• Journal of Korean Society of Water and Wastewater
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• v.24 no.6
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• pp.713-722
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• 2010

This paper has assessed the flow patterns and settling efficiency in the sedimentation basin using the particle tracking method of the CFD code and has reached the following conclusions: In the original design where no baffle is installed in the sedimentation basin, a large recirculating area where the flow stagnates is created in the right side of the sedimentation basin, with most of the particles moving to the left side of the sedimentation basin following the flow. This biased flow structure in the sedimentation basin reduces the residence time of particles and thereby undermines settling efficiency. The biased flow toward the left side of the sedimentation basin is alleviated by installing a baffle in the sedimentation basin, promptly reducing the fast flow of over 0.7 m/s in the inlet of the sedimentation basin to the rate below 0.2 m/s. In this paper's simulation conditions, if a one-sided baffle is to be installed in the sedimentation basin, placing it 15 meters away from the basin's inlet leads to the best settling efficiency; it has also been analyzed that installing a two-sided baffle-rather than a one-sided one-is a better option in terms of settling efficiency. The highest settling efficiency of 96.2% is achieved when the underwater length of the two-sided baffle is set at 8 meters.

• Journal of Environmental Science International
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• v.5 no.1
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• pp.35-41
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• 1996

For studying of coagulation and sedimentation in estuarine clay, we obtained several flow curves with various concentrations of sea water by using Coutte type rotational rheometer. The initial shear stress on high concentration of sea water was observed big, but after this, its value is decreasing with increasing shear rate. The maximum pick of shear stress is decreasing with the decreasing of concentration of sea water The trend is same totally above for viscosity. The sedimentation times with the concentration of sea water vary in $\infty$ ~ 5 minutes. The zeta potential is changed dramatically between 114 and 118 concentration of sea water. That is consistent with the sedimentation graph. From these results, the phenomena of coagulation and sedimentation can be explained with viscoelastic terms on structual formation among particles by the changes of surface potential affected from contacting sea water to dispersed particles.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.1183-1189
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• 2009

The sedimentation rate of particles in a suspension is a function of particle size, initial slurry water content and salinity. Many researches conducted on the behavior of dredged soils have centered on such factors. However, there have been few attempts to assess another important influence factor of seasonal water temperature on designing the placement of dredged materials. In this paper, the effect of seasonal water temperature on sedimentation characteristics of dredged clay was investigated with consideration of three different water temperatures, that are $5^{\circ}C$, $15^{\circ}C$, $35^{\circ}C$, which represent critical water temperatures in winter, spring or fall, and summer, respectively. A series of experimental results reveal that the sedimentation rates for the water temperature of $15^{\circ}C$ and $35^{\circ}C$ are very similar each other, but that of $5^{\circ}C$ that represents a winter season leads to a considerably delayed sedimentation compared to the others. This may be attributable to the retardation of ion-leaching from clay particles at low water temperature.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1997.10a
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• pp.73-76
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• 1997

The purpose of this study is to find sedimentation patterns variation in Saemangeum coastal sea region. Water circulations are calculated diagnostically from the observed water temperature and salinity data and wind data and tidal residual current. Three dimensional movements of injected particles due In currents, turbulence and sinking velocity are tracked by the Euler-lagrange method. Calculated sedimentation patterns of riverine material are highly similar to the observed ones.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.68-69
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• 2006

When an alloy such as Ni-W is liquid phase sintered, heavy solid W particles sedimentate to the bottom of the container, provided that their volume fraction is less than a critical value. The sintering process evolves typically in two stages, diffusiondriven macrosegregation sedimentation followed by true sedimentation. During macrosegregation sedimentation, the overall solid volume fraction decreases concurrently with elimination of liquid concentration gradient. However, in the second stage of true sedimentation, the average solid volume fraction in the mushy zone increases with time. It is proposed that the true sedimentation results from particle rearrangement for higher packing efficiency.

