• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.52-58
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• 2019

This study numerically analyzed the icing process in a U-shaped pipe exposed to the outside by considering the mushy zone of freezing water. Numerical results showed that the flow was pulled outward due to the U-shaped bend in the freezing section exposed to the outside, which resulted in the ice wave formation on the wall of the bended pipe behind. At the same time, the formation of a corrugated ice layer became apparent due to the venturi effect caused by the ice. The factors affecting the freezing were investigated, including the change of the pipe wall temperature, the water inflow velocity, and the pipe bend spacing. It was found that, as a whole, the thickness of the freezing layer increased as the pipe wall temperature decreased. It was also found that the freezing layer became relatively thin when the inflow rate of water was increased, and that the spacing of the pipe bends did not significantly impact the change in the freezing layer.

• Journal of Korean Society on Water Environment
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• v.20 no.5
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• pp.473-479
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• 2004

A sedimentation basin (SB) at the inlet of an irrigation reservoir which was constructed using an auxiliary dam was monitored to evaluate its pollutant removal efficiency. Water sampling at three points, i.e., inflow stream, upstream and downstream of the reservoir, were taken 5 times before and after the construction of the SB in 1999 and 2003, respectively. No significant water quality variations in inflow stream were observed during these periods. The COD, T-N, T-P and SS removal efficiencies were 38, 24, 35 and 49%, respectively. The results indicated that those removal efficiencies significantly increased during the rainy season and COD removal efficiency, especially, was higher than others studies. The scale of SB in this study was rational as aspects of pollutant removal efficiency and hydraulic detention time. And it is recommended that SB, at inlet of an reservoir, should be constructed as completely separated structure from reservoir water body and having SAR Index from 0.7% to 1.0%.

• Water for future
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• v.27 no.3
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• pp.83-83
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• 1994

The major objective of this study is to analyze the water balance of the Keumgang Estuary Reservoir in the Keum River basin. This basin is one of the catchment area which water utilization is very complicated. For the study of this area, this paper is to evaluate the monthly river-inflow of the Keumgang Estuary Resorvoir. Here, two approach methods are proposed which can take care of the natural and the low flow. The results are as follows. The natural flow at the Keumgang Estuary Reservoir during the wet season was decreased to 8.4% and increased from 0.4% to 17.6% during the dry season by the effects of Deachung Reservoir at the upper basin. The monthly fluctuation of the low flow during My-June varies to a great extent, when large amounts of irrigation water are required.

• Journal of Korea Water Resources Association
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• v.47 no.11
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• pp.1027-1037
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• 2014

Flow and bed changes due to tributary inflow variation at the confluence of the Namhan River and the Geumdang Stream were analyzed in this study using a two-dimensional numerical model. As a result of the numerical analysis, the velocity downstream of the confluence was greater than the velocity upstream of the confluence in the main channel regardless of the magnitude of tributary inflow. However, as tributary discharge increased, the channel erosion was accelerated and the dry area was produced at the tributary. Due to the bed erosion at the tributary, sediment transport was increased and the eroded sediments were deposited in the confluence area. The deposition in the confluence area changed the flow direction at the main channel to the left side and the localized flow eroded the channel bed at the left side. Therefore, it is expected that bank failure due to continuous bed degradation is possible in this area.

• Journal of Environmental Science International
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• v.14 no.4
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• pp.397-404
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• 2005

In order to study the temporal variations of nutrients and chlorophyll-a in the Bottol Bada, three field observations were carried out on 20, 23 and 26 July, 2004. The low N:P values exhibit nitrogen deficiency during the periods of observation. This result is not representative of typical summer environment in the southern coast of Korea. The possible mechanisms are as follows: 1) The freshwater inflow was not sufficient for the supply of nitrogen because the total precipitation was 11.9 mm in July, 2004. This amount is no more than $5\%$ in normal precipitation in July. 2) There was an inflow of oceanic water under the subsurface into the Bottol Bada. Even though the oceanic water comprises more nutrients, it produces the stratification between the surface and the subsurface water and seems to prevent the supply of nutrinets to the surface layer. 3) The high chlorophyll-a concentration of $1.2 {\cal}ug/L$ was shown near the narrow channel between Gae-do and Geumo-do. This seems to be resulted from the inflow of water from Gamak Bay.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.81-89
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• 2023

Recently, due to global warming and urbanization due to the influence of abnormal weather, weather changes are increasing worldwide. Various measures have been proposed to reduce flood damage as flood volume increases due to problems such as an increase in impermeable area due to urbanization and reckless development. In this study, flow characteristics and overflow volume were analyzed using FLOW-3D, a three-dimensional CFD model, in accordance with changes in the cross-flow weir inlet angle installed in the meandering river section, and a basic study was conducted to evaluate the overflow capacity and calculate the flow coefficient. As a result of the analysis, the smaller the inflow angle of the transverse overflow, the lower the water level and flow rate of the main water flow after passing the transverse overflow, and the higher the inflow angle, the higher the water level and the flow rate. In addition, it was confirmed that the direct downstream flow rate decreased compared to the upstream flow rate when the inflow angle of the transverse overflow was 40° or higher.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.87-98
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• 2009

