• 설비공학논문집
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• 제15권4호
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• pp.305-311
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• 2003

DOP aerosol particles with geometric mean diameter of 0.5-3.0 ${\mu}{\textrm}{m}$, geometric standard deviation of 1.1-1.3 and total number concentration of 1,500-8,000 Particles/㎤ were used to determine collection efficiencies of a packed wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. Meanwhile, as for the particle size variation, all of the collection efficiency curves increased rapidly between 0.57-1.41${\mu}{\textrm}{m}$ for the range of water injection rate above 30 L/min. It was also seen that the collection efficiency of a packed wet scrubber is mainly governed by the mechanism of inertial impaction.

• 대한조선학회논문집
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• 제42권6호
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• pp.559-565
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• 2005

As the wave impinges on and overtops the structure, a large highly aerated region is created in front of the structure and water splashs on top of the structure. The broken wave in front of the structure and associated green water on top of the structure are highly aerated containing not only a large number of bubbles but also very large sizes of bubbles. In this paper, the velocity field of the highly aerated region and the splashing water on the top is measured using a modified PIV method incorporating the traditional PIV method with the shadowgraphy technigue by correlating the ' texture ' of the bubble images. The velocity fields of a plunging wave impacting on a structure in a two-dimensional wave flume is measured. It is found that the maximum fluid particle velocity in flout of the structure during the impinging process is about 1.5 times the phase speed of the wave, while the maximum horizontal velocity above the top is less than the phase speed, It is also found that the dam breaking solution does not work well in predicting the green water velocity.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.267-283
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• 2015

The main objective of this study is to investigate experimentally the two-phase flow characteristics in terms of the direct contact condensation of a steam-water stratified flow in a horizontal rectangular channel. Experiments were performed for both air-water and steam-water flows with a cocurrent flow configuration. This work presents the local temperature and velocity distributions in a water layer as well as the interfacial characteristics of both condensing and noncondensing fluid flows. The gas superficial velocity varied from 1.2 m/s to 2.0 m/s for air and from 1.2 m/s to 2.8 m/s for steam under a fixed inlet water superficial velocity of 0.025 m/s. Some advanced measurement methods have been applied to measure the local characteristics of the water layer thickness, temperature, and velocity fields in a horizontal stratified flow. The instantaneous velocity and temperature fields inside the water layer were measured using laser-induced fluorescence and particle image velocimetry, respectively. In addition, the water layer thickness was measured through an ultrasonic method.

• 한국터널지하공간학회 논문집
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• 제6권1호
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• pp.41-50
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• 2004

본 논문에서는 기존댐 인접지에 터널구조물을 건설하기 위한 발파시, 폭괴하중으로 인한 지반진통이 댐 제체와 간극수암에 마치는 영향을 고찰하였다. 댐의 안정성 검토는 발파시 발생하는 코어부의 최대입자속도 (Peak Particle Velocity)를 계산하여 수행하였다. 간극수와 지반진동간의 상호 연계해석을 위하여 댐 제체에 대한 정상상태 흐름해석을 수행하여 간극수압 분포를 파악하고, 유발된 과잉간극수암 및 유효응력분포로 발파하중이 인접지반에 미치는 영향을 분석하였다. 또한 발파와 같은 급속하중 재하 후 과잉간극수압의 증가 및 소산현상 해석을 위하여 Finn & Byrne Model을 적용하여 하중재하 전후의 유효응력 변화양상을 검토하였다.

• 상하수도학회지
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• 제18권1호
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• pp.5-14
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• 2004

A feasibility of using Particle Entrainment Simulator (PES) to evaluate model variables describing sediment entrainment in a river system was investigated. PES in a laboratory was utilized to simulate the sediment resuspension phenomenon in the river and the subsequent relationship between shear rate and sediment entrainment was developed. The total suspended solids (TSS) data from PES was incorporated into statistical models in an effort to describe behaviors of net particle movement in the river. PES was found to be adequate for simulating particle entrainment phenomenon in a river system. Statistical analysis was used to assess propriety of PES data for predictive purposes. The results showed good relationships between PES results and system variables, such as average stream velocity and net particle movement.

