• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.221-221
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• 2014

The present work proposes an improved numerical simulator for design and modification of large area capacitively coupled plasma (CCP) processing chamber. CCP, as notoriously well-known, demands the tremendously huge computational cost for carrying out transient analyses in realistic multi-dimensional models, because electron dissociations take place in a much smaller time scale (${\Delta}t{\approx}10-8{\sim}10-10$) than time scale of those happened between neutrals (${\Delta}t{\approx}10-1{\sim}10-3$), due to the rf drive frequencies of external electric field. And also, for spatial discretization of electron flux (Je), exponential scheme such as Scharfetter-Gummel method needs to be used in order to alleviate the numerical stiffness and resolve exponential change of spatial distribution of electron temperature (Te) and electron number density (Ne) in the vicinity of electrodes. Due to such computational intractability, it is prohibited to simulate CCP deposition in a three-dimension within acceptable calculation runtimes (<24 h). Under the situation where process conditions require thickness non-uniformity below 5%, however, detailed flow features of reactive gases induced from three-dimensional geometric effects such as gas distribution through the perforated plates (showerhead) should be considered. Without considering plasma chemistry, we therefore simulated flow, temperature and species fields in three-dimensional geometry first, and then, based on that data, boundary conditions of two-dimensional plasma discharge model are set. In the particular case of SiH4-NH3-N2-He CCP discharge to produce deposition of SiNxHy thin film, a cylindrical showerhead electrode reactor was studied by numerical modeling of mass, momentum and energy transports for charged particles in an axi-symmetric geometry. By solving transport equations of electron and radicals simultaneously, we observed that the way how source gases are consumed in the non-isothermal flow field and such consequences on active species production were outlined as playing the leading parts in the processes. As an example of application of the model for the prediction of the deposited thickness uniformity in a 300 mm wafer plasma processing chamber, the results were compared with the experimentally measured deposition profiles along the radius of the wafer varying inter-electrode gap. The simulation results were in good agreement with experimental data.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.1
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• pp.50-60
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• 2004

An experimental analysis using three-dimensional Laser Doppler Velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.262-273
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• 1991

In the present study, the steady, incompressible, isothermal, developing flow in a 90.deg. rectangular cross sectional strongly curved duct with aspect ratio 1:1.5 and Reynolds number of 9.4*10$^{4}$ has been investigated. Measurements of components of mean velocities, pressures, and corresponding components of the Reynolds stress tensor are obtained with a hot-wire anemometer and pitot tube. In general, flow in a curved duct is characterized by the secondary vortices which are driven mainly by centrifugal force-radial pressure gradient imbalance, and the stress field stabilizing effects near the convex wall and destablizing effects close to the concave wall. It was found that the secondary mean velocities attain values up to 39% of the bulk velocity and are largely responsible for the convections of Reynolds stress in the cross stream plane. Therefor upstream of the bend the Reynolds stress are low. Corresponding to the small boundary layer thickness. At successive planes, large values of Reynolds stress were observed near the concave surface and the side wall.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.12
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• pp.3329-3343
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• 1995

The interaction of mixed convection and surface radiation in a printed circuit board(PCB) is investigated numerically. The electronic equipment is modeled by a two-dimensional channel with three hot blocks. In order to calculate the turbulent flow characteristics, the low Reynolds number k-.epsilon. model which is proposed by Launder and Sharma is applied. The S-4 approximation is used to solve the radiative transfer equation. The effects of the Reynolds number and geometric configuration variation of PCB on the flow and heat transfer characteristics are analyzed. As the results of this study, it is found that the thermal boundary layer occured at adiabatic wall in case with thermal radiation included, and the effect of radiation is also found to be insignificant for high Reynolds numbers. It is found, as well, that the heat transfer increases as the Reynolds number and block space increase and the channel height decreases and the heat transfer of vertical channel is greater than that of horizontal channel.

• Journal of Environmental Science International
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• v.11 no.6
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• pp.497-506
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• 2002

A Photochemical-Trajectory model was used to understand the production of ozone in the atmospheric boundary layer. This model was composed of the trajectory and the photochemical models. To calculate trajectories of air parcels, winds were obtained from the three-dimensional nonhydrostatic mesoscale model (PSU/NCAR MM5V2), and the results were interpolated into constant height surfaces. Numerical integration in the trajectory model was performed by the Runge-Kutta method. The photochemical model consisted of chemical reactions and photodissociation processes. Chemical equations were integrated by the semi-implicit Bulirsch-Stoer method. We performed our experiments from 21 July to 23 July 1994 during the summer time for Seoul area. During the time of maximum ozone concentration in Seoul, four trajectories of air parcels which traveled from Inchon to Seoul were selected. Ozone concentrations estimated by two models are compared with observed one in Seoul area and the photochemical-trajectory model is better fitted than pure photochemical model. During the selected period, high ozone concentrations in Seoul area were more influenced by transferred pollutants from Inchon than emitted pollutants in Seoul.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.2
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• pp.165-173
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• 2008

