• Journal of Korean Society on Water Environment
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• v.27 no.1
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• pp.30-35
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• 2011

2D pollutant transport model was applied to the simulation of contaminant transport in the channel. At first, two kinds of virtual channels having different slopes were designed. The distribution of contaminant, which flows from one of the three drainages to the main channel, was simulated by each 2D model. Concentrations of 745 nodes were converted to input data of neural network model (Multi-perceptron) for training and verification using matrix. The first three cases (Case A-1, A-2, A-3) were used for training Multi-perceptron, the other three cases (Case B-1, B-2, B-3) were used for verification. As a result, Multi-perceptron reasonably divided the cases into the three characteristics which have different contaminant distributions due to the different input point of water pollution source. It can be a useful methodology for the water quality monitoring and backtracking.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.217-223
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• 2014

In order to suggest the methodology for improving the equity of flow distribution in open channel with multiple outlet, CFD simulations were carried out for actual scale distribution channel being operated in domestic G_WTP(Water Treatment Plant). Also, before and after installing the longitudinal multi hole(diameter=250 mm, 116 holes) baffle suggested by this research, turbidity measurements data were collected for evaluating the effects of hydraulic modification for inlet flow equity. From the both results, total turbidity of settled water was lowered by 30 % and equity of flow distribution was improved about 60 % compared with before hydraulic structure modification.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.135-142
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• 2009

In this investigation, we prepared a 1 and 3-parallel serpentine single PEMFC, which has an active area of $100\;cm^2$ and a flow channel cross section of $1{\times}1mm$. Distribution and transport of water in a non-operating PEMFC were observed by varying flow types and the flow rates (250, 400, and 850 cc/min). This investigation was performed at the neutron imaging facility at the CO1d Neutron RAdiography facility (CONRAD), HMI, Germany of which the collimation ratio and neutron fluence rate are 250, $1{\times}10^{6}n/s/cm^2$, respectively. The neutron image was continuously recorded by a scintillator and lens-CCD coupled detector system every 10 seconds. It has been observed that although the distilled water was supplied into the cathode channel only, the neutron image showed a water movement from the cathode to the anode channel. The water at the cathode channel was completely discharged as soon as the pressurized air was supplied. But the water at the anode channel was not easily removed by the pressurized air except for the 3-parallel serpentine type with 850cc/min of air flow rate. Moreover, the water at the MEA wasn't removed for any of the cases.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.208-216
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• 2019

This study investigated design factors and removal efficiencies of a sheet flow channel as natural type water improvement techniques in the stream. The channel was designed considering the design factors, then constructed and monitored in the test bed of the Osan stream's floodplain. Water lever, velocity, discharge, T-P, T-N, and NO₃-N were monitored and the removal efficiencies and design formula were suggested. Overall efficiencies of T-P, T-N, and NO₃-N range 10 - 20%, and they show consistent relations with residence times. Minimum velocity requirement is also suggested from the relation of algae conditions and velocities. Relation formula of residence time and removal efficiency will be applicable in the design and operation process of a sheet flow channel.

• Journal of Environmental Science International
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• v.22 no.3
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• pp.291-301
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• 2013

Sediment from the upstream channel has been deposited near the Nakdong River Estuary Barrage (NREB) due to the mild slope and decreased velocity. The annual mechanical dredging to ensure the flood capacity has been performed to remove the deposited sediment. However, the dredging method is not considered as an effective countermeasure due to high cost and long time to operate. Therefore, many methods for sedimentation reduction have been proposed for NREB. Especially, the channel contraction method to mitigate sedimentation problem by changing the channel geometry from 2 km to 3 km upstream of NREB has been recently suggested as an effective countermeasure. However, there is the possibility that the channel contraction method induces flood level increase compared to original condition. Therefore, it is necessary to investigate quantitatively the flood level changes in the upstream and downstream section due to the channel contraction method for NREB. In this study, water level changes by 10% channel contraction of whole width has been evaluated using the HEC-RAS model and simulated with and without channel contraction for various flood discharge. As a result, water level in the section where the channel was contracted was decreased by 0.02 m and flood level at the upstream of channel contracted was increased up to 0.015 m for the 500-year flood.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.1
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• pp.8-14
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• 1985

A circulation water channel with observational section of $4m{\times}2.4m{\times}1m(length{\times}breadth{\times}depth)$ and the maximum channel flow speed of 2 m/sec was designed for model tests of fishing gears. It consists of 6 sections evenly divided for easy connection. Two observational acryl windows of $1.2m{\times}1.5m$ and 2cm thick are provided. Steel deflection plates, equally spaced in 20-40cm, are fixed at corners of the channel to reduce the loss of water pressure head through the channel. The flow in the channel is controlled by D.C. motor control system with 50 H.P. driving propeller system. A series of model testing capabilities for fishing gear have been examined and the results are as follows. 1) The speed of water flow was in the range from zero to 2.3 m/sec. 2) The difference between the velocity of channel flow along the center line and that along both sides in the channel was less than 0.2 m/sec.

