• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.654-663
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• 2010

Attention has increasingly focused on the pollutant load discharged from rural area since the enforcement of total maximum daily loads (TMDLs) in korea. As one of the methods to control the inflow of pollutant load during wet weather events, local governments are attempting to apply non-point source control facility. To design those facilities appropriately, it is essential to understand the runoff characteristics of pollutants such as TSS, $BOD_5$, $COD_{Cr}$, TP and TN. In the paper, the quantitative analyses for pollutant runoff characteristics were examined in a small rural watershed with the area of about 53 hectares. For a dry weather day and wet weather events, variation patterns of dry weather flow and runoff characteristics of wet weather flows were monitored and investigated. The runoff model using XP-SWMM reflecting the landuse types of the watershed in detail was simulated to perform the sensitivity analyses for several factors influencing on their hydrograph and pollutographs. As a result, for the case of medium and small rainfall events (i. e. total rainfall of 35.8 and 17.5 mm), the impervious area including green house, roof and road which covers relatively low portion of total area (i. e. 16%) caused substantial first flush and the majority of total runoff load. Therefore, it has been concluded that the runoff characteristics of each pollutant and distribution of impervious area should be considered for the establishment of the control strategy of non-point pollutant runoff at a rural area.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.2
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• pp.62-73
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• 2001

The riparian environments of urban streams in Korea have been disturbed through the channelization for flood control and artificial land use as well as water pollution and flow decrease due to industrialization and urbanization. The flora and vegetation structure were investigated and an implication of stream restoration was discussed for the conservation of biodiversity in the riparian area of the Seunggi stream in Incheon. Naturalized plants and ruderal plants were widely distributed in the riparian area which was disturbed from cultivating, trampling, dumping etc. Submerged and floating hydrophytes were not found in the stream due to channelization and water pollution. Some halophytes were remained in downstream and reservoir after reclamation and embankment. The communities of Humulus japonicus, Panicum dichotomiflorum, Digitaria sanguinalis, Artemisia montana, Amaranthus retroflexus, and Aster pilosus were distributed in the disturbed area of bank slope and floodplain in the stream. As a natural potential vegetation, Phragmites australis in the wet meadow, Typha latifolia, Typha angustifolia, Oenanthe javanica, Persicaria thunbergii, and Penthorum chinense in the marsh, and Salix babylonica and Salix matsudana for. tortuosa in the woodland appeared in the floodplain. The topography in the stream played an important role on the distribution of riparian vegetation in the Seunggi stream. Appropriate methods for conservation and restoration of the riparian ecosystems must be planned on the basis of the actual vegetation in the disturbed urban stream.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.353-362
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• 2009

In the process of turbine modernizations, the investigation of the influences of water passage roughness on radial flow machine performance is crucial and validates the efficiency step up between reduced scale model and prototype. This study presents the specific losses per component of a Francis turbine, which are estimated by CFD simulation. Simulations are performed for different water passage surface roughness heights, which represents the equivalent sand grain roughness height. As a result, the boundary layer logarithmic velocity profile still exists for rough walls, but moves closer to the wall. Consequently, the wall friction depends not only on roughness height but also on its shape and distribution. The specific losses are determined by CFD numerical simulations for each component of the prototype, taking into account its own specific sand grain roughness height. The model efficiency step up between reduced scale model and prototype value is finally computed by the assessment of specific losses on prototype and by evaluating specific losses for a reduced scale model with smooth walls. Furthermore, surveys of rough walls of each component were performed during the geometry recovery on the prototype and comparisons are made with experimental data from the EPFL Laboratory for Hydraulic Machines reduced scale model measurements. This study underlines that if rough walls are considered, the CFD approach estimates well the local friction loss coefficient. It is clear that by considering sand grain roughness heights in CFD simulations, its forms a significant part of the global performance estimation. The availability of the efficiency field measurements provides an unique opportunity to assess the CFD method in view of a systematic approach for turbine modernization step up evaluation. Moreover, this paper states that CFD is a very promising tool for future evaluation of turbine performance transposition from the scale model to the prototype.

• Ecology and Resilient Infrastructure
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• v.1 no.1
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• pp.8-18
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• 2014

This study analyzes characteristics of flow using 3 dimensional numerical model, Delft3D, at the downstream of hydraulic structure. And fish shelters are suggested by analyzing them in flood time. A hydraulic structure changes flow conveyance, water depth and velocity affecting the activity of the fish. Flow depth decreases and velocity is fast near the left bank at the downstream of Gumi weir because of the concentration of flow due to it. Therefore, fish shelters are generated near the right bank of it. As a result of vertical velocity distribution which indicates the range of fish activity, maximum value are 0.0043 m/s in 30-year of return period of flood 0.0052 m/s in 50 year flood, 0.0046 m/s in 80-year of return period of flood, and 0.0039 m/s in 100-year of return period of flood. As the discharge increases, the areas of fish shelters decreases because depth and turbulent energy increase according to increases discharge. The estimated areas of fish shelters near the right bank decrease from 61.5% in 30-year of return period of flood to 39.0% 100-year of return period of flood. Therefore, the constructed hydraulic structures affect fish shelters.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.1
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• pp.1-8
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• 1995

