• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.152-157
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• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.129-135
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• 2012

High speed casting technology is an attractive method to increase the productivity of continuous casting. However, high speed casting causes flow instability of molten steel in a mold. In this study, Large Eddy Simulation (LES) has been performed to identify the characteristics of mold flow for various shapes of submerged entry nozzles. The LES code has been newly developed to efficiently compute the two-phase flow by using the Fractional Step Method (FSM) combined with the Volume of Fluid (VOF) method. The Immersed Boundary Method was used to implement the shape of the submerged entry nozzle. Three cases of discharge angle of the submerged entry nozzle were computed and compared. The current results shed light on improving shape design of a submerged entry nozzle.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.4
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• pp.232-239
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• 2016

In this study, the two-way coupled analysis method of LES-WASS-2D and DEM has been newly developed to review numerically wave attenuation due to behavior of vegetation zone could not yet applied in numerical analysis. To verify the applicability, two-way coupled analysis method is analyzed comparing to the experimental result about characteristics of wave attenuation using vegetation. Numerically analyzed behavior and characteristics of wave attenuation according to height length, distribution length, spacing of vegetation zone and incident wave conditions. It was confirmed to be effective of 3~4% wave attenuation were increased height length and distribution length, narrowed spacing of vegetation. Finally, this study is applicable to behavior and wave attenuation prediction of vegetation zone.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.328-335
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• 2014

Numerical prediction methods were applied to investigate the turbulent air currents and air-conditioning efficiency in an underground subway station, and the results compared to experimental data. The Shin-gumho Station($8^{th}$ floor underground and 43.6m in depth) in Seoul was selected for the analysis. The entire station was covered for simulation and the ventilation mode was ordinary. The ventilation diffusers were modeled as 95 square shapes of $0.6m{\times}0.6m$ in the lobby and as 222 square shapes in the platform. Cooling air of $47,316m^3/h$ was supplied and the returned air of $33,980m^3/h$ is exhausted in the lobby and the cooling air of $33,968m^3/h$ is supplied and the returned air of $76,190m^3/h$ was exhausted in the platform which is the same as the experimental data. The cases of the screen-door-closed and open were respectively investigated. A total of 7.5million grids were generated and the whole domain divided into 22 blocks for MPI efficiency of calculation. Large eddy simulation (LES) was applied to solve the momentum and energy equation.

• Journal of Science of Art and Design
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• v.3
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• pp.33-61
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• 2001

Dans les arts modernes, nous ressentons souvent un $probl\`{e}me$ $disloqu\'{e}par$ rapport aux humains. Ceci ne viendrait-il pas $peut-\^{e}tre$ do notre $pens\'{e}e$ dans l' $\'{e}change$ culturelle entre le monde et nous qui s' appuie trop une $temporalit\'{e}$ et logique? Cette $the\`{s}e$ approche ce $probl\`{e}me$ $\`{a}$ travers one perception anthropologique do monde, en $\'{e}tudiant$ les arts tridimensionnels avec ses $\'{e}schelles$ qui deviennes plus on plus agrandis. Maurice Merleau-Ponty, dans son livre 'la $ph\'{e}nom\'{e}nologie$ de la perception', bien $r\'{e}sumait$ une $intersubjectivit\'{e}$ entre l' espace et nous. Selon lui, l' homme prend conscience do la forme des objets avec son environnement parce quil est un corps on interaction avec eux. Donc nous $r\'{e}f\'{e}rons$ ce livre pour notre set. Et on essayera ici d' $\'{e}tudier$ le travail do Constantin Brancusi, de Alberto Giacometti, do Richard Serra et do quelques d' autres travaux d' artistes L' oeuvre do Brancusi 'la Colonne sans fin', la taille plus de 29 m, produit one impression sur le spectateur relativement $\grave{a}$ la forme continue et $r\'{e}p\'{e}t\'{e}e$ $\`{a}$ linfini de $mani\'{e}re$ unifome. La pratique de Giacometti qui tenait compte do son envergure et de la longueur do son corps ainsi que do distance et de la mesure do sos bras, Il $d\'{e}formait$ aussi les silhouettes et transformait les objects en les $\'{e}tirant$ dans la perspective. Rosalind Krauss parler $\`{a}$ loeuvre do Serra, dans son livre 'l' originalit de lavant-garde et sutres mythes modernistes' (pp. 319-333), le spectateur est toujours on mouvement on liaison entre l' horizon do corps et celui do monde. Cette $transitivit\'{e}$ abstraite $r\'{e}ciproque$ entre le regardeur et le $regard\'{e}$, qui est comme le sujet de nombreuses oeuvres do Serra. Cependant le Maximalisme est $\`{a}$ l' origine Minimalisme qui s' $\'{e}tend$ dans ses efforts $th\'{e}oriques$ jusqu' au l' espace architecturale. Ces sculptures do grandes dimensions so situent autour de $b\^{a}timent$ ou dans lespace environnementale, comme ils sent l' architecture et le paysage. On suppose ici, leurs concepts de l' espace $\'{e}largit$ $\`{a}$ celui d' architecture. La sculpture et l' architecture $r\'{e}ciproque$ l' espace tridimensionnel entre eux, mais selon l' argument do Herbert Read pour la distinction de ces deux arts originaux sont, deux saisies de l' espace, ici englobant, $l\`{a}$ $englob\'{e}$. On $\'{e}tudie$ dans co set de concept de l' espace et de l' $\'{e}chelle$ d' objet par rapport au corps humain.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.1
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• pp.111-117
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• 2010

