• Journal of Environmental Impact Assessment
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• v.20 no.3
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• pp.337-348
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• 2011

Urban environmental problem became one of major issues during its urbanization processes. Environmental impacts are assessed during recent urban planning and development. Though the environmental impact assessment considers meteorological impact as a minor component, changes in wind environment during development can largely affect the distribution pattern of air temperature, humidity, and pollutants. Impact assessment of local wind is, therefore, a major element for impact assessment prior to any other meteorological impact assessment. Computational Fluid Dynamics (CFD) models are utilized in various fields such as in wind field assessment during a construction of a new building and in post analysis of a fire event over a mountain. CFD models require specially formatted input data and produce specific output files, which can be analyzed using special programs. CFD's huge requirement in computing power is another hurdle in practical use. In this study, a CFD model and related software processors were automated and integrated as a microscale wind environmental impact assessment system. A supercomputer system was used to reduce the running hours of the model. Input data processor ingests development plans in CAD or GIS formatted files and produces input data files for the CFD model. Output data processor produces various analytical graphs upon user requests. The system was used in assessing the impacts of a new building near an observatory on wind fields and showed the changes by the construction visually and quantitatively. The microscale wind assessment system will evolve, of course, incorporating new improvement of the models and processors. Nevertheless the framework suggested here can be utilized as a basic system for the assessment.

• Journal of ILASS-Korea
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• v.15 no.3
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• pp.140-149
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• 2010

The spray-wall impingement in diesel engines is important to mixture preparation, engine performance and pollutant emissions. The purpose of this paper is to study the effects of spray-wall impingement on fuel distribution, combustion and emission characteristics by using both experimental and numerical methods. To investigate the spray-wall impingement process, an impingement-chamber was designed and a visualization experiment system was also developed. The images of impinged spray and free spray were digitally recorded with an intensified CCD camera. To investigate the fuel distribution, combustion and emission characteristics of impinged spray in a real diesel engine, the fuel injection and combustion processes of an engine with impingement-chamber were simulated by CFD software. Equivalence ratio distribution results were obtained to understand the fuel distribution characteristics of the impinged spray. Some combustion and emission characteristics were also acquired and the results showed that ignition delay of impinged spray was shorter than that of free spray; NO emission of the impinged spray was significantly less than that of free spray, but soot emission of impinged spray was more than that of the free spray. This study found that the diesel engine with spray-wall impingement has significant potential to reduce NO emission.

• Applied Science and Convergence Technology
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• v.24 no.2
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• pp.27-32
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• 2015

We analyzed the destruction patterns of a turbo-molecular pump (TMP) resulting from its sudden exposure of a foreline to the atmospheric pressure due to a destruction of the foreline connecting clamp of an ICP dry etcher for 300 mm wafers during high-vacuum operation ($5{\times}10^{-6}$ Torr). Unlike in the case of view port's breakage, the TMP's rotor module was crashed inside the chamber. The primary damage resulted from the collision of the blades and stators, and the secondary damage resulted from the breaking of the rotor - driving shaft assembly. The fixing screws of the rotor and axial shaft were bent and broken when the TMP controller output the maximum current even after the crash event. Electrical power consumption analysis of the TMP power controller confirmed it. The stress distributions were analyzed by a finite element method using CFD-ACE+ multi physics software. Rotating inertia of each parts and kinetic energies were calculated as well. 68% of the rotational kinetic energy is deposited by the rotor - shaft module.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.1
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• pp.57-70
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• 2012

This article presents a numerical investigation concerning the effect of two kinds of axially progressing internal flows (namely, upward and downward) on fluid.structure interaction (FSI) dynamics about a marine riser model which is subject to external shear current. The CAE technology behind the current research is a proposed FSI solution, which combines structural analysis software with CFD technology together. Efficiency validation for the CFD software was carried out first. It has been proved that the result from numerical simulations agrees well with the observation from relating model test cases in which the fluidity of internal flow is ignorable. After verifying the numerical code accuracy, simulations are conducted to study the vibration response that attributes to the internal progressive flow. It is found that the existence of internal flow does play an important role in determining the vibration mode (/dominant frequency) and the magnitude of instantaneous vibration amplitude. Since asymmetric curvature along the riser span emerges in the case of external shear current, the centrifugal and Coriolis accelerations owing to up- and downward internal progressive flows play different roles in determining the fluid.structure interaction response. The discrepancy between them becomes distinct, when the velocity ratio of internal flow against external shear current is relatively high.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.641-648
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• 2016

