• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1998년도 학술발표회 논문집
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• pp.632-637
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• 1998

The purpose of this study of this study is to find tide and tidal current variation by three dimensional numerical model of tide and tidal current in the bay of Cheonsu in Korea. On the basis of the observed data on water temperature and salinity data and wind data of summer(July) in the bay of Cheonsu in Korea, water circulation in the bay of Cheonsu is investigated with use of a robust diagnostic numerical model, including calculated co-range and co-tidal charts of M2 tide are similar to the observed ones. The residual flow Pattern at the surface layer during summer formed clockwise circulation in the front coastal the dike of the Sosam A zone(Ganwor island) and Taeju island. The residual flow pattern at the 15m layer during formed clockwise circulation in the front Taeju island. The residual flow Pattern at the surface layer formed anti-clockwise circulation in the upper Sangmok and Naepasu island.

• 대한기계학회논문집B
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• 제29권3호
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• pp.376-383
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• 2005

In the paper we investigate characteristics of a transitional behavior from a premixed flame to a triple flame in a lifted flame according to the change of equivalence ratio. In previous study, we showed that the stabilized laminar lifted flame regime is categorized by regimes of premixed flame, triple flame and critical flame. A gas-chromatograph is used to measure concentration field, a smoke-wire system is used to measure streak line, and a PIV system is used to measure velocity field in lifted flame. In the visualization experiment of smoke wire, the flow divergence and redirection reappeared in premixed flame as well as triple flame. Thus we cannot express the flame front of lifted flame has a behavior of triple flame with only flow divergence and redirection. In PIV measurement, flow velocity for those three flames has minimum value at the tip of flame front. To differentiate triple flame and premixed flame, $\Phi$ value of partially premixed fraction is employed. The partially premixed fraction $\Phi$ was constant in premixed flame. In critical flame small gradient appears over the whole regime. In triple flame, typical diffusion flame shape is obtained as parabolic distribution type due to diffusion flame trailing.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.103-110
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• 2004

The major trend in global automotive market is changing drastically in the way that a vehicle FECPS(Front End Cooling Pack System) is designed and manufactured as an assembly part. The system can encompass many functions, be assembled into a vehicle as a module, and reduce the production cost as well as time. The FECPS consists of an impact beam, an aluminum condenser and a radiator, a carrier and a cooling fan with a BLDC motor. In order to predict the performance of a FECPS accurately, it is essential to properly model the air flow field through various heat exchangers, such as a condenser or a radiator. In this study, the flow field of the system is measured by a PIV(Particle Image Velocimetry) system. The result is compared with that measured with multi-channel anemometer.

• 설비공학논문집
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• 제13권9호
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• pp.904-913
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• 2001

The objective of this study was to investigate the characteristics of jet flow and heat transfer caused by trapezoid rods array in impinging jet system. In this study, trapezoid rods have been set up in front of flat plate to serve as a turbulence promoter. The bottom width of trapezoid rod was W=4, 8 mm and oblique angle were 80$^{\circ}$. The space from rods to the heating surface was C=1, 2, 4 mm, the pitch between each rods was P=30, 40, 50 mm, and the distance from nozzle exit to flat plate was H=100, 500 mm. This results were compared with the case without trapezoid rods. As a result, when rods are installed in front of the impinging plate, the acceleration of the jet flow and the eddies due to the rods seem to contribute to the heat transfer enhancement. Among test conditions, the heat transfer performance was best for the condition of W=8 mm, C=1 mm, P=30 mm and H/B=10. The maximum heat transfer rate is about 1.9 times larger than that without trapezoid rods.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.275-278
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• 2005

This study has focused on manufacturing technique of powder injection molding of watch case which made from zirconia powder. A series of computer simulation process was applied to prediction of the flow pattern in the inside of the mould and defects as weld line. The material properties of melted feedstock inclusive of the PVT graph and thermal viscosity flowage properties were measured for obtaining the input data in computer simulation. Also, molding experiment was conducted and the results of experiment showed that good agreement with simulation results far flow pattern and weld line location. On the other hand, gravity and inertia effect have an influence on velocity of melt front because of high density of ceramic powder particles in powder injection molding against the polymer injection molding process. In the experiment, the position of melt front was compared with upper gate and lower gate position. The gravity and inertia effect could be confirmed in the experimental results.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.586-591
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• 1996

Through the analysis of many experimental post-dryout data, it is shown that the most probable flow regime near dryout or quench front is not annular flow but churn-turbulent flow when the mass flux is low. A correlation describing the initial droplet size just after the CHF position at low mass flux is suggested through regression analysis. In the post-dryout region at low pressure and low flow, it is found that the suggested one-dimensional mechanistic model is not applicable when the vapor superficial velocity is very low, i.e., when the flow is bubbly or slug flow regime. This is explained by the change of main entrainment mechanism with the change of flow regime. Therefore, the suggested correlation is valid only in the churn-turbulent flow regime ( $j_{g}$ $^{*}$＝0.5~4.5).).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1789-1794
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• 2004

The present study investigates flow characteristics in an optical disc drive. Detailed knowledge of the flow characteristics is essential to analyze flow-induced noise and vibration, forced convection and flow friction loss. The ODD used in the personal computer is used for the experiment and rotating velocity of disc is under the 4500 rpm. Time-resolved velocity components and velocity spectrum are obtained using the laser Doppler anemometry (LDA). The results show that the front holes reduce now-induced noise and the position of pickup body affects flow near the window. In addition, il is possible for cooling of heat sources in an optical disc drive through measuring the flow fields under the tray.

• 한국유체기계학회 논문집
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• 제13권4호
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• pp.25-30
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• 2010

Flow analysis and performa nce evaluation have been performed for a ventilation axial-flow fan with different positions of the motor. Two different positions of motor have been tested; one is in front of the impeller and the other is behind the impeller. Flow analyses are performed by solving three-dimensional Reynolds-averaged Navier-Stokes equations through a finite-volume solver. Preliminary numerical calculations are carried out to test the performances of different turbulence models, i.e., SST model, k-$\omega$ model, and k-$\varepsilon$ model with and without using empirical wall function in the flow analysis. The validation of numerical analyses has been performed in comparison with the experimental data. The numerical results for the performance characteristics of the ventilation axial-flow fan with two different positions of the motor have been presented.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2004년도 제29회 KOSCI SYMPOSIUM 논문집
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• pp.55-61
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• 2004

Leading front of a lifted diffusion flame in turbulent mixing layer was investigated in order to find a appropriate definition of the turbulent edge propagation speed. The turbulent lifted diffusion flame was simulated by employing the flame hole dynamics combined with level-set method which yields a temporally evolving turbulent extinction process. By tracing the leading front locations of the temporal flame edges, temporal variations of the liftoff height, local flow velocity, and edge propagation speed at the leading front were investigated and they demonstrated the flame-stabilization condition of the turbulent lifted flame. Finally, a turbulent edge propagation speed was defined and its temporal variation from the simulation was discussed.

• 한국자동차공학회논문집
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• 제20권6호
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• pp.67-72
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• 2012

Novel Front End Module(FEM) with improved pedestrian protection is very important to reduce the severity of pedestrian injury. The FEM needs to have enough space from hood to absorb the energy from any pedestrian collision. In this study, the cooling performance of the FEM to cool the engine was investigated under 25% height reduction. The results indicated that the cooling performance analysis was about 86% level compared to that of the conventional FEM. Also, good qualitative agreement between CFD predictions and experimental measurements was found. This FEM needs the cooling performance enhancement for changed air flow path at the frontal part of vehicle. Therefore, we showed an improved performance using air guide setup and shape modification under the high load condition.