The objective of this study is to evaluate the effect of increasing instream flow at Gapcheon stream of Daejeon city by considering two virtual reservoirs upstream, respectively; Geum-gok reservoir and Koe-gok reservoir upstream, respectively. The paralleled and cascaded reservoir operations were performed including the existing Jang-an and Bang-dong reservoirs. The results are summarized as follows. Firstly, from the Bang-dong and Geum-gok cascaded reservoir's water balance analysis, instream flow of $6.83Mm^3$ was able to be supplied to downstream, and water supply indexes of Geum-gok reservoir were analyzed to have the rate of water supply divided by watershed area of 403.4 mm, the rate of water supply divided by rainfall of 33.0 %, the rate of water supply divided by inflow of 96.4 %, the rate of water supply divided by storage capacity of 81.9 %, and the rate of inflow divided by storage capacity of 112.3 %. Secondly, from the Jang-an and Geum-gok paralleled reservoir's water balance analysis, flow durations at Gapcheon station were analyzed to have Q95 (the 95th high flow) of $4.806m^3/s$, Q185 (the 185th high flow) of $2.217m^3/s$, Q275 (the 275th high flow) of $1.140m^3/s$, and Q355 (the 355th high flow) of $0.887m^3/s$. Thirdly, inflow to Koe-gok reservoir was simulated including the Jang-an and Bang-dong paralleled reservoir's water balance analysis, instream flow of $49.60Mm^3$ was able to be supplied from Koe-gok reservoir to downstream, and water supply indexes of Koe-gok reservoir were analyzed to have the rate of water supply divided by watershed area of 246.5 mm, the rate of water supply divided by rainfall of 19.4 %, the rate of water supply divided by inflow of 40.8 %, the rate of water supply divided by storage capacity of 412.1 %, and the rate of inflow divided by storage capacity of 1,189.8 %. Fourthly, daily streamflows at Gapcheon stream were simulated including outflows from Koe-gok reservoir, flow durations at Gapcheon station were analyzed to have Q95 (the 95th high flow) of $4.501m^3/s$, Q185 (the 185th high flow) of $2.277m^3/s$, Q275 (the 275th high flow) of $1.743m^3/s$, and Q355 (the 355th high flow) of $1.564m^3/s$. The conclusion appeared that the effect of increasing instream flow at Gapcheon stream from Koe-gok reservoir was more higher than that from Geum-gok reservoir.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.456-459
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• 2001

A relationship between the water quantity and the inflow pollutant loads of BOD, TN, and TP in So-okcheon of the upper Keum river in 2000 was investigated in this study. Daily streamflow of So-okcheon needed to compute the pollutant loads was estimated by the DAWAST model, because there is no measurement of the discharge. From a relative function of the inflow pollutant loads using DAWAST, BOD can be estimated by the relation of $y=145.31x^{1.06},\;TN\;by\;y=598.11x^{0.90}\;and\;TP\;by\;y=39.60x^{0.89}$.

• International Journal of Fluid Machinery and Systems
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• v.5 no.2
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• pp.49-59
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• 2012

The present study is devoted to the influence of a superposed radial inflow in a rotor-stator cavity with a peripheral opening. The flow regime is turbulent, the two boundary layers being separated by a core region. An original theoretical solution is obtained for the core region, explaining the reason why a weak radial inflow has no major influence near the periphery of the cavity but strongly affects the flow behavior near the axis. The validity of the theory is tested with the help of a new set of experimental data including the radial and tangential mean velocity components, as well as three components of the Reynolds stress tensor measured by hot-wire anemometry. The theoretical results are also in good agreement with numerical results obtained with the Fluent code and experimental data from the literature.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.512-518
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• 1999

Recently rainfall and water evel are monitored via on -line system in real-time bases. We applied the on-line system to get the rainfall and waterlevel data for the development of the real-time flood forecasting model based on SCS method in hourly bases. Main parameters for the model calibration are concentration time of flood and soil moisture condition in the watershed. Other parameters of the model are based on SCS TR-%% and DAWAST model. Simplex method is used for promoting the accuracy of parameter estimation. The basic concept of the model is minimizing the error range between forcasted flood inflow and actual flood inflow, and accurately forecasting the flood discharge some hours in advance depending on the concentration time. The flood forecasting model developed was applied to the Yedang and Topjung reservoir.