In this study, the effect of injection nozzle shape on the supersonic film cooling performance is analyzed using CFD. The design parameters are inside and outside angles of upper plate of nozzle and nozzle tip thickness. It is observed that the mass flow rate of film cooling decreases with increase of inside angle, while the effect of the change of mass flow rate on the film cooling effectiveness is relatively small. In addition, cooling performance is generally reduced, except ahead of the local region where shock wave interaction with film cooling occurs, in accordance with the growth of the outside angle and tip thickness. In this paper, the CFD simulation is performed using a commercial software, ANSYS Fluent V15.0, and the CFD model is validated by comparing it with the experimental data shown in preceding research.

• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.353-362
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• 2000

Minimization of hemolysis is one of the key factors for successful axial flow blood pumps. It is, however, difficult to estimate the hemolytic performance of axial flow blood pumps without experiments. Instead, the Computational Fluid Dynamics(CFD) analysis enables the prediction of hemolysis. Three-dimensional fluid dynamics of axial flow pumps with different impellers were analyzed using the CFD software, FLOTRAN. The turbulence model k-$\varepsilon$ was used. The changes in turbulent kinetic energy applied to each particle (red blood cell) flowing through the pumps were computed and displayed by the particle trace method (particle spacing of 10 msec). Also, the Reynolds shear stress was calculated from the turbulent kinetic energy. The shear stress was higher behind the impellers than elsewhere. The CFD analysis could predict in vitro results of hemolysis and also the areas where hemolysis occurred. The CFD analysis was found to be a useful tool for designing less hemolytic rotary blood pumps.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.56-61
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• 2004

As the size and dimension of target problems in the field of computational engineering including CFD gets bigger and higher, it is needed to have more efficient and flexible data visualization environment in terms of software and hardware. Even though it is still manageable to use a mouse in controlling 3-dimensional data visualization, it would be beneficial to use 3-D input device for 3-D visualization. 'Data Glove' is one of the best 3-D input devices, because human hands are best tools understanding 3-D space. Signals coming from 'Data Glove' are analog and very sensitive to finger motions, so we decided to use a digital filter. This paper describes our experience and benefits of using data glove in controlling 3-Dimensional Postprocess Software.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.207-207
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• 2006

Hardware technologies for high-performance computing has been developing continuously. However, actual performance of software cannot keep up with the speed of development in hardware technologies, because hardware architectures become more and more complicated and hardware scales become larger. So, software technique to utilize high-performance computing systems more efficiently plays more important role in realizing high-performance computing for computational science. In this paper, the effort to enhance software performance on large and complex high-performance computing systems such as performance optimization and parallelization will be presented. Our effort to serve high-performance computational kernels such as high-performance sparse solvers and the achievements through this effort also will be introduced.

• Journal of Navigation and Port Research
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• v.32 no.1
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• pp.9-14
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• 2008

VOF method is known as one of the most effective numerical techniques handling two-fluid domains of different density simultaneously. Present study deals with the numerical analysis of flow field around bodies steadily moving near free-surface using FLUENT-VOF method. Validations were made by applying to three typical examples ; 2-D submerged hydrofoil, 3-D surface piercing body and container ship. It was found that the commercial software, FLUENT, is useful in practical use, and VOF method is capable of handling free-surface around moving bodies although discussions are limited to the analysis in qualitative sense.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.366-373
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• 2014

A conceptual design of a three-surface strike fighter was studied and stealth performance was taken into account to enhance survivability and battle effectiveness. CATIA was used to design the aircraft's three-dimensional prototype model and the weapon carriage arrangement was also studied. The aircraft's RCS characteristics and distributions under X, S, C, and L bands were simulated using the RCSPlus software, which is based on the PO method. Pressure and velocity distributions of the flow field were also simulated using CFD. A turbulence model was based on standard $k-{\varepsilon}$ function and N-S functions were used during the CFD computation. Lift coefficients, drag coefficients, and lift-to-drag ratio were obtained by aerodynamic simulation. The results showed that: (1) the average value of head-on RCS between ${\pm}30^{\circ}$ is below -3.197 dBsm, and (2) the lift coefficient is 0.34674, the drag coefficient is 0.04275, and the lift-to-drag ratio is 8.11087 when the attack angle is $2.5^{\circ}$.