• 농업과학연구
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• 제38권2호
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• pp.331-341
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• 2011

To provide variation of water supply for instream flow from reservoirs with various magnifications of paddy irrigation area to watershed area, 8 reservoirs were selected to draw operation rule curve and to analyze water supplies from reservoirs. Reliability of 90% for supplying irrigation water from reservoir was able to maintain and instream flow water was able to be supplied only in the reservoir with magnification of paddy irrigation area to watershed area above 3. The more magnification of paddy irrigation area to watershed area increased, the more ratio of irrigation water to total water storage decreased, and the more ratio of instream flow water to total water storage increased. From the heightening 113 reservoirs in Korea, annual irrigation water was estimated to 1,146.05 $Mm^3$ in normal operation, 839.57 $Mm^3$ in withdrawal limited operation, and annual instream flow water was estimated to 149.68 $Mm^3$ in normal operation, 283.19 $Mm^3$ in withdrawal limited operation. It was concluded that withdrawal limited operation was followed to have the premise of saving irrigation water, more instream flow water was able to be supplied from reservoirs with high magnification of paddy irrigation area to watershed area.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.584-585
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• 2010

A numerical simulation was performed to investigate the internal flow characteristics in gas turbine nozzle by the variation of flow area of the nozzle. In general the area of turbine nozzle is chosen by the most substantial factor on performance improvement of turbine at the first stage. In the performances test through CFD analysis for three types of nozzle with conventional, enlarged and reduced area, reduced one with effective flow area (EFA) was the most efficient. That is the minimum effective value within EFA limit defined by the manual of technical order had a good performance. It is useful to avoid the low power problem in the test of performance after maintenance and overhaul of turbine engine.

• 신재생에너지
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• 제3권3호
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• pp.14-19
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• 2007

A flow channel model of a bipolar plate with varying cross-sectional area was newly designed for improving performance and efficiency of a PEM fuel cell stack. As a result, the varying cross-sectional area model showed poor uniformity in velocity distribution, however, maximum velocity in the flow path is about 30% faster than that of the uniform cross-sectional area model. The proposed varying cross-sectional area model is expected to diffuse operating fluids more easily into diffusion layer because it has relatively higher values in pressure distribution compared with other flow channel models. It is expected that the implementation of the varying cross-sectional area model can reduce not only the mass transport loss but also the activation loss in a PEM fuel cell, and open circuit voltage of a fuel cell can thus be increased slightly.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.591-596
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. Two models are examined: a planar two-dimensional channel, and an axisymmetric tube. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and compared to existing experimental data. Computational results for an axisymmetric tube show that as cross-sectional area falls with a reduction in downstream pressure, flow rate increases and reaches a maximum when the speed index (mean velocity divided by wave speed) is near unity at the point of minimum cross-section area, indicative of wave speed flow limitation or "choking" (flow speed equals wave speed) in previous one-dimensional studies. For further reductions in downstream pressure, flow rate decreases. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is ${\le}$ 2 the area throat is located near the downstream end; as wall taper is increased to ${\ge}$ 3 the constriction moves to the upstream end of the tube. In the planar two-dimensional channel, area reduction and flow limitation are also observed when outlet pressure is decreased. In contrast to the axisymmetric case, however, the elastic wall in the two-dimensional channel forms a smooth concave surface with the area throat located near the mid-point of the elastic wall. Though flow rate reaches a maximum and then falls, the flow does not appear to be choked.

• Nuclear Engineering and Technology
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• 제37권6호
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• pp.525-536
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• 2005

The interfacial area transport equation dynamically models the changes in interfacial structures along the flow field by mechanistically modeling the creation and destruction of dispersed phase. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport mechanism for various sizes of bubbles, the transport equation is formulated for two characteristic groups of bubbles. The group 1 equation describes the transport of small-dispersed bubbles, whereas the group 2 equation describes the transport of large cap, slug or chum-turbulent bubbles. To evaluate the feasibility and reliability of interfacial area transport equation available at present, it is benchmarked by an extensive database established in various two-phase flow configurations spanning from bubbly to chum-turbulent flow regimes. The geometrical effect in interfacial area transport is examined by the data acquired in vertical fir-water two-phase flow through round pipes of various sizes and a confined flow duct, and by those acquired In vertical co-current downward air-water two-phase flow through round pipes of two different sizes.

