• 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.

• The Journal of the Acoustical Society of Korea
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• v.30 no.7
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• pp.402-407
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• 2011

The necessary and sufficient condition for causality of a physical system can be expressed as Kramers-Kr$\ddot{o}$nig (K-K) relation. K-K relation for acoustic wave is a Hilbert transforms pair between dispersion equations of phase speed and attenuation. In this study, we quantitatively compare the acoustic measurements in water-saturated glass beads for the frequency ranges from 400 kHz to 1.1 MHz with the predictions of differential form of K-K relation obtained by Waters et al. For media with attenuation obeying an arbitrary frequency power law, acoustic measurements show good agreements with the predictions of Kramers-Kr$\ddot{o}$nig relation.

• The Korean Journal of Rheology
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• v.3 no.2
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• pp.117-123
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• 1991

현탁액에 대한 기본적인 유변학적 특성을 조사하기 위해 입자의 부피분율에 따른 점도의 변화를 측정하였고 현탁액의 Die Swell 현상에 대해 실험적으로 규명하였다. 뉴톤성 특성을 조사하기 위해 입자의 부피 분율에 따른 점도의 변화를 측정하였고 현탁액의 Die Swell 현상에 대해 실험적으로 규명하였다. 뉴톤성 특성을 갖는 Silicone 오일을 현탁 매질 로 사용하였고 미세한 유리 구슬이 filler로써 사용되었다. 현탁액의 점도는 Couette 점도계 와 모세관 점도계를 사용하였다. 관의 입구와 출구에 대한 보정을 위해서 Bagley의 방법을 이용하였으며 중력으로 인한 Swell의 감소효과를 제거하기 위해서 분사 유체와 유사한 밀 도를 지니며 분사 유체와 섞이지 않는 유체를 담은 부력용기가 사용되었다. Die Swell 현상 은 사진을 찍고 이를 정밀한 확대경을 통해 관찰함으로써 수치적으로 값을 얻었다.

• Journal of Soil and Groundwater Environment
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• v.6 no.2
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• pp.3-13
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• 2001

It has been known that nonlinear characteristics of sorption affect the transport behavior of water soluble pollutants in soils. However detailed experimental studies have not been performed to verify the effect of non-linearity of adsorption isotherm on transport of chemicals in porous media. In this research, the distortion of breakthrough curves of a cationic surfactant (cetylpyridinium chloride, CPC) in a engineered stainless steel column packed with glass beads were investigated. Glass beads with about 110 $\mu\textrm{m}$diameter coated with a thin n-decane film were used as the media providing the sorption surface for CPC. The CPC adsorption isotherm on the surface of n-decane from aqueous solution was a typical Langmuir type. The breakthrough curve of CPC using step Input showed a late breakthrough on the front side and early breakthrough on the back side accordance to the shape of the isotherm. The retardation factor of CPC was found to be a strong function of the input concentration, which also a manifestation of the non-linearity of the isotherm. The retardation factors for the CPC with step input agreed with those of pulse input that the maximum concentrations are controlled to be the same as the step input concentrations. This results support the validity of the unproven field practices of using hydrogeotracers with non-linear adsorption isotherms to determine the hydrogeological parameters, e.g., NAPL saturation, air-water or NAPL-water interfacial areas.

• The Journal of the Acoustical Society of Korea
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• v.25 no.5
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• pp.246-256
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• 2006

The plane wave reflection coefficient is an acoustic property containing all the information concerning the ocean bottom and can be used as an input parameter to various acoustic propagation models. In this paper, we measure the plane wave reflection coefficient, the sound speed, thd the attenuation for saturated granular medium in the water tank. Three kinds of glass beads and natural sand are used as the granular medium. The reflection experiment is performed with the sinusoidal tone bursts of 100 kHz at incident angles from 28 to 53 degrees, and the sound speed and attenuation experiment are performed also with the same signal. From the measured reflection signal, the reflection coefficient is calculated with the self calibration method and the experimental uncertainties are discussed. The sound speed and the attenuation measurements are used for the estimation of the porosity and permeability, the main Biot parameters. The estimated values are compared to the directly measured values and used as input values to the Biot theory in order to calculate the theoretical reflection coefficient. Finally, the reflection coefficient predicted by Biot theory is compared to the measured reflection coefficient and their characteristics are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.45-53
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• 1987

The purpose of this research was to study the kinetics of a packed bed aerobic biofilm process. Experiments were carried out by feeding an aerated packed bed reactor with a synthetic wastewater. The reactor packed with glass beads as media had a nominal hydraulic detention time of 5 hours. The flow pattern in the reactor was determined by a tracer test using a NaCl solution to be a completely-mixed type. The results of the research showed that the F/M ratio in the reactor was almost constant since the the biomass increased due to the growth of biofilm as the volumetric organic loading increased. It was also proved theoretically and experimentally that packed bed aerobic biofilm process could be analyzed by the kinetics of completely-mixed activated sludge process with sludge recycle.