This study aims at generating automatically three dimensional geometric models of roads using LIDAR data and a digital map. The main processes in the proposed method are (1) generating a polygon encompassing a road region using a road layer from the digital map, (2) extracting LIDAR points within the road region using the polygon, (3) organizing the points into surface patches and grouping the patches into surface clusters, (4) searching the road surface clusters and generating the surface model from the points linked to the clusters, (5) refining the boundary using a digital map. By applying the proposed method to real data, we successfully generated the linear and surface information of the roads.

• Computers and Concrete
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• v.5 no.4
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• pp.279-293
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• 2008

In the present paper a 3D thermo-hygro-mechanical model for concrete is used to study explosive spalling of concrete cover at high temperature. For a given boundary conditions the distribution of moisture, pore pressure, temperature, stresses and strains are calculated by employing a three-dimensional transient finite element analysis. The used thermo-hygro-mechanical model accounts for the interaction between hygral and thermal properties of concrete. Moreover, these properties are coupled with the mechanical properties of concrete, i.e., it is assumed that the mechanical properties (damage) have an effect on distribution of moisture (pore pressure) and temperature. Stresses in concrete are calculated by employing temperature dependent microplane model. To study explosive spalling of concrete cover, a 3D finite element analysis of a concrete slab, which was locally exposed to high temperature, is performed. It is shown that relatively high pore pressure in concrete can cause explosive spalling. The numerical results indicate that the governing parameter that controls spalling is permeability of concrete. It is also shown that possible buckling of a concrete layer in the spalling zone increases the risk for explosive spalling.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.4
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• pp.533-542
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• 2000

Analytical experiments to determine the line-of-sight temperature distribution is conducted by using spectral radiation intensities. For this study, fourteen narrow bands of $25cm^{-1}$ interval in $CO_2\;4.3{\mu}m$ band ($2,050cm^{-1}$ to $2375cm^{-1}$) are selected. The applied system is a one-dimensional gas slab filled with 100% $CO_2$ gas at 1 atm. Two types of temperature profile are tested; parabolic and boundary layer types. Three kinds of radiation calculation are used in the iteration procedure for the temperature inversion; LBL(Line by Line), SNB(Statistical Narrow Band) and WNB(WSGGM. based Narrow Band) models. The LBL solution shows perfect agreement while some error of temperature prediction is caused by radiation modeling error when using SNB and WNB models. The inversion result shows that the WNB model may be used more accurately in spectral remote sensing techniques than the traditional SNB model.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.63-67
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• 2007

The high pressure turbopump carries out supplying the oxidizer in the liquid propulsion rocket in the combustion chamber. Because an LRE requires a very short starting time , the turbine at the turbopump experiences high torque that was produced by the high pressure and the high temperature. The purpose of this study is to evaluate a turbine blade surface temperature profiles at initial starting 0 ${\sim}$ 0.5 sec. Using $Fine^{Tm}$/turbo, three dimensional Baldwin-Lomax turbulence models are used for numerically analysis. The turbine is composed of 108 blades total, but only 7 rotors were considered because of periodic symmetry effect. Because of interaction with a bow shock on the suction surface, the boundary layer separates from suction surface at inner area of turbine blade. The averaged temperature of the turbine blade tip at 1000 rpm is higher than that of 9000 rpm. Especially at 1000 ${\sim}$ 9000 rpm, temperatures increases on the hub side of the turbine blade tip. Moreover at 9000 rpm, the temperatures from the hub to the shroud of the blade tip increase as well.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.4
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• pp.294-304
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• 2003

An experimental analysis using three-dimensional laser Doppler velocimetry(LDV) measurement and computational analysis using the Reynolds stress model in FLUENT are conducted to give a clear understanding of the effect of blade loading on the structure of tip leakage flow in a forward-swept axial-flow fan operating at the maximum efficiency condition ($\Phi$=0.25) and two off-design conditions ($\Phi$=0.21 and 0.30). As the blade loading increases, the onset position of the rolling-up of tip leakage flow moves upstream and the trajectory of tip leakage vortex center is more inclined toward the circumferential direction. Because the casing boundary layer becomes thicker and the mixing between the through-flow and the leakage jet with the different flow direction is enforced, the streamwise vorticity decays more fast with the blade loading increasing. A distinct tip leakage vortex is observed downstream of the blade trailing edge at $\Phi$=0.30, but it is not observed at $\Phi$=0.21 and 0.25.