• Journal of Korean Society on Water Environment
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• v.27 no.2
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• pp.147-158
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• 2011

This study analyzed the linkage characteristics between road runoff and the nearest streams in mountain regions using a discriminant analysis. The road-to-stream linkage is an important characteristic to evaluate whether the contaminant on road surface is transported directly into the nearby channel system. This study evaluated a total of 51 drainage outlets of mountain roads near the Soyanggang Dam. The linkage between road and stream, slope and width of road, and other information necessary for the discriminant analysis have been collected by in situ investigation and by analyzing the Digital Elevation Model. Finally, as independent variables in the discriminant analysis, the contributing road representing the road characteristics (similar to the runoff from the road drainage outlet) and the distance and slope of the connecting channel between road and nearest stream were selected. Among these three, the distance was found to have the highest discriminant power, the contributing road the lowest. Using the discriminant function derived, 40 out of 51 cases (78.4%) were correctly discriminated and the remaining 11 cases (21.6%) were wrongly discriminated. Reasons of wrongly discriminated cases were mainly due to change in drainage outlet direction, excessive runoff, change in road-to-stream path, etc. This result also indicates that the road-to-stream linkage can be introduced or prohibited by exactly the same way.

• Korean Journal of Ecology and Environment
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• v.53 no.4
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• pp.390-407
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• 2020

This study was carried out to evaluate the restoration effect in the restored Yangjae stream and to draw up an adaptive management plan based on the results. As the result of evaluation on the restoration effect, the restored Yangjae stream was evaluated with low naturalness in both terms of the morphology of the stream and the composition and spatial distribution of vegetation. The diverse functional groups were introduced in the vegetation restoration, but the flooding regime, which is significant in the spatial distribution of riparian vegetation, were not correctly reflected. Exotic species or species that were not ecologically suitable for the location were introduced on the embankment and thus a measure to improve those problems is required. As the ecological principle was not reflected in the restoration plan, the stream was constructed as the double terrace structure. Therefore, the width of the waterway was narrowed further, and the waterfront was not designed to accommodate changes from flooding disturbance, making the micro-topography of the stream simpler and the naturalness lower. The adaptive management plan was prepared to improve those problems, and a plan for creating an ecological network was recommended to enhance the restoration effect.

• Journal of Industrial Technology
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• v.27 no.B
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• pp.229-233
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• 2007

This research investigated the way of generating the flowing of water in case of artificial fluctuation of river width by the unidimensional numerical analysis in order to reconstruct vertical and expanse features of flowing, and the problem of existing numerical analysis in accordance with local enlargement and reduction of river through hydraulic model experiments with results of numerical analysis. The result revealed that when the local section change in the same river is exist, it showed 0.93m in the case of no change of local section in the hydraulic model experiments and numerical analysis, however, it presented 1.645m on the occasion of local section changes in the hydraulic model experiments and numerical analysis. In other words, there was a significant difference in the existing numerical analysis, when there was a local section change. As a result of the experimental section for the enlargement and reduction of local river width, due to the sensitive change for fluctuation of flood discharge, there was a significant difference between numerical analysis and hydraulic model experiments. In addition, the result of comparison between the enlargement and reduction of local river width confirmed that the result of numerical analysis with hydraulic model experiments showed larger generation of deviation in case of enlargement of section than in case of reduction of section.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.6
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• pp.11-20
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• 2007

In order to make the way to determine the instream flow more practically, we have investigated many case studies and reviewed reports and papers. To validate instream flow level suggested by the case studies, DAWAST and HEC-RAS model were applied to the Gap-stream watershed in Daejeon city. Flow-duration analysis was performed both with the stream flow data gauged in the Indong, Boksu, and Hoeduck stations, and with the stream flow data estimated by the DAWAST model and the specific discharge method. Instream flow was determined among the flow-duration analysis, DAWAST, HEC-RAS model and mass balance approach. It was satisfied with various factors such as target water quality, water depth for eco-system and resorts, water surface width, flow velocity for landscape in dry season. The study suggested that the mean low flow could be replaced into the instream flow for the preliminary study because the instream flow considering ecosystem, landscape, water-friendly environment and water quality was generally close to the mean low flow.

• Fire Science and Engineering
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• v.22 no.1
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• pp.93-98
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• 2008

Full-scale fire extinguishment tests were conducted to develop loaded stream fire extinguishing systems for protecting underground transmission cables. The dimension of test mock-up was 5.5m height${\times}3m$ width ${\times}6m$ length, and six 154kV OF cables were piled up. Gasoline was used to ignite cates. Linear heat detection cables were installed on top of 154 kV OF cable and discharge nozzles were installed on the top and sidewalls, respectively. As a result, both surface fires and deap-seated fires were extinguished successfully within the specified 3 minutes by discharging loaded stream agent.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1580-1584
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• 2010

In this paper, we made an analysis of the effective optical pulse stream generation. This is different from conventional approaches, which use fiber or waveguide delay line circuits. The optical pulse multiplication phenomenon occurs when the optical pulse's spectral width is greater than the transfer bandwidth of the coupler used. Therefore, the effective optical pulse stream generation can be controlled by using fiber couplers with different equivalent transfer bandwidths. The pulse separation spacing is controlled by number of cascaded coupler in optical loop mirror coupler scheme.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.59-68
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• 2006

