrates annealed at $350^{\circ}C$ by rf magnetron sputtering. The oxygen gas flow rates were varied as 0, 40, and 80 sccm. Without post annealing process, $La_{0.7}Sr_{0.3}MnO_3$ thin films on $SiO_2$/Si and Si substrates were polycrystalline with (100), (110), and (200) growth planes. The grain size of $La_{0.7}Sr_{0.3}MnO_3$ thin films was increased with increasing oxygen gas flow rate. The sheet resistance of $La_{0.7}Sr_{0.3}MnO_3$ thin films was decreased with oxygen flow rate due to the increased grain size which induced a reduction of grain boundary. TCR (temperature coefficient of resistance) values of $La_{0.7}Sr_{0.3}MnO_3$ thin films were obtained from -2.0% to -2.2%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.30-35
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• 2021

The present study examined the effects of various guide fin structures and boundary parameters on the thermal performance of heat exchangers used in heat recovery thermoelectric generators. The heat transfer rate and pressure drop of the heat exchangers without fins, with circular fins, with triangular fins, and with combined circular and triangular fins were simulated numerically using ANSYS 19.1 commercial code to confirm the effect of the guide fin structures. The heat transfer rate of the heat exchanger with combined fins was 27.0%, 5.2%, and 1.5% higher than those without fins, with circular fins, and with triangular fins, respectively. The pressure drop characteristic of the heat exchanger with the combined fins was 28.3% higher than that without fins but 9.2% and 10.5% lower than those with circular fins and with triangular fins, respectively. The heat exchanger with combined fins as the optimal model showed the highest heat transfer rate of 5664.9 W and pressure drop of 1454.02 Pa for highest hot gas temperature, maximum flow rates of hot gas and coolant, and lowest coolant temperature.

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.65-71
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• 2009

Hydraulic fracturing technology has been widely applied in the industry for the recovery of the natural resources such as gas, oil and geothermal heat from hot dry rock. During hydraulic fracturing stimulation, multiple cracks are created resulting in mechanical interaction between cracks. Such an interaction influences obtaining hydraulic fracturing key parameters (crack opening, length, and borehole net pressure). The boundary collocation method (BCM) has been proved to be very effective in considering mechanical interaction. However, for better confidence, it needs to be verified by comparison with analytical solutions such as stress intensity factors. In this paper, three cases, single fracture in remote uniaxial tension, single fracture in remote shear stress field and two arbitrary segments in an infinite plane loaded at infinity are considered. As a result, the BCM is proved to be valid technique to consider mechanical interaction between cracks and can be used to estimate the hydraulic fracturing parameters such as opening of the fracture, and so on.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3125-3134
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• 2010

Three-way catalyst durability in the Korea requires 5 years/80,000km in 1988 but require 10 years/120,000km after 2002. Domestic three-way catalyst satisfies exhaust gas conversion efficiency or pressure drop etc. but don't satisfy thermal durability. Three-way catalyst maintains high temperature in interior domain but maintain low temperature on outside surface. This study evaluated thermal durability of three-way catalyst by thermal flow and structure analysis and the procedure is as followings. Thermal flow parameters ranges were determined by vehicle test and basic thermal flow analysis. Response surface for rear catalyst temperature was constructed using the design of experiment (DOE) for thermal flow parameters. Thermal flow parameters for rear catalyst temperature in vehicles examination were predicted by desirability function. Temperature distribution of three-way catalyst was estimated by thermal flow analysis for predicted thermal flow parameters.