Wastes produce groundwater contamination, offensive odor, and hazardous gases. This study investigates the contamination of groundwater at the Seokdae waste landfill area and seeks the desirable ways to minimize the groundwater contamination. Groundwater levels, water chemistry and aquifer characteristics of wells were examined around the Seokdae waste landfill. The water chemistry of the Dong stream, the groundwater distribution and flow were also studied. The results of this research show that the estimated quantity of the percolation from the landfill base to the ground is 520 ㎥/day and the extent of groundwater contamination is about 1-1.5 km from the center of the waste landfill. The groundwater contains heavy metals and other toxic elements. The conservation and management of the groundwater of the waste landfill need several monitoring wells to check the quantity and quality of groundwater, pumping wells to extract the contaminated groundwater, and slurry walls to protect the movement of contaminated groundwater.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.87-91
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• 1997

Ecological stability of the Lake Shihwa, artificially made by the construction of the Shihwa Dike, was evaluated by the species composition and variation in biomass of zooplankton. Species composition and seasonal variation in biomass in the seaside stations were similar to those observed in nearby bays and coastal zone. However, those in the lake sites showed very different patterns. The brackish water copepod, Sinocaianus tenellus, held the first rank in every season (with more than 66% in spring, 98% in summer and fall, and 80% in winter). The species composition was very simple and the biomass (in terms of total individuals $m^{-3}$) varied markedly with season up to the order of $10^4$ magnitude. These results imply that the lake ecosystem made by the construction of Sihwa dike is in very unstable stage probably due to the input of industrial wastes as well as unpredictable variation in salt content caused by irregular control of the watergate of the dike and resultant irregular flow direction of the water through the gate.

• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.738-745
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• 2015

The catalytic exchange of hydrogen isotopes between hydrogen and water has been known to be a very useful process for the separation of tritium from tritiated water. For the process, a highly active hydrophobic catalyst is needed. This study provides an effective fabrication method of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol) diacrylate] [Pt/poly(SDB-TPGDA)] hydrophobic catalyst beads with a narrow size distribution. Platinum nanoparticles were prepared by ${\gamma}$-ray-induced reduction in the aqueous phase first, and then uniformly dispersed in SDB-TPGDA comonomer after the hydrophobization of platinum nanoparticles with alkylamine stabilizers. The porous Pt/poly(SDB-TPGDA) hydrophobic catalyst beads were synthesized by the UV-initiated polymerization of the mixture droplets prepared in a capillary-based microfluidic system. The size of as-prepared catalyst beads can be controlled in the range of $200-1,000{\mu}m$ by adjusting the flow rate of dispersed and continuous phases, as well as the viscosity of the continuous phase. Sorbitan monooleate and cyclohexanol were used as coporogens to control the porosities of the catalyst beads.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.4
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• pp.296-301
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• 1993

A hydrodynamic solution for the lateral spreading of a river plume which was developed by assuming a Gaussian distribution of density difference between a turbulent jet river plume and ambient salt water is verified by the field data in the Nakdong river plume. Effect of the river plume on the transport of fine-grained suspended sediment at the Nakdong Estuary is also examined. The analysis of fold data showed a reasonably good correspondence with the theoretical solution adopted in this work Therefore, the hydrodynamic solution can be used as a useful tool in dealing with the lateral spreading of a river plume. The density stratification due to the existence of a river plume seems to cause a retarded settling of the suspended sediments in the water column. and thus a farther transport of the fine sediment is expected than in the normal steady flow.

• Analytical Science and Technology
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• v.26 no.4
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• pp.262-267
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• 2013

Gravitational field-flow fractionation (GrFFF) is a separation technique that utilizes earth's gravity as the external field. GrFFF is a convenient tool for the size and/or density-based separation of micron-sized particles of various origins. In this study, GrFFF was employed for size-based separation of oyster mushroom spores. Oyster mushroom spores have smooth surface and are of cylindrical to narrow kidney-shapes with 5 to 12 im in longer dimension and 3 to 4 im in shorter dimension, as was confirmed by optical microscope (OM). GrFFF conditions were optimized for separation and characterization of spores by varying the channel flow rate from 0.5 to 1 mL/min. During the GrFFF elution of the spores, 3 fractions were collected to confirm the growth of oyster mushroom spore. The collected fractions were incubated for 30 days in water to examine the influence of the size on the growth of the spores. Results suggested that the oyster mushroom spores collected at the middle part of the GrFFF fractogram grew faster than those collected at the beginning or at the end of the fractogram.

• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.565-574
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• 1998

The friction factor distribution of commercial pipes vary according to the pipe type and size. The present paper developed the friction factor equations of power law by analyzing the data reported by Colebrook(1938). Generally, pipe design requires pump power, discharge or pipe diameter for each condition given. Yoo(1995b) has suggested the basic equations for the explicit design of uniformly rough pipe and Yoo and Kang(1996) have refined those equations for the cases of uniformly rough pipe on a sloping bed with a pumping power. Furthermore Yoo and Kang(1997) have studied the design of commercial pipe for a general case. The approach gives relatively accurate solutions, but the equations obtained are rather complicated. In the present study two types of power law are developed for the friction factor of commercial pipe, and explicit forms of equations are generated by applying the power law friction factor equations for the simple design of commercial pipes.