• 한국분무공학회지
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• 제22권4호
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• pp.175-184
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• 2017

The numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of $L{\times}W{\times}H=1.5{\times}1.5{\times}2.0m^3$ and a water mist nozzle that be installed 1.8 m from fire pool. In the present study, the parameters of nozzle for simulation are the droplet size and the spray velocity. The droplet size influences to fire flume on fire suppression more than the spray velocity because of the effect of the terminal velocity. The optimal condition for fire suppression is that the droplet size and the spray velocity are $100{\mu}m$ and 20 m/s respectively.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1988년도 제30회 수공학연구발표회논문초록집
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• pp.29-36
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• 1988

A general scheme is developed which determines the Lagrangian motions of water particles by the Eulerian velocity at their mean positions by use of Taylor's theorem. Utilizing the Stokes finite-amplitude wave theory, the mass transport velocity which includes the effects of higher-order wave components is determined. The fifth-order theory predicts the mass transport velocity less than that given by the existing second-order theory over the whole depth. Limited experimental data for changes in wave celerity in closed wave flumes are compared with the theoretical predictions.

• 한국안전학회지
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• 제11권4호
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• pp.24-28
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• 1996

The speckle photography technique is one of the novelest velocity measurement methods. This study examines the possibility that this technique will become practically applicable. In this study, LSP is applied to the fine water mist spray. Moreover, a He-Ne gas laser is employed as the light source in order to enhance the validity of this technique. It becomes clear that this technique using a He-Ne gas laser can obtain a whole instantaneous two-dimensional velocity distribution and also apply to test the performance of fine water spray.

• 한국가시화정보학회지
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• 제6권2호
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• pp.28-32
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• 2008

Contrary to the flow rate in fully filled pipe flows, the flow rate in partially filled pipe flows is significantly influenced by the variation of water level, channel slop, and so on. The major difference in these two flows results from the existence of a free surface. To make it clear, in the present study, a similarity of the velocity profile in a partially filled circular pipe has been investigated according to the water level. A particle image velocimetry (PIV) technique was applied to measure the three-dimensional velocity profiles. As a result, there is found a similarity of the velocity profile near the central region. However, near the side wall, the similarity is broken due to the interaction between the wall and the free surface.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.73-77
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• 2006

Flow rate measurement is one of the difficult problems in the industrial applications. Especially, flow rate in a partially filled pipeline is affected by many parameters such as water level, channel slop, etc. In the present study, prior to the development of a flowmeter, the flow characteristics has been investigated by particle image velocimetry (PIV) measurements. Three-dimensional velocity distributions were obtained from sectional measurements of velocity profiles according to the water level. As a result, it is found that there is no similarity in the velocity profile when the lateral position is changed. In addition, the maximum velocity does not always occur on the free surface. It depends on the water level. In the aspect of flow rate measurement, the previous calculus based upon point measurement techniques is proved to be inaccurate because of the lack of whole flow information.

• 환경영향평가
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• 제20권1호
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• pp.37-48
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• 2011

Recently, the social and environmental functions of nature river are important due to the increase of expectation for river restoration. So it should be considered the effect of vegetation affecting the conveyance capacity and hydraulic resistance. However, it has not yet proposed a objective standard and modeling method to estimate the effect of conveyance capacity according to vegetaion distribution in the watercourse such as water level or velocity. Therefore, this study simulates the variations of water level and velocity using 3-dimensional hydrodynamic model, EFDC, to consider a conveyance capacity in downstream of the Soyang Reservoir. The simulation results were validated using statistical index such as F-test and T-test. As results, the water level rises about 0.01 to 0.47m and velocity difference are about -0.95m/s to 0.23m/s.

• 한국산업융합학회 논문집
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• 제9권3호
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• pp.229-233
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• 2006

The water vapor permeability of polypropylene spun bond non-woven fabrics were investigated with the water vapor permeability velocity at $20^{\circ}C$, $30^{\circ}C$ and $40^{\circ}C$ by applying the hygroscopic method. At each temperature 50, 65 and 80 %RH conditions were used. The results indicated that the water vapor permeability velocity increased with increasing the water vapor concentration difference between both sides of sample surfaces and it decreased with increasing the number of the piled-up fabrics and the apparent density.

• 상하수도학회지
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• 제20권1호
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• pp.156-163
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• 2006

While sludge is settling in batch column, sludge concentration becomes high. Because the characteristic of sludge settling changes in function of time due to the sludge concentration change, the sludge settling velocity changes too. Also, because the sludge settling characteristic is influenced by a physical characteristic of sludge and a column height etc, it is difficult to exactly measure the sludge settling characteristic. Although the sludge volume indexes, SVI, SSVI and $SSVI_{3.5}$, are used to predict sludge settling characteristic, these indexes are not reliable values. Because the previously established models for sludge settling velocity predict the sludge settling velocity only, it is difficult to predict sluge-water interface height by using those models. The purpose of this experiment is to establish the empirical model which predicts the sludge interface height change with respect to the sludge physical characteristic and the settling condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.49-54
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• 2003

Scale is formed when hard water is heated or cooled in heat transfer equipments such as heat exchangers, condensers, evaporators, cooling towers, boilers, and pipe walls. When scale deposits in a heat exchanging surface, it is traditionally called fouling. The objective of the present study was to compare the fouling characteristics of river and tap water in a heat exchanging model. FromtheSEM analyses for tap water the $calciteformofCaCO3_{3}$ was formed. For river water, however, the $aragoniteCaCO_{3}$ wasformed.In order to investigate velocity effects on the fouling characteristics in the heat exchanging model, the inlet velocity was varied with 0.5, 1.0 and 1.5 m/s, respectively. The fouling characteristics of river water were quite different from those of tap water. For the case of the 'velocity of 1.5m/s', the overall heat transfer coefficient was reduced up to 26% than that of the 'velocity of 0.5m/s'

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.117-118
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• 2005