A three-dimensional numerical model is employed to investigate wave deformation due to a submerged structure. The three-dimensional numerical model solves the spatially averaged Navier-Stokes equations for two-phase flows. The LES(large-eddy-simulation) approach is adopted to model the turbulence effect by using the Smagorinsky SGS(sub-grid scale) closure model. The two-step projection method is employed in the numerical solutions, aided by the Bi-CGSTAB technique to solve the pressure Poisson equation for the filtered pressure field. The second-order accurate VOF(volume-of-fluid) method is used to track the distorted and broken free surface. A simple linear wave is generated on a constant depth and compared with analytical solutions. The model is then applied to study wave deformation due to a submerged structure and the predicted results are compared with available laboratory measurements.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.106-121
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• 2020

In order to make harbor outskirt facilities robust using the reliability-based design, probabilistic models of wave heights at varying stage of shoaling process optimized for Korean sea waves are prerequisite. In this rationale, we numerically simulate the nonlinear shoaling process of random waves over the beach with a sandbar at its foreshore. In doing so, comprehensive numerical models made of spatially filtered Navier-Stokes Eq., LES [Large Eddy Simulation], dynamic Smagorinsky turbulence closure were used. Considering the characteristics of swells observed at the east coast of Korean Peninsula, random waves were simulated using JONSWAP wave spectrum of various peak enhancement coefficients and random phase method. The coefficients of probabilistic models proposed in this study are estimated from the results of frequency analysis of wave crests and its associated trough detected by Wave by Wave Analysis of the time series of numerically simulated free surface displacements based on the threshold crossing method. Numerical results show that Modified Glukhovskiy wave height distribution, the most referred probabilistic models at finite water depth in the literature, over-predicts the occurring probability of relatively large and small wave heights, and under predicts the occurrence rate of waves of moderate heights. On the other hand, probabilistic models developed in this study show vary encouraging agreements. In addition, the discrepancy of the Modified Glukhovskiy distribution from the measured one are most visible over the surf zone, and as a result, the Modified Glukhovskiy distribution should be applied with caution for the reliability-based design of harbor outskirt facilities deployed near the surf-zone.

• Journal of computational fluids engineering
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• v.21 no.4
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• pp.1-10
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• 2016

The analysis of characteristics of turbulent flow and thermal boundary layer for natural convection caused by fire along vertical wall is performed. The 4m-high vertical copper plate is heated and kept at a uniform surface temperature of $60^{\circ}C$ and the surrounding fluid (air) is kept at $16.5^{\circ}C$. The flow and temperature is solved by large eddy simulation(LES) of FDS code(Ver.6), in which the viscous-sublayer flow is calculated by Werner-Wengle wall function. The whole analyzed domain is assumed as turbulent region to apply wall function even through the laminar flow is transient to the turbulent flow between $10^9$<$Gr_z$<$10^{10}$ in experiments. The various grids from $7{\times}7{\times}128$ to $18{\times}18{\times}128$ are applied to investigate the sensitivity of wall function to $x^+$ value in LES simulation. The mean velocity and temperature profiles in the turbulent boundary layer are compared with experimental data by Tsuji & Nagano and the results from other LES simulation in which the viscous-sublayer flow is directly solved with many grids. The relationship between heat transfer rate($Nu_z$) and $Gr_zPr$ is investigated and calculated heat transfer rates are compared with theoretical equation and experimental data.

• 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.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.1-9
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• 2014

To investigate the flame dynamics in an annular combustor with single swirl injector, a 3D large-eddy simulation (LES) and a level-set flamelet turbulent combustion model have been implemented. The LM6000 developed by GEAE has been used as the combustor of concern and boundary conditions are based on experimental data. The strong central toroidal recirculation zone induced by the volume expansion of the combustion gas and the vortex breakdown continuously occurred through the procession of the vortex with decreasing strength, are observed.