Flow separation of recirculation zone by increasing of flow and change of its direction at confluence results in backwater due to conveyance reduction. The hydraulic characteristics of flow separation are analysed by experimental results of flow ratios of tributary and main streams and approaching angles. The boundary of flow separation by dimensionless length and width is defined by the streamline of zero and this definition agrees well to the existing investigation. Because flow separation doesn't appear in small flow ratio and approaching angle of $30^{\circ}$, the equation of flow separation with flow ratio and approaching angle is provided. In flow separation consideration and comparing with previous results, the existing equations of dimensionless length and width ratios by function of approaching angle, flow ratio, and downstream Froude number are modified and also contraction coefficient and shape factor are analysed. Dimensionless length and width ratios are proportional to the flow ratio and approaching angle. In analysis of water surface profiles, the backwater effects are proportional to the flow ratio and approaching angle and the magnitude at outside wall is greater than that of inside wall of main stream. The length, $X_l$ from the beginning of confluence to downstream of uniform flow, where the depth is equal to uniform depth, is characterized by width of stream, flow ratio, approaching angle, and contraction coefficient. The ratios between maximum water depth by backwater and minimum depth at separation are analysed.

• Wind and Structures
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• v.27 no.2
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• pp.101-109
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• 2018

Wall jet flow exists widely in engineering applications, including the simulation of thunderstorm downburst outflows, and has been investigated extensively by both experimental and numerical methods. Most previous studies focused on the scaling laws and self-similarity, while the effect of lip thickness and external stream height on mean velocity has not been examined in detail. The present work is a numerical study, using steady Reynolds-Averaged Navier Stokes (RANS) simulations at a Reynolds number of $3.5{\times}10^4$, of a turbulent plane wall jet with an external stream to investigate the influence of the wall jet domain on downstream development of the flow. The comparisons of flow characteristics simulated by the Reynolds stress turbulence model closure (Stress-omega, SWRSM) and experimental results indicate that this model may be considered reasonable for simulating the wall jet. The confined wall jet is further analyzed in a parametric study, with the results compared to the experimental data. The results indicate that the height and the width of the wind tunnel and the lip thickness of the jet nozzle have a great effect on the wall jet development. The top plate of the tunnel does not confine the development of the wall jet within 200b of the nozzle when the height of the tunnel is more than 40b (b is the height of jet nozzle). The features of the centerline flow in the mid plane of the 3D numerical model are close to those of the 2D simulated plane wall jet when the width of the tunnel is more than 20b.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.5
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• pp.1-17
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• 2013

We researched the fauna restoration of 5 urban streams in Ulsan established as ecological streams by improving water quality and river environment. The fauna inhabitation were compared according to the conditions of geometrical feature such as river width, low-water channel width, ect and water quality, water volumn, inland and forceland. The Mugeo cheon has clearly shown the fauna restoration effects resulting from supplying sustainable maintenance water and wastewater treatments. In the Yaksa cheon, on the other hand, the restoration effects were low due to the inflow of wastewater and sledges in some part of stream ever though the improvement of water quality. The Yeocheon cheon was found to have disadvantage on the ecological inhabitations due to supplying the maintenance water with highly concentrated salinity. The fauna restoration effect of the Meongjeong cheon was low due to the inflow of wastewater to the down stream. Therefore by supplying the maintenance water and improving the connection to the Taehwa river at the estuary, better restoration effects could be observed. In the Cheokgwa cheon, which is almost a natural river, the ecological integrity of the fauna population has been maintained quite well. It was concluded that the project to transform urban streams into ecological streams should focus on not only keeping water volume and quality but also maintaining favorable conditions for the migration and settlement of animal species close to the natural state.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.7
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• pp.849-861
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• 1997

In this study, the effect of hole geometry of the cooling system on the flow and temperature field was numerically calculated. The finite volume method was employed to discretize the governing equation based on the non-orthogonal coordinate with non-staggered variable arrangement. The standard k-.epsilon. turbulence model was used and also the predicted results were compared with the experimental data to validate numerical modeling. The predicted results showed good agreement in all cases. To analyze the effect of the discharge coefficient for slots of different length to width, the inlet chamfering and radiusing holes were considered. The discharge coefficient was increased with increment of the chamfering ratio, radiusing ratio and slot length to width and also the effect of radiusing showed better result than chamfering in all cases. In order to analyze the difference between the predicted results with plenum region and without plenum region, the velocity profiles of jet exit region for a various flow conditions were calculated. The normal velocity components of jet exit showed big difference for the low slot length to width and high blowing rate cases. To analyze the flow phenomena injected from a row of inclined holes in a real turbine blade, three dimensional flow and temperature distribution of the region including plenum, hole and cross stream with flow conditions were numerically calculated. The results have shown three-dimensional flow characteristics, such as the development of counter rotating vortices, jetting effect and low momentum region within the hole in addition to counter rotating vortex structure in the cross stream.