• 한국가시화정보학회:학술대회논문집
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• 2003.11a
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• pp.103-106
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• 2003

An experimental investigation was peformed to study the characteristics of ER(Electro-Rheological) fluid water flow in a horizontal rectangular tube with or without D.C volatage. To determine some characteristics of the ER flow, 2D PIV(Particle Image Velocimetry) technique is employed for velocity measurement. This research found the mean velocity distribution with 0 kV/mm, 1.0kV/mm and 1.5kV/mm for Re = 0, 0.62, 1.29 and 2.26. When the strength of the electric field increased, the claster of ERF are clearly strong along the test tube and the flow rate decreased.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.233-236
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• 2002

The high-pressurized spray nozzle is used f3r special washing and cutting with strong impact force. The performance of this nozzle, which focused on spray penetration and radial dispersion, was mainly investigated to maximize the momentum and minimize the flow loss. Hence, our experimental research was conducted by changing the aspect ratio ranging from 0 to 3 with nozzle outlet of 1.1. The spray trajectory far high-pressurized water was experimentally investigated using PDPA diagnostics, which was available at spray downstream region. As the spray at upstream near the nozzle exit did not show the improved disintegration. The results showed empirical correlation with regard to non-dimensional axial velocity distribution, spray penetration, and radial spreading rate with photographic visualization.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.17-22
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• 2004

An experimental investigation was conducted to study the characteristics of turbulent swirling flow in an axisymmetric annuli. The swirl angle measurements were performed using a flow visualization technique using smoke and dye liquid for Re=60,000-80,000. Using the two-dimensional Particle Image Velocimetry method, this study found the time-mean velocity distribution and turbulence intensity in water with swirl for Re=20,000, 30,000, and 40,000 along longitudinal sections. There were neutral points for equal axial velocity at y/(R-r)=0.7-0.75, and the highest axial velocity was recorded near y/(R-r)=0.9. Negative axial velocity was observed near the convex tube along X/(D-d)=3.0-18.0 for Re=20,000.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1626-1632
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• 2019

Monitoring of environmental radioactivity is essential for ensuring the radiological safety of residents who live near nuclear power plants. Ulsan, South Korea, is surrounded by 16 nuclear power plants, the highest density in the country. In addition, the city contains facilities for conducting radiological nondestructive testing and using radioisotopes for medical purposes. It makes the confirmation of radiological safety particularly necessary. In this study, sampling points were selected based on regional characteristics, and surface water samples were pretreated and analyzed for gross beta and gamma radiation levels. In addition, the distribution of the city's gamma dose rate was determined using a mobile monitoring system and distribution visualization program. The results showed that there is no effect on the gross beta and gamma nuclides of artificial radionuclides, and the gamma dose rate of the entire region did not exceed the environmental radiation level in South Korea overall, confirming the radiological safety of the city.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.1-13
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• 2004

A scanning stereo-PIV system was developed to measure the three-dimensional distribution of three-component velocity in a turbulent round jet. A laser light beam produced by a high repetition rate YLF pulse laser was expanded vertically by a cylindrical lens to form a laser light sheet. The light sheet is scanned in a direction normal to the sheet by a flat mirror mounted on an optical scanner, which is controlled by a programmable scanner controller. Two high-speed mega-pixel resolution C-MOS cameras captured the particle images illuminated by the light sheet, and stereoscopic PIV method was adopted to acquire the 3D-3C-velocity distribution of turbulent round jet in an octagonal tank filled with water. The jet Reynolds number was set at Re=1000 and the streamwise location of the measurement was fixed at approximately x = 40D. Time evolution of three-dimensional vortical structure, which is identified by vorticity, is visualized. It revealed that the existence of a group of hairpin-like vortex structures was quite evident around the rim of the shear layer of the jet. Turbulence statistics shows good agreement with the previous data, and divergence of a filtered (unfiltered) velocity vector field was $7\%\;(22\%)$ of root-me an-squared vorticity value.