• Analytical Science and Technology
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• v.24 no.6
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• pp.429-434
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• 2011

In this study, a wet-sampler was developed for collection in water and simultaneous fractionation of micron-sized particles (e.g., pigment, airborne, etc.). In this new device, three cylinders (partially filled with water) through which air was forced to pass for sample collection are connected in a series. Particles of different sizes are collected in different cylinders, allowing simultaneous fractionation. An uniqueness of this new device is that it does not use any membrane filter. Microparticles are collected directly in cylinders filled partially with water. Also the particles are simultaneously fractionated within this device while they are being collected. The new device was employed for collection of airborne particles. The collected airborne particles were fractionated by using sedimentation field-flow fractionation, SdFFF), and observed with an optical microscopy (OM) for size and shape analysis. Also AAS and ICP-AES were used for composition analysis of the airborne particles. It is expected that the new device is applicable to collection and analysis of size distribution of various types of microparticles.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.34-45
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• 2001

In the persent study, we conducted numerical experiments using a three-dimensional baroclinic equation model and a Lagrangian method for clarifying the hydrodynamics in Osaka Bay under the yearly mean discharge and visualizing the behaviour of particles of different settling velocity discharged from Yodo River and sedimentation pattern on the sea bottom. Particles are transported from the Yodo River to the south direction by the residual circulation of the bay head at the first stage, and after most of suspended solids particles are settled down at any layer and returned in the south-east coastal area through bottom layers by an estuarine circulation. The results show that estuarine circulation plays an important part of suspended solids transportation in the Osaka Bay.

• Journal of Wetlands Research
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• v.19 no.4
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• pp.451-458
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• 2017

In this study, the removal efficiency of the wetland in terms of particulate matter and dead water zone through the application of baffles in the sedimentation were simulated with the use of Computational Fluid Dynamics (CFD) to determine the design of a cost-effective constructed wetland. As a result, it was analyzed that the application of the baffle in the sedimentation tank affect the flow and sedimentation rate. Fine particles such as $2{\mu}m$ and $5{\mu}m$ showed high sedimentation rate when the baffles are installed horizontally. large particles such as $10{\mu}m$ and $20{\mu}m$ showed also high deposition rate when the baffles are installed vertically. In addition, the vertical baffles is considered to be more efficient than other baffle types in terms of maintenance since the particulate matter are concentrated in narrow areas. Therefore, it is considered that the selection of the most applicable type of baffle depends on the design purpose of the wetland to be constructed.

• Bulletin of the Korean Chemical Society
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• v.24 no.8
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• pp.1172-1176
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• 2003

This study aims to investigate the applicability of Sd/StFFF and to develop a method for size characterization of urban airborne particles, focusing primarily on particles larger than about 1 mm. It was found that the airborne concentration vary with time, although no particular seasonal trend was observed. When averaged over time, the airborne concentration was the lowest in the park areas with 99 ㎍/m³. The apartment, industrial, and central city area showed similar levels of the airborne concentrations with 166, 170, and 171 ㎍/m³, respectively. The housing area showed the highest airborne concentration with 201 μg/m³ among all tested areas. A power-programmed Sd/StFFF was used for size analysis of airborne particles with the initial field strength of 300 rpm, $t_a$ = 4, $t_i$ = -16, p = 8, and the flow rate of 7 mL/min. It was found that urban airborne samples were mostly populated by particles having diameters between about 5 to 20 ㎛, although all have broad size distributions ranging up to about 50 ㎛. Under the Sd/StFFF condition used in this study, no significant differences were found in size distributions among the airborne particles collected at different urban sites, and also among those collected at different times.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.143-148
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• 1999

The purpose of this study is to find sedimentation patterns variation before and after Saemangeum reclamation. Water circulations are calculated diagnostically from the observed water temperature and salinity data and wind data and tidal residual current. Three dimensional movements of injected particles due to currents, turbulence and sinking velocity are tracked by the Euler-lagrange methoed. Calculated sedimentation patterns of riverine material are highly similar to the observed ones.