• 설비공학논문집
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• 제25권6호
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• pp.317-323
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• 2013

A multi-perforated tube indicates the existence of multiple holes of various shapes on the surface of a long cylinder-type or rectangular tube, and a hole installed on the surface is called an orifice, as it is relatively small in size, compared with the surface area of the tube. In this study, the flow characteristics of a circular multi-perforated tube with many orifices on the surface were investigated experimentally and numerically. The volume flowrate issuing from each orifice, discharge angle, effective flow area ratio, and the flow fields around the orifices were measured and visualized, with the variation of the orifice area ratio, at the same blockage ratio. The volume flowrate distributions along the flow direction of the multi-perforated tube tends to be more uniform, as larger orifices were positioned at the inlet side of the multi-perforated tube, compared with no orifice area change along the flow direction.

• 한국환경보건학회지
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• 제31권1호
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• pp.1-6
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• 2005

This study was conducted to identify the runoff characteristics of non-point source according to rainfall in Nam watershed. Land-uses of the Nam watershed were surveyed paddy field 4.5%, crop field 6.8%, mountainous 78.7%, urban 2.4%, and etc. 7.7%. Mean runoff coefficients in each area were observed Ⅰ area 0.08, Ⅱ area 0.08, and Ⅲ area 0.05. In the relationship between the rainfall and peak-flow, correlation coefficients(r) were investigated Ⅰ area -0.8609, Ⅱ area 0.6035, and Ⅲ area -0.4913. In the relationship between the antecedent dry period and first flow runoff, correlation coefficients(r) were investigated Ⅰ area -0.9093, Ⅱ area -0.1039, and Ⅲ area -0.7317. The discharge of pollutant concentrations relates to the flow rate of storm-water. In the relationship between the rainfall and watershed loading, exponent values of BOD, COD, SS, and T-N were estimated to 1.2751, 1.2003, 1.3744, and 1.1262, respectively.

• 한국환경과학회지
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• 제15권10호
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• pp.967-973
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• 2006

In this study used tank model and specific discharge to calculate low-flow of mountain basin and supply data that need in water resources plan. Low-flow is calculated byspecific discharge and area ratio method as resulted that calculate storage of low-flow by tank model was construed that showd all similar aspect. In judged to help in water resources plan establishment calculating low-flow using model to supplement uncertainty of observed data in that calculate of low-flow ungaged mountain area. It shows by economical and realistic plan until 12 years after development that run parallel and use economic performance analysis result valley flow and groundwater. But wide area water services and Chungju dam since 12 years onward was expose that is economic.

• 한국항해학회지
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• 제12권1호
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• pp.85-112
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• 1988

From the point of view of safety of life and property at sea and the protection of the marine environment, the Vessel Traffic Management System along the Korea coastal waterway is inevitably introduced. But the establishing priority per area must be evaluated under the restricted budget. In this case, the estimated traffic flow has a major effect on priority evaluation. In the former paper , an algorithm was proposed for estimating the trip distribution between each pair of zones such as harbours and straits. This paper aims to formulate a simulation model for estimating the dynamic traffic flow per area in the Korea coastal waterway. The model consists of the algorithm constrined by the statistical movement of ships and the observed data, the regression analysis and the traffic network evaluations. The processed results of traffic flow except fishing vessel are summarized as follows ; 1) In 2000, the traffic congestions per area are estimated, in proportion of ship's number (tonnage), as Busan area 22.3%(44.5%), Yeosu area 19.8%(11.2%), Wando-Jeju area18.1%(6.8%), Mokpo area 14.9%(9.9%), Gunsan area 9.1%(9.3%), Inchon area 8.1%(7.7%), Pohang area 5.5%(8.5%), and Donghae area 2.2%(2.1%). 2) For example in Busan area, the increment of traffic volume per annum is estimated 4, 102 ships (23 million tons) and the traffic flow in 2000 is evaluated 158, 793 ships (687 million tons). 3) consequently, the increment of traffic volume in Busan area is found the largest and followed by Yeosu, Wando-Jeju area. Also, the traffic flow per area in 2000 has the same order.