• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.238-238
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• 2019

산지계곡에는 큰 자갈이나 호박돌이 무더기로 퇴적되어 있어서 대규모 공극을 구성한다. 호우시 이 돌무더기 내부에 빠른 흐름이 형성되고 이에 따른 퇴적사면의 급격한 변동이 발생하기도 한다. 본 연구에서는 대공극 매질의 흐름은 산지계곡에 퇴적된 균일 직경을 가진 구형 입자로 구성된 대규모 공극 매질을 구성하고, 비 Darcy 흐름의 유속에 미치는 입경의 영향을 수리실험으로 조사하였다. 실험에 사용된 구형 입자는 크기가 15.5mm, 25mm, 36.5mm인 유리구슬이고, 조성된 매질의 공극율은 Table 1과 같으며, 실험에서 침투거리는 40cm로 하였다. 실험유량은 0.98~15.41 t/s이고 입자 Reynolds 수는 120~4,580의 범위였다. 동수경사가 증가하면 매질의 단면평균 유속이 비선형적으로 증가하였다. 입경이 작을수록 유속과 동수경사 사이의 비선형적 경향이 더 크다(Fig.1). 동일한 동수경사에서 매질의 입경이 클수록 유속이 빠르게 나타났다.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1469-1473
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• 2004

Non-Darcy흐름에 따른 호안제체의 흐름과 배수갑문을 통한 유출입 특성을 고려한 체절구간의 수리특성분석 도형에 의한 해석결과는 실측자료와 비교적 잘 일치하여 개발된 모형의 적용성이 있음을 보여주었다. 실측치와 비교한 계산결과는 본간(1958) 식에 의한 계산이 나(1987)에 의한 방법보다 비교적 정확하게 계산할 수 있음을 보여주었다. 아울러 완전 또는 불완전 월류의 구분이 없이 잠수도에 의한 계산을 통해서 하나의 유량계수 관계곡선을 사용하여 간편하게 사용할 수 있는 나 식의 사용성을 보여 주었다. 본간 식과 나 식에 의한 계산 값이 실측치보다는 유출입 특성이 크게 나타나고 있는 것으로 나타났다. 따라서 현장에서의 체절구간의 불규칙적인 단면 양상을 감안한 유량계수의 조정이 필요할 것으로 판단된다. 일반적으로 체절구간의 수리특성의 분석을 위해서 제체구간 유량의 고려는 Darcy 흐름에 기초하여 분석한 것이 지금까지의 분석이다. 제체를 통과는 유량과 개방구간을 통과하는 유량의 비가 체절구간이 좁을수록 크게 나타나 제체의 정확한 유출임 특성을 고려한 체절구간의 수리특성을 분석해야할 필요가 있음을 확인하였다.

• Journal of Korea Water Resources Association
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• v.37 no.8
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• pp.613-622
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• 2004

The simulation results of final closing by the developed model considering the flows through tide embankment of non-Darcy and through sluice gate agree well to the observed data which shows the model applicability. In comparative analysis with observed data, the simulation results by Homma(1958) are more accurate than those by Na(1987). The free flow equation with discharge coefficient, regardless of free or submerged flows, by Na based on the submergence ratio is applicable to the engineering practices. Because two simulated discharges are greater than the actual one, the correction of discharge coefficients reflecting the irregular section of actual closing gap situation is necessary. In the hydraulic analysis of final closing, the flow through tide embankment has been generally analysed by Darcy. Hydraulic analysis by the correct discharge through tide embankment of non-Darcy flow is necessary, because the ratio between flows through tide embankment and closing gap is relatively great at final closing.

• Water for future
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• v.24 no.1
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• pp.109-117
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• 1991

The governing equation of flow in porous media is developed on the bases of the continuity equation of fluid for transient flow through a saturated-unsaturated zone, and substitution of Darcy's law. The numerical solutions are obtained by finite element method based on the Galerkin principles weighted residuals. The analysis are carried out by using the unsteady storm data observed and rainfall intensities which are obtained by using the rainfall excess model in considering of the initial losses. The functional relationships between the hydraulic conductivity, capillary pressure head and volumetric water content are applied to the flow of water through unsaturated soil varied with changes of water content.

• Journal of Energy Engineering
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• v.10 no.3
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• pp.266-271
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• 2001

Buoyancy-driven natural convection is analysed by employing a linear stability theory in hori-zontal porous media with net through flow. Darcy's law is used to model the flow characteristics in porous media. Bated on the results of linear stability analysis, a heat transfer correlation was obtained by employing weakly nonlinear analysis. As the net through flow increases, the system becomes more stable and the effect of the Darcy-Rayleigh number on the Nusselt number decreases.