• Journal of Korea Water Resources Association
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• v.45 no.2
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• pp.127-136
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• 2012

River is able to change by various environmental factors. In order to conduct river restoration design, it is necessary to evaluate the stable channel through the analysis of past and present river channels. River evaluation requires various data, such as geometry, hydraulic and hydrology, but there is a lot of difficulty to understand topographical information of river change on time and space due to a lack of past data by domestic conditions. This study was analyzed abandoned channel formation, changes in the vertical-section and cross-section length of rivers, and micro-landform changes etc using an image analysis technique. Purpose of this research is to evaluates the stable channel through a river channel morphology change from past and present river channels image. Mangyoung river was conducted artificial river maintenance through straight channel consolidation form 1920 to 1930 year. In the result river maintenance, mangyoung river length was decreased by 15 km and abandoned channels of six points were made. Since then, weir was continuously increased to control bed slope and use water. Install of weir was to be the reason of changes on channel width, thalweg, vegetated bar, sand bar, water area. Present Mangyoung river show that water area was temporary increased in upper and middle reach because of weir installation. Total sand bar was only decreased in upper channel. The change of vegetated bar and sand bar was slight recently. In this result, Mangyoung river is inferred to reach stabilized channel although there is some difference to the lower reach.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.414-418
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• 2005

A finite element model is developed for the numerical simulation of bed elevation change in a curved channel. The SU/PG (Streamline-Upwind/Petrov-Galerkin) method is used to solve 2D shallow water equations and the BG (Bubnov-Galerkin) method is used for the Exner equation. For the time derivative terms, the Crank-Nicolson scheme is used. The developed model is a decoupled model in a sense that the bed elevation does not change simultaneously with the flow during the computational time step. The total load formula with is used for the sediment transport model. The slip conditions are described along the lateral boundaries. The effects of gravity force due to geometry change and the secondary flows in a curved channel are considered in the model. For the verification, the model is applied to two laboratory experiments. The first is $140^{\circ}$ bended channel data at Delft Hydraulics Laboratory and the second is $140^{\circ}$ bended channel data at Laboratory of Fluid Mechanics of the Delft University of Technology. The finite element grid is constructed with linear quadrilateral elements. It is found that the computed results are in good agreement with measured data, showing a point bar at the inner bank and a pool at the outer bank.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.5
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• pp.581-587
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• 2007

In order to suggest the methodology for improving the equality of flow distribution in a distribution channel, wet tests were carried out for pilot plant which was scaled down to 1/8 of full scale distribution channel being operated in domestic K_water treatment plant. The correlation between various hydraulic variables and their effects on the equality of flow distribution was evaluated through wet tests using pilot plant. From the results of wet tests, the longitudinal baffle with orifices was installed in the distribution channel, the equality of flow distribution was improved on the condition that the Froude number in pilot plant was similar with that in the full scale channel. Also, the opening ratio of the orifices on the longitudinal baffled did not have influence on the performance of the equality of flow distribution when the average flow velocity and Froud number were relatively low (Froude number ${\fallingdotseq} 0.01$). In the other hand, the performance of the equality of flow distribution was improved with increasing the opening ration of on the longitudinal baffle under conditions of relatively high average flow velocity and high Froud number(${\gtrsim}0.1$)

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.39-47
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• 2005

The structural analysis and water pressure tests are performed for liquid rocket thrust chamber regenerative cooling channel specimens at room temperature condition. Material properties of copper alloy to be used in the elastic-plastic structural analysis are obtained by uniaxial tension test at room temperature. The plate-type cooling channel specimens are manufactured and performed water pressure test to verify the analysis results. The results of elastic-plastic structural analysis and water pressure test show resonable agreements though with minor differences and it is revealed that structural stability of regenerative cooling channel is highly affected by the manufacturing tolerances due to very thin cross-sectional thickness of the cooling channel.