• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.485-490
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• 2007

The purpose in having a control rod on a buoy system is to control the motion of it. The system may be composed entirely of a single circular cylinder and a long mooring anchor cable. A control rod has one function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of the effects of mutual interference. then determine the stability characteristics of the body. In this paper, the study of control-rod-attached buoy's 2-dimensional section was accomplished. model tests and numerical simulations had been carried out with different diameters of control rods. and varying the Reynolds number $Re=5,000{\sim}25,000$ based on the cylinder diameter(D=50mm) to predict the performance of the body and the 2 frame particle tracking method Iud been used to obtain the velocity distribution in the flow field. 50mm circular cylinder Iud been used during the whole experiments and measured results had been compared with each other.

• Nuclear Engineering and Technology
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• v.33 no.3
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• pp.315-326
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• 2001

Direct ECC bypass phenomena that occur in a reactor vessel downcomer with a Direct Vessel Injection (DVI) system during the reflood phase of a Large Break Loss-of-Coolant Accident (LBLOCA) are experimentally investigated using a transparent l/7.5 scaled down test facility of the Upper Plenum Test Facility (UPTF). A series of separate effect tests are peformed in order to investigate the mechanisms of direct ECC bypass and to find out its scaling parameters. Various flow regimes and phasic distribution in downcomer are identified and mapped, and the fraction of direct ECC bypass is measured under a wide range of air and water injection conditions. From the counterpart test of the UPTF Test 21-D, the dimensionless gas velocity ( $j^{*}$$_{g,eff}$) is derived experimentally, which is believed to be a major scaling parameter for the fraction of direct ECC bypass. And it is found out that the direct ECC bypass is greatly affected by the spreading width of ECC water film and the geometric configuration of the downcomer.r.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.247-257
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• 2021

The study area has been contaminated with explosive materials and heavy metals for several decades. For the design of the pump and treat remediation method, groundwater flow before and during groundwater pumping in a contaminated aquifer system was simulated, calibrated, and predicted using a generalized multidimensional hydrological numerical model. A three-dimensional geologic formation model representing the geology, hydrogeology, and topography of the aquifer system was established. A steady-state numerical simulation with model calibration was performed to obtain initial steady-state spatial distributions of groundwater flow and groundwater table in the aquifer system before groundwater pumping, and its results were illustrated and analyzed. A series of transient-state numerical simulations were then performed during groundwater pumping with the four different pumping rates at a potential location of the pumping well. Its results are illustrated and analyzed to provide primary reference data for the pump and treat remediation method. The results of both steady-state and transient-state numerical simulations show that the spatial distribution and properties of the geologic media and the topography have significant effects on the groundwater flow and thus depression zone.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.1
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• pp.78-90
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• 2005

The spatial and temporal distribution of soil moisture was characterized from soil moisture data through the intensive monitoring using Time Domain Reflectometry (TDR). The recession of soil moisture after a rainfall event was characterized and the empirical equation was used in the recession curve analysis. Recession analysis provides features of soil moisture variation such as recharge and stability depending upon locations of monitoring. The wetness index was useful for explaining spatial and temporal distributions of soil moisture and recession characteristics at hillslope scale.

• Proceedings of KOSOMES biannual meeting
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• 2007.05a
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• pp.169-174
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• 2007

The purpose in having a control rod an a buoy system is to control the motion of it. The system may be composed entirely af a single circular cylinder finder and a lang mooring anchor cable. A control rod has one function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of the effects of mutual interference, then determine the stability characteristics of the body. In this paper, the study of control-rod-attached buoy's 2-dimensional section was accomplished. model tests and numerical simulations had been carried out with different diameters of control rods. and varying the Reynolds number $Re=5,000{\sim}25,000$ based an the cylinder diameter(D=50mm) to. predict the performance af the body and the 2 frame particle tracking method had been used to obtain the velocity distribution in the flaw field 50mm circular cylinder had been used during the whale experiments and measured results had been compared with each other.

• Journal of ILASS-Korea
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• v.14 no.2
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• pp.59-64
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• 2009

These experiments are close examination of spray characteristics that are continuous liquid jet and modulated liquid jet. The experiments were conducted using water, over a range of crossflow velocities from $42{\sim}l36\;m/s$, with modulation frequencies of $35.7{\sim}166.2\;Hz$. Between continuous crossflow jet and modulated cross-flow jet of penetration, breakup point, spray angle and macro spray shape are experimentally investigated with image analysis. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than modulation effect. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of modulation frequency, SMD inclination of the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various modulation frequency was same distribution. And volume flux was decreased when the modulation frequency increase.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.1
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• pp.27-41
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• 2008