• Journal of Korea Water Resources Association
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• v.53 no.10
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• pp.861-870
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• 2020

As the flow velocity and Reynolds number increase in rockfill porous media, the flow deviates from Darcy conditions. In this study, the permeability tests of rock column specimen and laboratory gabion weir model were carried out to investigate a head loss behaviour of flow through rockfill deposition in small river artificial recharge. Through column test, the nonlinear relationships between flow velocity and hydraulic gradient and coefficients were determined and the correlation formula of hydraulic mean radius and coefficients was proposed. The flow velocities and discharges in voids estimated by proposed equations were well matched with the measured values of laboratory gabion weir model.

• Journal of Korean Society on Water Environment
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• v.23 no.5
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• pp.683-688
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• 2007

Water flow into unsaturated soils is most often modeled by Richards equation consisting of the mass conservation law and Darcy's law. Three standard forms of Richards equation are presented as the head (${\Psi}$)-based form, the moisture content (${\theta}$) based form, and the mixed form. Numerical solutions of these partial differential equations with highly nonlinear terms can cause poor results along with significant mass balance errors. The numerical solution based on the mixed form of Richards equation is known that the mass is perfectly conserved without any additional computational efforts. The aim of this study is to develop fully implicit numerical scheme of Richards equation for one-dimensional vertical unsaturated flow in homogeneous soils using the finite difference approximation, and then to perform sensitivity analysis of infiltration to the variations in the unsaturated soil properties and to different soil types.

• Resources Recycling
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• v.21 no.5
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• pp.38-43
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• 2012

In this study, analysis of the flow of water in the soil environment was attempted to examine the changing patterns of permeability coefficient, k, presented in Darcy's law depending on soil particle size and the pattern of mixed soil that main factor affecting ground water flow in soil environment. In addition, permeability coefficient patterns depending on changes in water temperature and concentration were measured. As a result, the permeability for the soil particle size and mixing pattern is proportional to the size of the particles, and it was also influenced by the porosity depending on the mixed pattern and stratification. Especially compared with the single particle, mixing different sizes samples showed a lower k than the value of smaller single particles. In addition, permeability of groundwater increased with increasing temperature, also permeability decreased depending on the concentration of ions in groundwater. The results of this study were expected to use as meaningful data for the phenomenon reflects the characteristics of the soil to understand mobility of groundwater in soil environment.

• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.9-18
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• 2007

Soil vapor extraction (SVE) is an effective and cost efficient method of removing volatile organic compounds (VOCs) and petroleum hydrocarbons from unsaturated soils. However, soil vapor extraction becomes ineffective in soils with low gas permeability, for example soils with air permeabilities less than 1 Darcy. Incorporating PVDs in an SVE system can extend the effectiveness of SVE to lower permeability soils by shortening the air flow-paths and ultimately expediting contaminant removal. The objective of the research described herein was to effectively incorporate PVDs into a SVE remediation system. The test results show that the gas permeability was evaluated for four different equivalent diameters, increasing the equivalent diameter results in a decrease in the calculated gas permeability. It was found that the porosity for the dry condition was greater than that of the wet condition and will allow flow rate for the same vacuum flow, offering a low resistance to the air flow.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.137-149
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• 2012

Field measurements of resistance to flow are analyzed for 739 rivers vegetated with grass (281 channels), shrubs (150 channels) and trees (308 channels). The measured distribution of Manning roughness coefficients ranges from 0.015~0.250 for grass, 0.016~0.250 for shrubs, 0.018~0.310 for trees. Significant trends are obtained between Darcy-Weisbach (or Manning roughness coefficients) and flow discharge, friction slope, and relative submergence. The regression equations for Darcy-Weisbach and Manning roughness coefficients in vegetated rivers are: $f_{veg}=0.436Q^{-0.363}$, $f_{veg}=3.305S_f^{0.508}$, and $n_{veg}=0.061Q^{-0.124}$, $n_{veg}=0.144S_f^{0.199}$, $V=5.3(h/d_{50})^{1/8.3}{\sqrt{ghS_f}}$, $\sqrt{8/f}(=V/u*)=5.75log(5h/d_{50})$, respectively. These semi-empirical relationships should be useful for hydraulic engineering practice.