• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.147-152
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• 1992

본 연구에서는 같은 직경의 2개 원형구멍이 동축상에 있는 4변고정, 등반성 정사각형판의 자유진동특성을 충격진동실험과 유한요소 해서방법으로 원형 구멍직경의 변화에 다른 고유진동수와 무차원 진동수 매개변수를 구하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.180-185
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• 2013

A new formulation of the MNDIF method is introduced to extract highly accurate natural frequencies of concave plates with arbitrary shape. Originally, the MNDIF method cannot yield accurate natural frequencies for concave plates. To overcome this weak point, a new approach of dividing a concave plate into two convex domains is proposed and the validity and accuracy is shown in a verification example.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1608-1613
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• 2007

최근들어 수자원 분야에서 GIS(Geographic Information System)의 활용에 대한 많은 연구가 이루어지고 있다. 수자원 관련 분야에 있어서 GIS는 수문현상에 영향을 미치는 기상학적인 요인, 토양, 토지이용도, 배수 유역의 형태 등 수문정보를 획득하기 위한 수단으로 사용될 수 있을 뿐만 아니라, 유역에서의 지형학적, 기후학적 특성을 시간과 인력을 절약하여 정량화할 수 있다는 것이 입증되고 있다. 하천에서의 유출량 추정은 강우, 수위와 같은 수문데이터의 신뢰도에서 많은 문제점이 야기되고 있다. 따라서 모의 입력매개변수의 중요요소인 지형정보의 경우 GIS 기법을 이용할 경우 기존 방법과는 달리 신뢰성 있는 정보를 획득할 수 있으므로 모형의 결과를 개선하는 데 도움이 될 것이다. 본 연구에서는 미국의 Environmental Modeling Research Laboratory(EMRL)에서 개발한 지리정보시스템과 수문유출모형이 접목된 WMS(Watershed Modelling System) 모형을 HEC-1 모형과 연계하여 낙동강수계 제1지류인 회천유역 개진1, 개진2 지점의 유출 해석을 실시하였다. GIS와 결합된 홍수유출모형인 WMS를 이용하여 유역 내의 지형특성인자 및 하천망을 추출하였으며, 유출해석은 WMS에 내재된 HEC-1을 이용하였다. 유효강우량의 산정을 위해 SCS CN 값을 사용하였으며, CN 계산을 위해서는 토지이용도 토양도를 이용하였다. 합성단위도법은 SCS 무차원 단위도법을 사용하여 유출을 모의하였다.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.833-840
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• 2007

The experimental study was carried out to investigate propagation distance of flood wave due to levee breach in a flat inundation area without obstacle. Hitter solution was considered to formulate the experimental results and a representative form was written referring to existing researches. As a result of experiments, it was found that the propagation velocity of the wave front in inundation area was significantly influenced by the initial water level in a channel, which was similar to flow in a channel due to dam break. An empirical formula was also suggested using the experimental results. The dimensionless propagation distance L can be written as the power function of dimensionless time T Coefficients k and m were varied with the dimensionless time T whereas k and m in Ritter solution were 2 and 0, respectively. The variation of coefficients in the relationship between L and T was influenced by the water depth in the inundation area and the fact proved that the changing points of L in the slope of relationship between L and T are the same to those of relationship between the dimensionless maximum water depth in the inundation area, $h_{max}$ and L.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.3
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• pp.75-80
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• 2019

The article is devoted to the interpretation of ammonia, one of the fine dust precursors, absorption behavior in water turbulent flow. The water flow was considered as a turbulent flow with Reynolds number more than $10^4$, because ammonia gas penetration depth was deeper at turbulent flow compared to laminar flow. For the interpretation, the dimensionless mass transfer governing-equation and the constant physical-properties at room temperature were used. The diffusivity of ammonia in water and the kinematic viscosity of water were $2{\times}10^{-9}m^2/s$ and $1{\times}10^{-6}m^2/s$, respectively. The concentration distribution of ammonia in water was estimated with respect to the position from the point where the water started to be exposed to ammonia. The quantitative distribution as a function of the mixing length was also acquired. The quantitative interpretation may provide the insight how much the turbulent flow was more efficient to remove ammonia rather than the laminar flow.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.3
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• pp.225-240
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• 2006

In order to calculate bending moments of rectangular plates with three edges clamped the other free subjected to both a uniform load and a triangular load, a finite difference equation for the non-dimensional governing equation are presented and numerical solutions with different aspect ratios and/or number of grid points are analyzed. The finite difference solutions are obtained by use of grid points up to 11,520 and the optimum grid points according to aspect ratios of the plate are presented as well. The obtained numerical solutions are shown to satisfy the given x moment boundary condition at the free edge, which can not be satisfied in Levy's analytical solutions and peculiar behaviour of the calculated moments is observed around the corners between the free edge and fixed ones. The numerical solutions of bending moments subjected to both a uniform load and a triangular load are compared with the corresponding analytical solutions which are shown in very good agreement on the solution domain except the neighborhood of the free edge.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.720-726
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• 2009

