• Korea-Australia Rheology Journal
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• v.15 no.2
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• pp.83-90
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• 2003

In cases of the microfluidic channel, the electrokinetic influence on the transport behavior can be found. The externally applied body force originated from the electrostatic interaction between the nonlinear Poisson-Boltzmann field and the flow-induced electrical field is applied in the equation of motion. The electrostatic potential profile is computed a priori by applying the finite difference scheme, and an analytical solution to the Navier-Stokes equation of motion for slit-like microchannel is obtained via the Green's function. An explicit analytical expression for the induced electrokinetic potential is derived as functions of relevant physicochemical parameters. The effects of the electric double layer, the zeta potential of the solid surface, and the charge condition of the channel wall on the velocity profile as well as the electroviscous behavior are examined. With increases in either electric double layer or zeta potential, the average fluid velocity in the channel of same charge is entirely reduced, whereas the electroviscous effect becomes stronger. We observed an opposite behavior in the channel of opposite charge, where the attractive electrostatic interactions are presented.

• Structural Engineering and Mechanics
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• v.66 no.3
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• pp.411-421
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• 2018

Although a rubber isolation cushion can reduce the dynamic response of a structure itself, it has little influence on the height of a sloshing wave and even may induce magnification action. Vertical baffles are set into a base-isolated Concrete Rectangular Liquid Storage Structure (CRLSS), and baffles are opened as holes to increase the energy dissipation of the damping. Problems of liquid nonlinear motion caused by baffles are described using the Navier-Stokes equation, and the space model of CRLSS is established considering the Fluid-Solid Interaction (FSI) based on the Finite Element Method (FEM). The dynamic response of an isolated CRLSS with various baffles under an earthquake is analyzed, and the results are compared. The results show that when the baffle number is certain, the greater the number of holes in baffles, the worse the damping effects; when a single baffle with holes is set in juxtaposition and double baffles with holes are formed, although some of the dynamic response will slightly increase, the wallboard strain and the height of the sloshing wave evidently decrease. A configuration with fewer holes in the baffles and a greater number of baffles is more helpful to prevent the occurrence of two failure modes: wallboard leakage and excessive sloshing height.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.301-307
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• 2003

In this study, we Presented computational results on the blood flow in the sac of the Korean artificial heart. Two dimensional unsteady flow was assumed and we utilized a finite element commercial code ADINA to simulate the blood flow. Rigid body-solid contact were considered between the actuator and the blood sac and fluid-structure interaction between the blood and the sac. The three geometric models proposed in the design process were simulated to assess the hemodynamic characteristics of the models According to the computational results, a strong flow to the outlet and a stagnated flow region near the inlet were observed during systole. The sac was filled with blood and recirculating flow was generated near the outlet during diastole. Shear stress during systole had its extreme values near the outlet edge whereas the magnitude of shear stress values were relative)v high near the inlet edge and the contacting surface with the actuator.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.59-62
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• 2009

유체-고체 상호작용(FSI)은 산업전반에서 꼭 필요한 분야이면서도 쉽게 접근하기가 어려운 전산역학 분야의 난제 중 하나이다. 유체-고체 상호작용의 전산해석에서 유체와 고체 사이의 불일치 격자망을 어떻게 처리하는가는 매우 어렵고 민감한 부분이 된다. 운동학적 연속성과 계면을 따른 응력의 평형을 추적하기 위해 유체와 고체의 계면에서는 각각의 영역에서 해석된 물리량들을 다른 영역으로 정확히 전달해야 하는데 대부분의 유체-고체 상호작용의 문제들은 불일치 격자를 가지고 있기 때문에 불일치 격자망을 효과적으로 처리하는 수단이 필요하다. 그래서 넓은 분야에 걸쳐 적용 가능한 유체 고체 상호작용 문제에 대한 효과적인 해석방법의 제안이 큰 의미를 갖는다고 생각한다. 따라서 본 연구에서는 유체-고체 계면의 운동을 이동최소제곱 기반의 변절점 요소를 사용하여 모사함으로써 2차원 유체-고체의 상호작용(FSI)을 위한 새로운 접근방법을 제시하였다.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.463-468
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• 2001

