• Communications of the Korean Mathematical Society
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• v.22 no.4
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• pp.587-596
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• 2007

In this paper, we study two-phase flow models. The chunk mix model of the two-phase flow equations is analyzed by a characteristic analysis. The model discussed herein has real characteristic values for all physically acceptable states and except for a set of measure zero has a complete set of characteristic vectors in state space.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.85-90
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• 2013

A numerical analysis for the internal flow was carried out in order to analyze the leakage flow characteristics inside the damped bypass valve. This research has found that the valve characteristics became stable at above a specific temperature. Very small amount of leakage flow was occurred. But there was no effect in temperature. The more temperature fell, the more maximum pressure rate was increased.

• Corrosion Science and Technology
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• v.17 no.6
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• pp.317-323
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• 2018

Assumptions have always been that wall thinning on the secondary side piping in nuclear power plants is mostly caused by Flow-Accelerated Corrosion (FAC). Recent studies have showed that wall thinning on the secondary side piping is caused by Liquid Droplet Impingement Erosion (LDIE), Solid Particle Erosion (SPE), cavitation, and flashing. To manage those aging mechanisms, several software such as CHECWORKS, COMSY, and BRT-CICERO have been used in nuclear power plants. Korean nuclear power plants have been using the CHECWORKS program since 1996 to date. However, many site engineers have experienced a lot of inconveniences and problems in using the CHECWORKS program. In order to work through the inconveniences and to remedy problems, KEPCO-E&C has developed a "3D-based pipe wall thinning management program (ToSPACE)" based on the experience of over 30 years in relation to the pipe wall thinning management. This study compares the results of FAC and LDIE analysis using both the CHECWORKS and ToSPACE programs with respect to validation of the wall thinning analysis results.

• Journal of the Korean Society of Visualization
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• v.7 no.2
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• pp.42-46
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• 2010

In this paper we report the method of visualizing and measuring the fluid flow within a small droplet of millimeter size. We use a vertical laser sheet in visualization of the micrometer size and special attention is given to the arrangement of microscope to obtain clear images. Then we use a PIV technique to measure the velocity of the internal flow from the images taken. Since the droplet is of spherical shape, the images represent highly deteriorated picture of the real objects due to the refraction phenomenon. In order to compensate the refraction, we in this study developed two kinds of methods for the real velocity. In the first method, the refracted images are directly used to obtain the velocity in the image space, and then the velocity is transformed to the real space. In the second method the images are first transformed to the real-space objects, and then the PIV is used to measure the velocity field. We compared the two results to prove the usefulness of the compensation technique.

• Journal of the Korean Society of Industry Convergence
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• v.3 no.3
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• pp.245-250
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• 2000

This study was carried out to investigate blowing performance for blowing type in space heater. This paper present that power requirement, static pressure, total pressure and static pressure efficiency were increased in proportion to air flow rate. And in the Korean space heater, side ward blowing type was effected than downward blowing type.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.323-324
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• 2012

Flammability limits of opposed flow diffusion flame in a narrow channel was investigated experimentally and theoretically. There were three different extinction modes corresponding to high strain rate (HSR), low strain rate (LSR) and dilution ratio (DR) limits. To investigate these limits, a theoretical study was followed by focusing on flow and heat transfer characteristics. Consequently, a dead space concept that has been used for premixed flames was important to reveal the heat loss mechanism in a narrow channel especially for LSR conditions even in the case of diffusion flames.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.5
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• pp.101-108
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• 2002

A numerical simulation of an incompressible cavity flow is conducted. Two dimensional Navier-Stokes equations are integrated using staggered grid and a finite volume method with C-QUICK scheme for spatial derivatives and fully implicit scheme for the time derivatives. SIMPLE-C algorithm is employed to solve the pressure field. Computational results show that the third eddy is generated in the shear layer mode but not in the steady mode. This signifies that the third eddy plays an important role in cavity flow stability. As a means to control the flow, jet blowing is applied to a position below the cavity upstream edge. Effects of flow control parameters on the stability such as the frequency, the phase, and the velocity magnitude are reported.

• International Journal of Fluid Machinery and Systems
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• v.9 no.3
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• pp.256-264
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• 2016

To meet the demand of higher handling capacity, a mixed-flow submersible deep well pump was designed and tested. The main hydraulic components are made of plastics, which is free of erosion, light-weight, and environment-friendly. To simplify plastic molding process, and to improve productivity, an axial-radial guide vane was proposed. To clarify its effect on the performance, a radial guide vane and a space guide vane are developed as well. By comparison, the efficiency of the pump equipped with the axial-radial guide vane is higher than the radial guide vane and is lower than the space guide vane, and its high efficiency range is wide. The static pressure recovery of the axial guide vane is a bit lower than the space guide vane, but it is much larger than the radial guide vane. Taking the cost and molding complexity into consideration, the axial-radial guide vane is much economic, promoting its popularity for the moderate and high specific speed submersible deep well pumps.

• Proceedings of the Korea Contents Association Conference
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• 2016.05a
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• pp.239-240
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• 2016

Traditional town with wooden houses like Japanese historic local town is vulnerable to disaster. Wooden houses crowed in this study area, there is no gap between buildings and buildings. When disaster occurs, they can not use evacuation routes based on the value of probability of rubble flow. Disaster prevention design of traditional town using spatial information for residents is a modern idea in the field of disaster prevention study. Therefore, it is basically important and effective to create information, especially on the current situation such as dangerousness of the area. Here, we report on a disaster prevention design regarding probability of street blockade and probability of rubble flow at a large earthquake directly under our study area. In this study, we explain about necessity of temporary evacuation areas like open space. As a result, we found some ideas to secure evacuation routes from traditional houses to designated refuge places using temporary evacuation areas.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.11
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• pp.957-962
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• 2007

The flow around a rotating circular cylinder near a plane wall is investigated by the measurement of the lift acting on the cylinder and by the flow visualization using the hydrogen bubble technique in the circulating water tank. The experimental parameters are the rotating direction of the cylinder, the space ratios H/D($H/D=0.05{\sim}0.5$) between cylinder and plane wall and the velocity ratios ${\alpha}({\alpha}=0{\sim}{\pm}2.0)$. In the case of clockwise, the lift on the rotating circular cylinder was increased with the reduction of the space ratios and with the velocity ratios, the upper separation point was more shifted in the rotating direction with them. In the case of anticlockwise, the absolute value of the lift on the rotating circular cylinder was increased with the space ratios and with the velocity ratios, the lower separation point was more shifted in the rotating direction with them.