• Journal of Korean Society of Water and Wastewater
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• v.24 no.4
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• pp.425-432
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• 2010

From the results of tracer test for the existing clearwell in Y water treatment plant, $T_{10}$ and T10/T were calculated as 150 min and 0.24, respectively. Therefore it required the modification schemes for improving hydraulic efficiency, surrogated by $T_{10}$ and $T_{10}$/T, and disinfection performance. In this study, using transient CFD(Computational Fluid Dynamics) simulation technique, tracer tests on dynamic condition for the suggested schemes were simulated. From the results of simulation, it was revealed that 8~6 baffles are necessary to guarantee the disinfection ability in the existing clearwell. Also, installing orifice baffle in the vicinity of inlet could increase plug flow fraction within clearwell.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.759-765
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• 2011

In this study, in order to investigate the effects of wall roughness on the hydraulic characteristics of chlorine contactor, CFD simulation and tracer tests were conducted for both of reactors whose walls are made of concrete and lined with PE(Poly Ethylene). In the case of walls contacted with water being lined with PE (relatively lower roughness), the flow within reactor is closer to plug flow than that in the case of concrete walls (relatively higher roughness). Especially, the longer tail of C-curve from the results of transient CFD simulation can tell that Morill index in the case concrete walls is much higher than that in the case of walls be lined with lower roughness material.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.519-525
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• 2010

From the results of tracer test for the existing chlorine contactor in Y water treatment plant, $T_{10}$ and $T_{10}$/T were calculated as 130 min and 0.16, respectively. Therefore it required the modification schemes for improving hydraulic efficiency, surrogated by T10 and $T_{10}$/T, and disinfection performance. In this study, in order to reduce dead zone within contactor, the installation of porous baffles in the near of each corner was suggested and verified using transient CFD(Computational Fluid Dynamics) simulation technique and tracer tests on dynamic condition. From the results of simulation and tracer tests, it was revealed that porous baffles installed have been effective to reduce dead zone within contactor, and increase plug flow fraction.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.1
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• pp.25-33
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• 2016

This paper describes three-dimensional computational fluid dynamics (CFD) simulation of liquid-liquid flow and transient tracer tests in a full-scale continuous stirred-tank reactor (CSTR) used for drinking water treatment. To evaluate the effects of inlet flow rate on hydrodynamic behavior in the selected CSTR, inlet flow rate was changed from 10% to 100% of the design flow rate. From the results of CFD simulation and analysis, as the inlet flow rate increases, Modal index and ${\beta}$ value are increased. Also, Morrill index shows local minimal points in relation to the inlet flow rate, which are observed at 20% and 40% of the design flow. As inlet flow Increases more than 40%, it is shown that Morrill index re-increases to close to ideal CSTR.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.582-590
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• 2007

In view of the analysis of the phenomena and the prediction of the performance, mathematical modelling and simulation of a high temperature pilot reactor for water gas shift reaction (WGSR) has been carried out. Multiscale simulation incorporated computational fluid dynamics (CFD) technique, which has the capability to deal with the reactor shape, fluid and energy transport with extensive degree of accuracy, and process modeling technique, which, in turn is responsible for reaction kinetics and mass transport. This research employed multiscale simulation and the results were compared with those from process simulation. From multiscale simulation, the maximum conversion of was predicted approximately 0.85 and the maximum temperature at the reactor was calculated 720 K, resulting from the heat of reaction. Dynamic simulation was also performed for the time transient profile of temperature, conversion, etc. Considering the results, it is concluded that multiscale simulation is a safe and accurate technique to predict reactor behaviors, and consequently will be available for the design of commercial size chemical reactors as well as other commercial unit operations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.971-977
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• 2015

A numerical analysis for the performance of compound gyroplane in forward flight was performed. TSM(Transient Simulation Method) was used to analyze the performance of autorotating rotor. CFD was conducted for the fuselages to recognize the variation of aerodynamic performance according to flight speed. At given conditions; airspeed, shaft angle and collective pitch, the quasi-static states of autorotation were determined and the variation of rotor performance was observed. Performance analysis results showed that the effect of aerodynamic characteristics in accordance with the shape of fuselage is so important that the streamlined fuselage is essential to fly fast. Forward flight speed limit is dependent on the autorotation performance of rotor.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.77-87
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• 2018

In the case of high-energy line breaks in nuclear power plants, supersonic steam jet is formed due to the rapid depressurization. The steam jet can cause impingement load on the adjacent structures, piping systems and components. In order to secure the design integrity of the nuclear power plant, it is necessary to evaluate the load characteristics of the steam jet generated by high-energy pipe rupture. In the design process of nuclear power plant, jet impingement load evaluation was usually performed based on ANSI/ANS 58.2. However, U.S. NRC recently pointed out that ANSI/ANS 58.2 oversimplifies the jet behavior and that some assumptions are non-conservative. In addition, it is recommended that dynamic analysis techniques should be applied to consider transient load characteristics. Therefore, it is necessary to establish an evaluation methodology that can analyze the dynamic load characteristics of steam jet ejected when high energy pipe breaks. This research group has developed and validated the CFD analysis methodology to evaluate the transient behavior of supersonic impinging jet in the previous study. In this study, numerical study on the transient load characteristics of supersonic steam jet impingement was carried out and amplitude and frequency analysis of transient jet load was performed.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.4
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• pp.92-102
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• 2012

The process of the wind noise analysis around an OSRVM is developed and is verified by simulating unsteady flow field past a generic OSRVM mounted on the flat plate at the Reynolds number of $Re_D=5.2{\times}10^5$ based on the mirror diameter. The transient flow field past a generic OSRVM is simulated with various turbulence models, namely DES-SA, LES Constant SGS, and LES Dynamic SGS. The sound radiation is predicted using the Ffowcs- Williams and Hawkings analogy. For the present simulation, the 6.35million cells are generated. Time averaged pressure coefficients at 34 locations on the surface of the generic OSRVM are compared with the available experimental data. Also, 12 Sound Pressure Levels located on the surrounding mirror are compared with the available experimental data. Both of them show good agreements with experimental data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.2
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• pp.137-143
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• 2008

In the present study, a forest fire spread was simulated with a three-dimensional, fully-transient, physics-based, computer simulation program. Physics-based fire simulation is based on the governing equations of fluid dynamics, combustion and heat transfer. The focus of the present study is to perform parametric study to simulate fire spread through flat and inclined wildland with vegetative fuels like trees or grass. The fire simulation was performed in the range of the wind speeds and degrees of inclination. From the results, the effect of the various parameters of the forest fire on the fire spread behavior was analyzed for the future use of the simulation in the prediction of fire behavior in the complex terrain.

• Journal of Korea Multimedia Society
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• v.15 no.3
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• pp.380-387
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• 2012

The present investigation is to examine the thermal behaviors of air flows inside Korean traditional house made of the construction materials transmitted. The methodology is numerical predictions of air flows depend on the temperature distribution inside the indoor spaces. The transient computational simulations are performed along with the different house types, weather condition, and operating time. Thermal properties of building units have been obtained by the parallel measurements and utilized in the numerical works. Consequently, the details of flows and temperature of air in the houses illustrate the thermal design of the traditional Korean house satisfy the requirements of human living.