Hydrodynamic similarity was investigated in pressurized three-phase slurry bubble columns by selecting the bubble holdup and pressure drop as objective functions, for the effective design and scale-up of it. In addition, effects of operating variables on the bubble holdup with variation of column diameter were also analyzed. Gas velocity($U_G$), viscosity(${\mu}_{SL,eff}$) and surface tension(${\rho}_{SL}$) of slurry phase, density difference between the slurry and gas phases(${\rho}_{SL}-{\rho}_G$) depending on the operating pressure, pressure drop per unit length(${\Delta}P/L$), column diameter(D) and gravitational acceleration(g) were chosen as governing parameters in determining the bubble holdup and pressure drop in the column. From the dimensional analysis, four kinds of dimensionless groups were derived from the 7 parameters and 4 fundamental dimensions. Effects of dimensionless groups such as Reynolds, Froude and Weber numbers on the bubble holdup in the column were discussed. The pressure drop and bubble holdup could be predicted from the correlation of dimensionless groups effectively, which could be used as useful information for the design and scale-up of pressurized slurry bubble columns.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.6
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• pp.38-46
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• 2011

In order to simulate the ignition-gas injection in the interior ballistics, a two-dimensional analytic code for two-phase flows has been developed. The Eulerian-Lagrangian approach and the low-dissipation simple high-resolution upwind scheme(LSHUS) have been adopted in the numerical code for the propellant combustion of the gun propelling charges. The ghost-cell extrapolation method has been used for the moving boundary in the chamber with the projectile movement. The calculation results of the developed code have been compared and verified through those of the dimensionless IBHVG2 code and the previous one-dimensional code. In comparison with the two-phase flows according to the drag models, the numerical analysis of the muzzle velocity has been affected by the drag model.

• Journal of Soil and Groundwater Environment
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• v.12 no.4
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• pp.1-7
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• 2007

Slug/bail tests were conducted in sand layer (sbt-1 well), silty sand layer (sbt-2 well), and mixed sand and silty sand layer (sbt-3 well). Hydraulic conductivity and specific storage coefficient were estimated through slug/bail tests. Pore volumes of groundwater level drawdown zone for bail test were estimated by using hydraulic conductivity and specific storage coefficient. KGS model was most suitable interpretation method of slug/bail tests. Average hydraulic conductivity for slug/bail tests were estimated to be $6.65{\times}10^{-5}$ m/sec in sbt-1 well, $6.33{\times}10^{-6}$ m/sec in sbt-2 well, and $3.72{\times}10^{-5}$ m/sec in sbt-3 well. Average specific storage coefficient for slug/bail tests were estimated to be 0.0225 in sbt-1 well, 0.0177 in sbt-2 well, and 0.0259 in sbt-3 well. Dimensionless time and dimensionless wellbore storage were estimated by use of transmissivity, storativity, test time, and specification of test wells. And, dimensionless drawdown were selected by parameter ${\alpha}\;and\;{\beta}$ parameter from Cooper et al. (1967). Radius of influence were estimated by estimated dimensionless time, dimensionless wellbore storage, and dimensionless drawdown. The average radius of influnce for slug/bail tests were estimated to be 1.377 m in sbt-1 well, 1.253 m in sbt-2 well, and 1.558 m in sbt-3 well. Pore volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,636cm^3$ in sbt-1 well, $71,561cm^3$ in sbt-2 well, and $100,418cm^3$ in sbt-3 well. Pore volume excepted well volume at groundwater level drawdown zone by dummy withdrawal for bail tests were estimated to be $145,410cm^3$ in sbt-1 well, $71,353cm^3$ in sbt-2 well, and $100,192cm^3$ in sbt-3 well.

• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.35-41
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• 2020

The immobilization of the hydroxylamine-oxidoreductase on the water channel surface was performed to investigate the efficacy of ammonia removal in turbulent flow. The reaction by this enzyme proceeds rapidly by converting hydroxylamine into nitrous acid. For the analysis of the effect, a dimensionless mass transfer governing equation was established with the physical properties based on room temperature. The ammonia diffusion coefficient in water and the kinematic viscosity coefficient of water were 2.45×10-9 ㎡/s and 1×10-6 ㎡/s, respectively. The distribution of ammonia concentration in the water was calculated with respect to the distance from the point at which exposure to ammonia began. The quantitative distribution with respect to the mixing depth was also found. Such a quantitative analysis can provide insight into whether the enzyme immobilized on the water channel surface can be effectively used for ammonia removal.