• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.49-55
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• 2003

When a body with slant angle after its shoulder is moving at high speed, the turbulent motion around the afterbody is generally associated with the flaw separation and determines the normal component of the drag. By changing the slant angle of afterbody, there exists a critical angle at which the drag coefficients change drastically. Understanding and control of the turbulent separated flows are of significant importance for the design of optimal configuration of the moving bodies. In the present paper, a new Large Eddy Simulation technique has been developed to investigate turbulent vortical motions around the afterbodies with slant angle. By basis of understanding the structure of turbulent flaw around the body, the new configuration of afterbodies are designed to reduce the drag of body and the nonlinear effects due to the interaction between the body configuration and the turbulent separated flows are investigated by use of the developed LES technique.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.4
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• pp.391-398
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• 2005

In this investigation, turbulent premixed combustion and flame front propagation in a gas turbine combustion chamber is studied. Direct numerical simulation of turbulent reacting flows demands extremely high computational resources, especially in more complicated geometry. The alternative choice may be left for Large Eddy Simulation (LES) by which only large scales are solved directly. In combustion problems, capturing the large scales' behavior without solving the details of small scales is a difficult task. Using a transport equation for description of the flame front propagation and therefore avoiding the calculation of inner flame structure is the basic idea of this study. For this purpose. the so-called G-equation has been used by which any iso-level of the G variable provides the flame location. A comparison with the experiment indicates that the present method can predict a turbulent velocity field and also capture a instantaneous 3-dimensional flame structure.

• Fire Science and Engineering
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• v.25 no.6
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• pp.58-63
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• 2011

This study is intended to present a computational thermal model for the combustibles in a residential building. As the Performance Based Design is more popular, fire-intensity and fire-load have turned out to be very important factors for building design and can be predicted through some computational work. To predict and estimate the thermal properties of the residential combustible fire, we made some numerical models of combustibles in a residential building. In a bid to validate the estimate values, computational analysis results from numerical models were compared with real fire tests. For computational analysis, the Fire Dynamics Simulator was used with Large Eddy Simulation model for turbulence. Consequently, each heat release rate and total heat release curves were successfully estimated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.5
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• pp.383-389
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• 2014

POD analysis has been done to investigate the internal flow characteristics using LES calculation results of hybrid rocket combustion chamber. The special emphasis was put on the change in the mode energy distribution caused by the installation of diaphragm compared to the baseline case. Also the comparison was made to investigate the effect of wall blowing on the changes in the mode energy between the regions near and far from the diaphragm. For baseline case, POD results clearly distinguish the primary mode containing most of flow energy from the rest of flow modes (2-9 mode) depicting small scale modes. Also, the increase in the energy of flow modes 2-5 is responsible for the formation of relatively large scale structures due to diaphragm. In addition, the comparison of mode energy distributions of flow fields with diaphragm shows similar patterns in both wall blowing and no blowing case. This implies that the local increase in regression rate just after the diaphragm is directly associated with the increase in energy distributions of 2-5 modes.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.66-72
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• 2008

In this study, transient 3D numerical simulations were performed to analyze the characteristics of fire driven flow for smoke ventilation system operating conditions in the deeply underground subway station. The smoke flow patterns were compared and discussed under smoke fan operating mode and off mode in the platform. Soongsil Univ. station(line number 7)was chosen for simulation which was the one of the deepest underground subway stations in the each lines of Seoul. The geometry for model is 365m in length include railway, 23.5m for width, 47m for depth. Therefore 10,000,000 structured grids were used for fire simulation. The parallel computational method for fast calculation was employed to compute the heat and mass transfer eqn's with 6 CPUs(Intel 3.0GHz Dual CPU, 12Cores) of the linux clustering machine. The fire driven flow was simulated with using FDS code in which LES method was applied. The Heat release rate was 10MW and The Ultrafast model was applied for the growing model of the fire source.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4B
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• pp.429-439
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• 2008

The purpose of this study is to examine the characteristics of run-up height over sandy beach due to the shape of submerged breakwater. For the discussion on it in detail, 3-Dimensional numerical model with Large Eddy Simulation, which is able to simulate directly interaction of Wave Structure Sandy beach (hereafter, LES-WASS-3D; Hur and Lee, 2007) has been used to simulate run-up height over sandy beach as well as wave field around submerged breakwaters. Using the results obtained from numerical simulation, the effects of the shape of submerged breakwaters (crown height, crown width, crown length and submerged breakwater's slope gradient) on run-up height over sandy beach have been discussed related to the wave height distribution and characteristics of up-layer flow around ones.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.463-472
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• 2009

The aim of this study is to examine the effect of beach curvature on wave fields in coastal area with Submerged Breakwaters using the 3D numerical model that is able to simulate directly interaction of WAve Structure Sandy beach (LES-WASS-3D). At first, the adopted model was validated through the comparison with an existing experimental data and showed fairly nice agreement. And then, the numerical simulations have been performed to investigate the effect of according to the variation of beach curvature. Based on the numerical results, the wave height, mean surface elevation, mean flow around submerged breakwaters and longshore distributions of run-up height have been discussed in relation to the variation of beach curvature.