• Analytical Science and Technology
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• v.31 no.3
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• pp.122-133
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• 2018

In this study, groundwater quality data measured for 11 years from 2006 to 2016 were analyzed statistically for 101 civil defense emergency water supply facilities (CDEWSF) in the Gwangju area. The contamination level was quantified into four grades by using excess drinking water quality standards, average concentration analysis, and tendency analysis results for each facility. On the basis of this approach, the groundwater contamination degree of each item was evaluated according to land use status, installation year, depth, and geological distribution. The contamination grade ratios, which were obtained by analyzing three contamination indicators (water quality exceeded frequency, average concentration analysis, and trend analysis) for 15 items on statistically significant of civil defense emergency water was relatively high, in the order of Turbidity (51.5 %) > Color (32.7 %) > Nitrate nitrogen (28.7 %) > Hardness (25.7 %). As a result of the contamination grade analysis, except for the items of Turbidity, Color, and Nitrate nitrogen, the contamination levels were distributed in various degrees from "clean (0)" to "seriously contaminated (3)." Regarding the contamination grade of 12 items, 25 % of the total were classified as "possibly contaminated (1)," and 75 % were rated "clean (0)." The four items (Turbidity, Color, Nitrate nitrogen, and Hardness) for which contamination indication rate were evaluated as "high" by the were visualized on a contamination map.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.773-778
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• 2006

Velocity profiles inside a partially filled pipline have been investigated experimentally. To measure the velocity fields, a particle image velocimetry (PIV), which is a recent quantitative visualization technique, is applied. The velocity profile inside a circular pipe is well known, but if the pipe is partially filled, the problem is entirely different in the sense that the velocity distribution is significantly affected by the slope of pipe and filled water level, and so on. In order to calculate exact flow rate in the open channel or partially filled pipeline, three-dimensional velocity distributions at a given cross-sectional area are measured and compared the flow rates with the previously known empirical formula of Manning equation. The results show that the velocity profiles at center plane is considerably different from each other when the slope and water level change. Thus, The three-dimensional velocity profile can be the most plausible estimate for the exact flow rate.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.799-802
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• 2008

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.53-58
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• 2006

Along with the development of costal engineering, various type of breakwaters have been built. The main purpose of breakwaters are to provide harbour protection against waves, to stabilize beaches against erosion due to large wave action, and to provide for temporary wave protection for installation on or under water surface. This paper an application example of PIV system for analyzing the flow of Floating Breakwater with double barriers. We introduce an analysis method to predict the characteristics of flow around the neighboring fields of Floating Breakwater with double barriers in order to develop a high performance model. Flow visualization has conducted in circulating water channel by a high speed camera and etc. Flowing phenomenon according to velocity distribution and flow separation around the breakwater with double barriers were obtained by 2-D PIV system.

• Spatial Information Research
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• v.22 no.4
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• pp.39-47
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• 2014

The Yeongsan river estuary has a serious water quality problem due to the water stagnation and it is imperative to predict the changes of water quality for mitigating water pollution. EFDC(Environmental Fluid Dynamics Code) model was mainly utilized to predict the changes of water quality for the estuary. The EFDC modeling normally accompanies the large volume of modeling output. For checking the spatial distribution of the modeling results, post-processing for converting of the output is prerequisite and mainly post-processing program is EFDC_Explorer. However, EFDC_Explorer only shows the spatial distribution of the time series and this doesn't support overlay function with other thematic maps. This means the impossible to the connection analysis with a various GIS data and high dimensional analysis. Therefore, this study aims to develop a post-processing system of a EFDC output to use them as GIS layers. For achieving this purpose, a editing module for main input files, and a module for converting binary format into an ASCII format, and a module for converting it into a layer format to use in a GIS based environment, and a module for visualizing the reconfigured model result efficiently were developed. Using the developed system, result file is possible to automatically convert the GIS based layer and it is possible to utilize for water quality management.