This paper presents the methodology for thermal hydraulic analysis of Pressurized Water Reactor (PWR) steam generators. Topics include porous media approach, governing equations, physical models and correlations for solid-to-fluid interaction and heat transfer and numerical solution scheme. Some details about the ATHOS3 code currently used widely for thermal hydraulic analysis of PWR steam generators in the industry are presented. The ATHOS3 code is applied to the thermal hydraulic analysis of steam generator in the Korea YGN 3&4 nuclear power plant and the computed results are presented.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.106-111
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• 2001

This paper presents the numerical methodology of ATHOS3 code for thermal hydraulic analysis of Pressurized Water Reactor (PWR) steam generators. Topics include porous media approach, governing equations, physical models and correlations for solid-to-fluid interaction and heat transfer, and numerical solution scheme. The ATHOS3 code is applied to the thermal hydraulic analysis of steam generator in the Korea Kori Unit-1 nuclear power plant and the computed results are presented.

• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.67-75
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• 2000

Computational fluid dynamics(CFD) analysis of the thermal flow in a municipal solid waste(MSW) incinerator combustion chamber provides crucial insight on the incinerator performance. However, the combustion of the waste bed is typically treated as an arbitrarily selected profile of combustion gas. A strategy for simultaneous simulation of the waste bed combustion and the thermal flow fields in the furnace chamber was introduced to substitute the simple inlet condition. A waste bed combustion model was constructed to predict the progress of combustion in the bed and corresponding generation of the gas phase species, which assumes the moving bed as a packed bed of homogeneous fuel particles. When coupled with CFD, it provides boundary conditions such as gas temperature and species distribution over the grate, and receives radiative heat flux from CFD. The combined simulation successfully predicted the physical processes of the waste bed combustion and its interaction with the flow fields for various design and operating parameters, which was limited in the previous CFD simulations.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.68-74
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• 2006

In the development of new automobiles, the efforts to reduce environmental problems like air pollution have been risen. Blowby gas consists of about $20{\sim}35%$ of total amount of Hydrocarbon (HC), one of dangerous pollutants issuing from automobiles. A PCV valve is a very small component in an automotive engine but it is a very important part. Because that a PCV valve is used to control blowby gas and to recirculate it into a manifold automatically. Although it has very simple operating principle, designing a PCV valve is so difficult due to interaction between fluid and solid. In this study, our purpose is to develop a design program for a PCV valve and to verify its efficiency. Both Bernoulli equation and 4th order Runge-Kutta method were adopted to predict spool displacements and flow patterns. Comparing with experiments, it was found that both spool diameters and displacements were predicted well, however, flow rates showed a little differences because of the assumption of non viscous flow.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.534-537
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• 2012

Hydroelastic effects on sloshing phenomena in a rectangular tank are numerically investigated. The dimension of the tank is $1000mm{\times}600mm$, and the filling ratio of water is 20% of tank height. One of the side walls of tank is assumed to be flexible. The tank is excited into sway motion with amplitude of 100mm and frequency of 0.53Hz that is first natural frequency of water inside the tank. Prediction results for time histories of pressure and displacement of flexible and rigid walls are compared to quantitatively assess hydroelastic effects on sloshing phenomena.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.108-115
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• 2002

The fundamental mechanism of a dispersed two-phase flow was investigated. Experiments were carried out to understand how the particles behaves under the influence of the particle size, shape, metamorphoses (bubble) and buoyancy of a single particle which is ascending from the standstill water. Two CCD cameras were employed for image processing of the behavior of the particles and the surrounding flow, which was interpreted with the technique of correlation PIV (Particle Image Velocimetry) and PTV (Particle Tracking Veloci- metry), respectively The experimental results showed that the large density difference bet- ween a particle and water caused high relative velocity and induced zigzag motion of the particle. Furthermore, the turbulence intensity of a bubble was about twice the case of the spherical solid particle of similar diameter.