• Geotechnical Engineering
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• v.1 no.1
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• pp.59-72
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• 1985

This paper deals with the numerical analysis by the (mite element method introducing Biot's theory of consolidation and the modified Cambridge model proposed by Roscoe school of Cambridge University as constitutive equation and using Christian-Boehner's technique. Especially, time interval and division of elements are investigated in vies of stability and economics. In order to check the validity of author's program, the program was tested with one-dimensional consolidation case followed by Terzaghi's exact solution and with the results of the Magnan's analysis for existing banking carried out for study at Cubzac-les-ports in France. The main conclusions obtained are summarized as follows: 1. In the case of one-dimensional consolidation, the more divided the elements are near the surface of the foundation, the higher the accuracy of the numerical analysis is. 2. For the time interval, it is stable to divide 20 times per 1-lg cycle. 3. At the element which has long drain distance, the Mandel-fryer effect appears due to time lag. 4. Lateral displacement at an initial loading stage predicted by author's program, in which the load was assumed as not concentrative. but rather in grid form, is well consistent with the value of observation. 5. The pore water pressure predicted by author's program has a better accordance with the value of observation compared with Magnan's results. 6. Optimum construction control by Matsuo-Kawamura's method is possible with the predicted lateral displacement and settlement by the program.

• Korean Journal of Psychosomatic Medicine
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• v.6 no.2
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• pp.147-154
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• 1998

Objective : This study was designed to find the characteristics of MMPI that could influence the outcome of cognitive behavioral therapy(CBT) for panic disorder. Methods : 34 patients who met DSM-IV criteria for panic disorder with or without agoraphobia had completed 11 weekly sessions of cognitive behavioral therapy. All the patients were assessed with MMPI before the initiation of treatment. Five self-report measures including Beck Depression Inventory(BDI), Spielberger State-Trait Anxiety Inventory(STAI), Agoraphobic Cognition Questionnarie(ACQ), Body Sensation Questionnaire(BSQ), and Daily Anxiety Selfrating (0 - 8 scales) were also assessed as a pre- and post-treatment assessment. After the completion of treatment, patients were classified by the High End-State(HES) functioning group and the Low End-State(LES) functioning group for the data analysis. Results : 1) The LES group showed significantly higher scores in Hypochondriasis Scale(HS), Depression Scale(D), Hysterical Scale(Hy), Obsessive Scale(Pt), Schizophrenia Scale(Sc) and Validity Scale(F) of MMPI than the HES group. However, these differences gave impressions that the LES group had more severe symptoms rather than that they could be the factors influencing the outcome of CBT. 2) Though, the severity of symptoms of the LES group in the 5 measures of pre-assessment was basically higher than that of the HES group. The fact that both group showed the similar improvement between pre- and post-assessment supported the above interpretation. Conclusion : In regarding the above results, MMPI was not a proper tool that could provide the factors influencing the outcome of CBT. In the future study, the authors need to use a different tool that can find the personality characteristics more directly.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.4
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• pp.343-351
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• 2016

Cryogenic spray characteristics of a nitrogen swirl injector operating in supercritical environment have been numerically investigated. By comparing the equation of states(EOS) used for supercritical condition, SRK EOS was applied to predict the nitrogen thermodynamic property under supercritical environment. A Chung's method was implemented for the calculation of viscosity and conductivity and Takahashi's correlation based on Fuller's Theorem was implemented for the calculation of diffusion coefficient. By injecting the nitrogen with 5 bar differential pressure into 50 bar chamber filled with nitrogen, numerical simulation has been conducted. The dynamic Smagorinsky sub-grid scale (SGS) model has been compared with the algebraic Smagorinsky SGS model using FFT frequency analysis. The instability at the liquid film and gas core inside injector and the propagation of pressure oscillation into the injector has been investigated. The spreading angle of swirl injector obtained by numerical calculation has been validated with experimental result.