• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.237-239
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• 2003

The present study investigates on design optimization of rib-roughened two-dimensional channel to enhance turbulent heat transfer. Response surface method with Reynolds-averaged Navier-Stokes analysis is used as an optimization technique. Standard $k-{\varepsilon}$model with wall functions is adopted as a turbulence closure. The objective function is defined as a linear combination of heat transfer and friction drag coefficients with weighting factor. Computational results for overall heat transfer rate show good agreements with experimental data. Four design variables are optimized for weighting factor of 0.02.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.2
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• pp.229-237
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• 2003

The flow and heat transfer characteristics at the surface of two-dimensional protruding heated blocks using confined impingement multiple slot jets were computationally investigated Numerical predictions were made for round-edged nozzles at several nozzle-to-target plate spacings and jet-to-jet distances, with turbulent jet Reynolds numbers ranging from 2000 to 7800. The commercial finite-volume code FLUENT was used to solve the heat transfer characteristics and flow fields using a RNG $\textsc{k}-\varepsilon$ model. The computed heat transfer characteristics at the surface of heated blocks were in good qualitative agreement with previous experimental data The results of heat transfer characteristics on the surface of protruding heated blocks are important considerations in electronics Packaging design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.11
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• pp.1552-1558
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• 2002

The blade leading edge is modified to control the secondary flow generated in the turbine cascade with fence by intensifying the suction side branch of the horseshoe vortex. The incompressible Navier-Stokes equations are numerically solved with a high Reynolds number k-$\varepsilon$ turbulence closure model for investigating the vortical flows in the turbine cascade. The computational results of total pressure loss coefficients in the wake region are first compared with experiments for validation. The structure and strength of the passage vortex near the suction surface are examined by testing various geometrical parameters of the turbine blade leading edge.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.57-64
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• 2015

This paper describes a volume of fluid(VOF) method, mRHRIC for the simulation of free surface flows around ship hulls and provides its validation against benchmark test cases. The VOF method is developed on the basis of RHRIC method developed by Park et al. that uses high resolution differencing schemes to algebraically preserve both the sharpness of interface and the boundedness of volume fraction. A finite volume method is used to solve the governing equations, while the realizable ${\kappa}-{\varepsilon}$ model is used for turbulence closure. The present numerical results of the resistance performance tests for DTMB5415 and KCS hull forms show a good agreement with available experimental data and those of other free surface methods.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.475-480
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• 2001

The flowfield of transverse jet in a supersonic air stream subjected to shock wave turbulent boundary layer interactions is simulated numerically by Generalized Taylor Galerkin(GTG) finite element methods. Effects of turbulence are taken into account with a two-equation $(k-\varepsilon)$ model with a compressibility correction. Injection pressures and slot widths are varied in the present study. Pressure, separation extents, and penetration heights are compared with experimental data. Favorable comparisons with experimental measurements are demonstrated.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.652-657
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• 2001

Computational work using the axisymmetric, compressible, Navier-Stokes Equations is carried out to predict the discharge coefficient of mass flow through a micro-critical nozzle. Several kinds of turbulence models and wall functions are employed to validate the computational predictions. The computed results are compared with the previous experimented ones. The present computations predict the experimental discharge coefficients with a reasonable accuracy. It is found that the standard $k-\varepsilon$ turbulence model with the standard wall function gives a best prediction of the discharge coefficients. The displacement thickness of the nozzle wall boundary layer is evaluated at the nozzle throat and is well compared to a prediction obtained by an empirical equation. The resulting displacement thickness of the wall boundary layer is about 2% to 0.6% of the diameter of the nozzle throat for the Reynolds numbers of 2000 to 20000.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.6 no.3
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• pp.267-281
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• 1994

The Combustion gas behavior induced by fire in a building is numerically investigated. The typical building for this analysis is partially divided by a vertical baffle projecting from the ceiling. The solution procedure includes the low Reynolds number ${\kappa}-{\varepsilon}$ model for the turbulent flow and the discrete ordinates method is used for the calculation of radiative heat transfer equation. The effects of the location and size of fire source and baffle length on velocity and temperature distributions, species mass fraction and flame location are analyzed. As the results of this study, it is found that the case when the fire source is located at the vertical wall is more dangerous than at the bottom wall in view of the combustion products and flame location. It is also found that the radiation effect cannot be neglected in analyzing the building in fire.

• Fire Science and Engineering
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• v.6 no.1
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• pp.17-22
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• 1992

We have derived the general transfer equation for governing the continuity, energy transfer, mass and momentum transfer, and turbulent energy dissipation rate within the fire compartment which has the 800t fire source at the center of the floor. The governing transfer equations have been descretized using the finite volume approach and numerically experimented under the SIMPLE algorithm. In order for the SIMPLE algorithm approach to be physically reliable, the test results are compared with those of Morita's SOR Method using Conjugate Residual Method and found to be close to physical values though the computational convergence time still remains to be upgraded. The treatment of source terms in the system of finite difference equations has been critical in order to converge the governing equations within the appropriate time steps. The criteria of convergence allowance for the whole domain have been checked and the sudden change of the non-linear effects from the source term have been avoided. The criteria has been allowed to be for 5$\times$10$^{-5}$ .

• Journal of the Korean Society of Safety
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• v.10 no.1
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• pp.64-73
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• 1995

A preliminary study is performed in order to design an effective ventilation equipment for the control of possible pollutants in a workshop. To this end, the Patankar's SIMPLE methodology is used to investigate the flow characteristics of the contaminated thermal deflected jet which is encounted often in practical hood system. SIMPLE-Consistent algorithm is employed for the pressure-velocity coupling appeared in momentum equations. A two equation, k-$\varepsilon$ model is used for Reynolds stresses. The prediction data is compared well against the experimental results by Chang(1989). Considering the control of the wake due to its high turbulence together with the stagnant feature has been investigated in term of major parameters such as temperature and magnitude of the discharge velocity. Detailed discussions are made to reduce the size of the wake region which give rise to pollutant concentration stratification.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.526-529
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• 2008

Air Conditioner has become a popular comfort providing device since two decades, whether in an office or home especially for warm and wet climate countries. The RAC (Room Air Conditioner) is widely used in various working spaces and residences. It composed of heat exchager, cross-flow fan, stabilizer, rearguider and blade of diffuser region, etc. In this study, numerical analyses based on the prediction of transient phenomena were carried out to investigate the flow characteristics in the RAC, including the impeller, the rearguider, the stabilizer and the blade of the diffuser region. Using a commercial code, FLUENT, the velocity, pressure and streamlines were obtained with unsteady, turbulent flow and no-slip condition. The angular velocities of impeller are located in the 900 rpm. Turbulent closure was achieved using a standard k-${\varepsilon}$ model. A moving reference frame (MRF) approach was adopted to simulate the flow field generated by impeller in the RAC. Results were graphically depicted with various geometrical configurations and operating conditions.