Distribution characteristics of phytoplankton community were investigated by HPLC and flow cytometry in Jeju Strait and the Northern East China Sea (NECS) in May 2004, in order to understand the relationship between physical environmental factors and distribution pattern of phytoplankton communities. Based on temperature and salinity data, three distinct water masses were identified; warm and saline Tsushima Warm Current (TWC), which is flowing from northwest of Jeju Island, warm and low saline water at the center of Jeju Strait, which is originated from China Coastal Water (CCW) and relatively cold and high saline water originated from Yellow Sea at the bottom of the Jeju Strait. At Jeju Strait, less saline water (<33 psu) of 15 km width occupied surface layer up to 20 m which located at 20 km offshore and strong thermal front between warm and saline water and cold and less saline water was found in the middle of the Jeju Strait. Vertical transect of temperature and salinity at the NECS also showed that low saline (<33 psu) water occupied the upper 20 m layer and cold and saline water was present at the eastern part. Chl a was measured as $0.06{\sim}3.07\;{\mu}g/L$. Spring bloom of phytoplankton was recognized by the high concentrations of Chl a at the low saline water masses influenced by the CCW and subsurface chlorophyll maximum layer appeared between $20{\sim}30\;m$ depth, which was at thermocline depth or below. Abundances of Synechococcus and picoeukaryote were $0.2{\sim}9.5{\times}10^4\;cells/mL$ and $0.43{\sim}4.3{\times}10^4\;cells/mL$, respectively. Dinoflagellate, diatom and prymnesiophyte were major groups and minor groups were chlorophyte+prasinophyte, chrysophyte, cryptophyte and cyanophyte. Especially high abundance of dinoflagellate was identified by high concentration (>1\;{\mu}g/L$) of peridinin at the bottom of the thermocline, which showed an outbreak of red tide by high density of dinoflagellates. Abundances of picoeukaryote in Jeju Strait were about $5{\sim}10$ times higher than abundance measured in Kuroshio water and showed a good correlation with Chl b (Pras+Viola), which implies the most of population of picoeukaryote was composed of prasinophytes. Prochlorococcus was not detected at all, which suggests that Kuroshio Current did not directly influenced on the study area. Based on the strong negative correlations between biomass of phytoplankton (Chl a) and temperature+salinity, the primary production and biomass of phytoplankton in the study area were controlled by the nutrients supply from CCW.

• Journal of Korea Water Resources Association
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• v.35 no.3
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• pp.261-274
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• 2002

The purpose of this study was to develop two dimensional contaminant transport numerical model by finite element method. The developed model system was tested for water quality analysis when contaminants from tributaries and sewage treatment Plants flow into the main river. In this study, the model was to perform calibration for reasonable parameter production and verification for reliability and accuracy. And, the proposed model was applied on the downstream of Han river using calibrated parameters. These results represented real con taminant distribution profile along the channel, and produced the good agreement in comparing calculated vague with measured value.

• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.1
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• pp.20-27
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• 2004

The hydro-dynamical and ecological coupled model were applied in the Tokyo Bay, to evaluate the flow pattern including water quality parameters and the distribution of biomass flux, and to compare with the results obtained from the satellite data during March 2001. The flow pattern and salinity distribution obtained from the present model were nearly identical with those of the previous studies. SST from NOAA/AVHRR was $2.5^{\circ}C$ higher than model results in the mouth of bay and $0.5^{\circ}C$ lower than model results in the inner bay, respectively. It was found that the concentration of chlorophyll-a estimated from SeaWiFS was considerably higher than that of model result, regardless similar distribution pattern. This disagreement will be studied through the more elaborate investigation in the future.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.399-403
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• 2004

생태 수리학적 측면에서 수질 개선에 기여하는 깔따구들이 흐름 구조에 따라서 어떻게 분포하는지를 파악하기 위해 수리 실험을 수행하였다. ADV로 유속을 측정하였으며, 자기 다른 유속 조건하에서 유기물질과 깔따구들을 투입하였다. 취득한 유속자료를 이용하여 흐름구조를 파악하였으며, 난류특성인 난류 전단응력을 분석하였다. 유기물질과 깔따구들은 상대적으로 유속이 느리고 전단응력이 작게 나타나는 지점에 분포하였다. 깔다구들이 굴을 파고 서식을 하였더라도 흐름에 의해 서식처가 옮겨짐을 확인 하였으며, 서식처 역할을 할 수 있는 반구 구조물 주위에 서식하였다. 유기물질의 퇴적 및 깔따구들의 서식은 주로 흐름 방향 유속 분포에 영향을 받으며, 이차류도 이것들의 분포에 중요한 역할을 하고 있다.