• 한국해양공학회지
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• 제25권4호
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• pp.23-27
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• 2011

This experimental study was performed to find rpms of the impeller and the surface flow accelerator to make a uniform velocity vertical distribution in the circular water channel. PIV technique was employed to measure the water velocity profiles into the water depth from the free surface. The number of instantaneous velocity profiles was decomposed into mean and turbulence velocity components, and the distribution of velocity fluctuation and turbulence intensity were computed for each experimental condition. From these results, the velocity uniformity was quantitatively determined to present the flow quality in the measuring section of the circular water channel. It has been shown that the proper operation of the surface flow accelerator would make the uniform velocity profiles and reduce the velocity fluctuation near the free surface.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.213-219
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• 2001

In this paper, particle velocity of slurry flow, a kind of solid-particle two phase flow, was measured by using a particle tracking velocimetry. Particles are modeled by sphere-shaped glass whose diameters are 3mm, 5mm, and 7mm At first, a particle which is falling in the water is captured and analyzed to give their free falling velocity. The falling velocity was very high up to about 4m/sec in the air, which needs special algorithm for the accurate measurement. For the upwelling slurry flow in the straight duct, there are some noises caused by cavity. However, the effect was so small that it does not affect the measurement of large particles. From the preliminary study of applying the PTV to measurement of particle movement in slurry flow, we could find out the optimum value of parameters: threshold value., searching area radius and correlation area size.

• 설비공학논문집
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• 제18권9호
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• pp.745-752
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• 2006

DOS and NaCl aerosol particles were used to determine collection efficiencies of a 2-stage electrostatic wet scrubber with respect to particle size. The DOS and NaCl aerosols have geometric mean diameters of 0.1-3.0 urn, geometric standard deviations of $1.1{\sim}1.8$ and total number concentrations of $450{\sim}2,400\;particles/cm^3$. The tested operating variables for the electrostatic wet scrubber included air velocity and water injection rate. It was shown from the experimental results that particle collection efficiencies increased in the submicron particle size range when different polarities were applied on the water nozzle and corona wire, respectively. This increase in the collection efficiency is attributed to strong electrostatic attraction between the negative water droplets and positive submicron particles. The collection efficiencies also increased when water injection rate was increased or air velocity was decreased. Meanwhile, the pressure drop across the wet scrubber decreased by 90% compared with the existing mechanical wet scrubber. Finally, ammonia gas was used to determine gas removal efficiencies. It was observed that the gas removal efficiencies increased when the air velocity was decreased or the water injection rate was increased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1795-1800
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• 2004

DOS and NaCl aerosol particles with geometric mean diameter of $0.1{\sim}3.0{\mu}m$ geometric standard deviation of $1.1{\sim}1.8$ and total number concentration of $450{\sim}400$ $particles/cm^3$ were used to determine collection efficiencies of a duct-type wet scrubber with respect to particle size. The tested operating variables included air velocity and water injection rate. It was shown from the experimental results that the collection efficiencies increased with increasing water injection rate and decreasing air velocity. It was also seen that the collection efficiency of the Duct-type wet scrubber is mainly governed by the mechanism of inertial impaction.

• 한국대기환경학회지
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• 제23권2호
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• pp.242-249
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• 2007

Deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) were measured at the Chonbuk National University located in Jeonju between June and November 2002. Fluxes of gaseous and particulate PAHs were separately obtained using a water surface sampler (WSS) and a dry deposition plate (DDP). Most of PAHs were deposited in the gaseous form since the low molecular weight PAHs dominates in the atmosphere. The deposition velocity of particulate PAHs was higher than that of gaseous PAHs when the molecular weight was low, but substantially decreased as the fine particle fraction increased with molecular weight. The deposition velocity was generally higher at high wind speeds. However, increase in the deposition velocity in unstable atmospheric conditions was also observed for gaseous PAHs of intermediate molecular weight.