• Wind and Structures
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• v.27 no.2
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• pp.89-100
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• 2018

3D simulations based on an impinging jet were carried out to investigate the flow field of a steady downburst and its effects on a high-rise building by applying the SST k-${\omega}$ turbulence model. The vertical profile of radial wind speed obtained from the simulation was compared with experimental data and empirical models in order to validate the accuracy of the present numerical method. Then wind profiles and the influence of jet velocity and jet height were investigated. Focusing on a high-rise building, the flow structures around the building, pressure distributions on the building surfaces and aerodynamic forces were analyzed in order to enhance the understanding of wind load characteristics on a high-rise building immersed in a downburst.

• Computers and Concrete
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• v.2 no.6
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• pp.455-479
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• 2005

This paper describes a 2D nonlinear finite element analysis (NLFEA) platform that combines heat flow analysis with realistic analysis of cracked reinforced concrete structures. The behavior models included in the structural analysis are mainly based on the Modified Compression Field Theory and the Distributed Stress Field Model. The heat flow analysis takes into account time-varying thermal loads and temperature-dependent material properties. The capability of 2D nonlinear transient thermal analysis is then implemented into a nonlinear finite element analysis program VecTor2(C) for 2D reinforced concrete membranes. Analyses of four numerical examples are performed using VecTor2, and results obtained indicate that the suggested nonlinear finite element analysis procedure is capable of modeling the complete response of a concrete structure to thermal and mechanical loads.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1493-1498
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• 2004

WSGGM with gray gas regrouping is successfully applied to study the flame structure of counter flow flames including effect of radiative transfer. The statistical narrow band model is used to obtain the benchmark solutions. Results obtained by using the optically thin model are shown to overestimate the emission and to predict the flame structures inadequately especially for optically thick and low stretch rate flames. Computed results by using the WSGGM with 10 gray gases and SNB model show reasonable agreements with each other, and the required calculation time for the WSGGM is acceptable for engineering applications.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.79-86
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• 1997

In this study, pre-postprocessing toolbox is developed to perform elasto-plastic analyze of underground structures with transient ground water flow. This toolbox is composed of three modules. The first is the data input processor for the structural analysis. The preprocessing Is using GUI (Graphic User Interface), which is consist of dialog box, pull down, and short-cut icon, etc. The second is the structural analysis module. The analysis is based on the elasto-plastic finite element method involving additional options such as ground excavation effect, transient ground water flow, and rock bolts behavior. The last is the postprocessing module. The postprocessing is able to verify the result of the structural analysis by the graphical simulation which visualizes the element mesh, the node displacements, the element stress states, the stress contour, the ground water surface, and the rock bolt stresses. Since various options are considered separately in this toolbox, it is easy to modify the module of each processing, and to update other functional modules for the given analysis conditions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.78-81
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• 2008

A numerical study of the unsteady flow in an over-expanded thrust optimized contour and compressed truncated perfect rocket nozzle is carried out in present paper. These rocket nozzles are subject to flow separation in transient phase at engine start-up and/or engine shut-down. The separation flow structures at different pressure ratios are observed. The start-up process exhibits two different shock structures such as FSS (Free Shock Separation) and RSS (Restricted Shock Separation). For a range of pressure ratios, hysteresis phenomenon occurs between these two separation patterns. A three-dimension compressible Navier-Stokes solver is used for the present study. One equation Spalart-Allmaras turbulence model is selected. The computed nozzle wall pressures show a good agreement with the experimental measurements. Present results have shown that present code can be used for the analysis of the transient flows in nozzle.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.31-44
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• 2019

This study simulated a control rod assembly (CRA), which is a part of reactor shutdown systems, in immersed and fluid flow conditions. The CRA was inserted into the reactor core within a predetermined time limit under normal and abnormal operating conditions, and the CRA (which consists of complex geometric shapes) drop behavior is numerically modeled for simulation. A full-scale prototype CRA drop test is established under room temperature and water-fluid conditions for verification and validation. This paper describes the details of the numerical modeling and analysis results of the several conditions. Results from the developed numerical simulation code are compared with the test results to verify the numerical model and developed computer code. The developed code is in very good agreement with the test results and this numerical analysis model and method may replace the experimental and CFD method to predict the drop behavior of CRA.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1099-1102
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• 2004

Liposomal restructuring induced by hemolytic Listeria monocytogenes was investigated by using flow cytometry. When added to calcein-entrapped liposomes, hemolytic, but not non-hemolytic, Listeria monocytogenes were able to induce reformation of vesicles. Such restructuring of liposomes was easily monitored by flow cytometry. Electron microscopy also indicated major changes in the challenged liposomal structures. The preliminary results described may offer a simple and fast method for monitoring liposomal restructuring and for differentiating between hemolytic and non-hemolytic bacteria.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.213-216
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• 2002

In this paper, flow patterns around two vertical cylinders were investigated numerically and experimentally Flow patterns between cylinders are very complex and interative. Changing gaps between cylinders the flow patterns are measured and numerically studied at a fixed comming velocity. The experiment has beeen conducted in circulating water channel with PIV system and manometer, and numerical analysis has been made by F.D.M. and multi block method. The results can be applied in the understanding and design of multiple pile array structures.

• The KSFM Journal of Fluid Machinery
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• v.11 no.6
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• pp.46-53
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• 2008

Flow structures in an axial compressor with a non-uniform tip clearance were predicted by solving a simple prediction method. For more reliable prediction at the off-design condition, off-design flow characteristics such as loss and flow blockage were incorporated in the model. The predicted results showed that flow field near the design condition is largely dependent on the local tip clearance effect. However overall flow field characteristics are totally reversed at off-design condition, especially at the high flow coefficient. The tip clearance effect decreases, while the local loss and flow blockage make a complicated effect on the compressor flow field. The resultant fluid induced Alford's force has a negative value near the design condition and it reverses its sign as the flow coefficient increases and shows a very steep increase as the flow coefficient increases.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.579-584
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• 2008

The importance and the interest of wind load have emphasized since the damage of the Jeju World cup Stadium and Main Stadium of Busan Asiad in 2002, and the appearance of high-rise buildings. In general, a evaluation for the wind load acting on structures have been carried out mainly through the wind tunnel test, but this technique has the huge shortcomings that consume too much cost and experimental time. However, with the rapid advances on computers, it is possible to analyze the wind pressure distribution acting on structures by numerical scheme. In this paper, to predict the wind pressure distribution acting on shell structures having the various shape by numerical simulation, governing equations of fluid flow and turbulent model is formulated. Also, evaluates the wind pressure coefficient in accordance with the structural shape for shell structures like as a membrane structures and dome structures.