• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.15-18
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• 1995

Three-dimensional steady and pulsatile flow experiments and numerical simulations have conducted to investigate the flow characteristics in the aortic bifurcation model. In vitro velocity measurements were made using both laser Doppler anemometry and pulsed Doppler ultrasound velocimetry. In this study, flow phenomena in the aortic bifurcation model are discussed extensively and the numerical results are compared with experimental results.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.1925-1930
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• 2006

A quasi depth-varying mathematical model for wind-generated circulation in coastal areas, expressed in terms of the depth-averaged horizontal velocity components and free surface elevation was validated and used to understand the diurnal circulation process. The wind velocity is considered as a dominant factor for driving the wind generated current. In this paper, three dimensional numerical experiments that included the land topography were used to investigate the mesoscale air flow over the coastal regions. The surface temperature of the inland was determined through the surface heat budget consideration with inclusion of a layer of vegetation. A series of numerical experiments were then carried out to investigate the diurnal response of the air flow and wind-generated circulation to various types of surface inhomogeneities.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.459-467
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• 2006

In this study, hydraulic and numerical model experiments were performed to analyze and improve the effects of flow-rate increase in the intake canal of Boryeong Thermal Power Plants on the flow condition in the circulation water pump (CWP) chambers. Based on the numerical simulation results, when the flow-rate increased in the circulation water intake canal, the velocity in the canal and vertical vorticities in the circulation water pump chambers increased and hence the vortex occurrence potential would be greatly increased. It was found by performing hydraulic model experiments that the velocity distribution near the bottom in the inlet of the circulation water pump chambers was highly non-uniform while the velocity distribution near the water surface was nearly uniform. To reduce the non-uniformity in the velocity distribution, triangular flow deflectors were devised. The installation of the flow deflectors in the inlet of circulation water pump chambers was successfully to reduce velocity non-uniformities and to remove flow reversal problems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.2
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• pp.213-221
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• 1985

Two dimensional laminar natural convection in a rectangular enclousure composed of a hot bottom wall, a partially cold side wall and insulated walls except the above walls was studied by numerical analysis and also by esperiments. In the experiments, the temperature distributions in the enclosure and Nusselt number distribution along the hot and cold walls were obtained by the use of Mach-Zehnder interferometer. At first, numerical analysis with the boundary conditions of the experimental apparatus was performed and the comparison of the results of the numerical and the experimental results validated the numerical model good ennough. Heat transfer characteristics were investigated by applying the verified numerical model with the parameters, i.e. Grashof number, aspect ratio, position of cold plate and insulation condition. The results showed the optimal conditions of temperature distribution and the position of cold wall, and the characteristics of insulation materials.

• Fire Science and Engineering
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• v.17 no.3
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• pp.50-54
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• 2003

The backlayer phenomena of smoke in the road tunnel is evaluated through numerical experiments. A commercial code, PHOENICS is used to simulate smoke flow in the road tunnel. The independent and dependent variables are ventilation air velocity and the length of backlayer of smoke respectively. Hybrid scheme and $textsc{k}-\varepsilon$ turbulence model is adopted in the simulation process and mass residual is used as a convergence criterion. The experimental results say that the length of backlayer is reduced linearly with the increase of ventilating air velocity and that there is a critical air velocity which prevents from the onset of backlayering phenomena. One finds that there is a fresh air region near the bottom of tunnel which could make the passenger escape from the region polluted by smoke. These phenomena come from the severe vertical stratification of the smoke air mixture in the tunnel.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.36-47
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• 2012

In this study, the control performance of resonator was reviewed through numerical analysis and 3-dimensional hydraulic model experiments by attaching the resonator suggested in the existing studies to the openings of rectangular harbor and breakwater placed in a straight line to reduce short-period waves. In the numerical analysis, linear analysis method of singularity distribution method based on vertical-line Green function and full non-linear analysis method by 3D-NIT model were applied, and the validity of the numerical analysis methods was verified through comparative analysis between results of hydraulic experiments and numerical analysis results. In addition, effectiveness of the resonator was confirmed by reviewing its control performance on the short-period waves through review on the comparison with the case in which the resonator is not attached.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.3
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• pp.41-52
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• 2020

This paper investigates the stress-reducing preventive maintenance model through numerical experiments. The preventive maintenance model is used to analyze the relationship between related conditions and variables to gain insight into the efficient operation of the system when performing preventive maintenance in real-world situations. Various preventive maintenance models have been developed over the past decades and their complexity has increased in recent years. Increasing complexity is essential to reflect reality, but recent models can only be interpreted through numerical experiments. The stress-reducing preventive maintenance is a newly introduced preventive maintenance concept and can only be interpreted numerically due to its complexity, and has received little attention because the concept is unfamiliar. Therefore, for information purposes, this paper investigates the characteristics of the stress-reducing preventive maintenance and the relationship between parameters and variables through numerical experiments. In particular, this paper is focusing on the economic feasibility of stress-reducing preventive maintenance by observing changes in the optimal preventive maintenance period in response to changes in environmental stress and the improvement factor. As a result, when either the environmental stress or the improve effect of stress-reducing preventive maintenance is low, it is not necessary to carry out the stress-reducing preventive maintenance at excessive cost. In addition, it was found that the age reduction model is more economical than the failure rate reduction model.

• Journal of the Korean earth science society
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• v.30 no.6
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• pp.709-720
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• 2009

Field observation and numerical experiments were conducted to understand the impact of water retention pavement on the surface heat budget and on the regional circulation. The numerical model applied in this study is the atmospheric dynamic model Local Circulation Model (LCM) with two dimensional grid system, and a field observation was carried out under the clear sky and calm conditions of the weather on 19 July 2007. In the field observation, the maximum value of surface temperature on pavement covered with water retention material reached the $41.2^{\circ}C$ at 1430 LST and the values was lower for $16.1^{\circ}C$ than that of asphalt without the material. The Case BET03 assumed to be 0.3 for the surface evaporation efficiency was in good agreement with the observation and its sensible and latent heat fluxes were numerically estimated to be 229 and 227 $W/m^2$, respectively. Results of the numerical experiments demonstrated that the water retention pavement tends to induce the increase of latent heat flux associated with the lower surface temperature and mixing height during the daytime. Discontinuity of latent heat caused by the water retention pavement also tends to promote the development of mesoscale circulation called as land-land breeze or country breeze.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.83-92
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• 1998

To evaluate the hydraulic resistance behind bodies in a large scale grid numerical model, a drag stress term which is formulated by the drag force is introduced in the depth-integrated Reynolds equations. And also, the applicability and problems of this model are discussed through various numerical experiments where the analytical solutions exist. In the case of a single body, the error range of velocity difference between analytical and numerical solutions is within $\pm$10% and the wake width behind the body shows a good agreement with the analytical solution. When the drag coefficient and the eddy viscosity are precisely decided, the numerical solutions behind a row of bodies will be efficiently used in real situations.

• Journal of Energy Engineering
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• v.27 no.4
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• pp.92-97
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• 2018

This study deals with the numerical analysis for hood development to improve the cooling effect of the engine related components in engine room. Reducing the component temperature in engine room caused by a sudden temperature deviation can minimize the durability degradation of components. Therefore, in this study, numerical analysis for the development of the hood in engine room was carried out in four parts such as generator, battery, ECU and power steel oil which are relatively easy to control temperature among the main components in engine room. In order to verify the numerical analysis, experiments were conducted under the same conditions as those assumed in the numerical analysis.