• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.2
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• pp.287-298
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• 1989

A numerical work was performed to study the flow behaviors of the open channel type flow with its geometric boundary conditions being similar to that of the Multi-Stage-Flash evaporator with and without a baffle. For the analysis, two-dimensional steady turbulent flow was assumed and the widely known k-.epsilon. turbulence model was usded. SIMPLE algorithm and the power difference scheme were used for the numerical approach. Numerical results generally agree with the previous experimental results though there are some uncertainties at far downstream and near the free surface due to the three dimensionality of the flow and surface waves. Without a baffle, the flow has basically the shape of the submerged plane wall jet with its upper boundary at downstream being sharply curved toward the free surface. For the flow with a baffle, recirculation flow patterns are observed at the upper inlet portion and at the backside of the baffle. For the case without a baffle, it was also confirmed that the ratio between the liquid level and the gate opening height is the most important parameter to determine the flow behavior.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.1
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• pp.112-121
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• 1992

A numerical analysis was carried out to study two-dimensional turbulent natural convection in a square enclosure containing fluid of Prandtl number 6.05 within internal energy sources. The square enclosure was bounded by four rigid planes of constant equal temperature. Inclination angles of 0, 15, 30 and 45 deg. from the horizon for Rayleigh numbers from 1 * 10$^{6}$ to 1 * 10$^{9}$ were studied. Local and average Nusselts numbers are obtained on all four walls. If inclination angle exists, the average Nusselt number appears in increasing order at bottom, left, right and top wall.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.375-385
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• 1996

Turbulent flow and heat transfer characteristics around staggered tube banks were studied using the 3-D Navier-Stokes equations and energy equation governing a steady incompressible flow, which were reformulated in a non-orthogonal coordinate system with cartesian velocity components and discretized by the finite volume method with a non-staggered variable arrangement. The predicted turbulent kinetic energy using RNG $k-{\varepsilon}$ model was lower than that of standard $k-{\varepsilon}$ model but showed same result for mean flow field quantities. The prediction of the skin friction coefficient using RNG $k-{\varepsilon}$ model showed better trend with experimental data than standard $k-{\varepsilon}$ model result. The inclined flow showed higher velocity and skin friction coefficient than transverse flow because of extra strain rate ($\frac{{\partial}w}{{\partial}y}$). Also, this was why the inclined flow showed higher local heat transfer coefficient than the transverse flow.

• Journal of computational fluids engineering
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• v.20 no.1
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• pp.47-56
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• 2015

In this paper, we study the effect of various turbulence models by comparing the aerodynamic characteristics and the flow patterns computed for aircraft models. An in-house CFD solver, MSAPv, that solves the three dimensional RANS equations with the turbulence model equations is used. The turbulence models used in this study are the Spalart-Allmaras model, Menter's $k-{\omega}$ SST model, Coakley's $q-{\omega}$ model, and Huang and Coakley's $k-{\varepsilon}$ model. DLR-F6 WB and WBNP configurations are selected for the study. We concentrate on the separated flow pattern variations with the turbulence models at the wing-body junction and the wing-pylon junction as well as drag polar curves.

• Fire Science and Engineering
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• v.22 no.5
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• pp.1-8
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• 2008

The study is to perform numerical analysis of train fire characteristics in an underground subway tunnel, depending the different locations of ventilation facility. To study the characteristics of train fire, two kinds of worst-case scenarios are selected, based on escape distance, escape time, and fire zone, and trends and thermal environments of tunnel are analyzed by changing the locations of ventilation facility for times. Fire characteristics is calculated by using FLUENT v.6.3.26, and turbulent flow is calculated by using the standard k-${\varepsilon}$ model. The numerical results show distribution of carbon monoxide concentration, temperature, and velocity. The results of this study will contribute to building the most suitable ventilation systems when designing subway stations and tunnels.

• Fire Science and Engineering
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• v.17 no.3
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• pp.50-54
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• 2003

The backlayer phenomena of smoke in the road tunnel is evaluated through numerical experiments. A commercial code, PHOENICS is used to simulate smoke flow in the road tunnel. The independent and dependent variables are ventilation air velocity and the length of backlayer of smoke respectively. Hybrid scheme and $textsc{k}-\varepsilon$ turbulence model is adopted in the simulation process and mass residual is used as a convergence criterion. The experimental results say that the length of backlayer is reduced linearly with the increase of ventilating air velocity and that there is a critical air velocity which prevents from the onset of backlayering phenomena. One finds that there is a fresh air region near the bottom of tunnel which could make the passenger escape from the region polluted by smoke. These phenomena come from the severe vertical stratification of the smoke air mixture in the tunnel.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.10-16
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• 2003

The unsteady supersonic flow over tandem cavities has been analyzed by the integration of Navier-Stokes equations with the k-$\varepsilon$ turbulence model. The unsteady flow is characterized by the periodicity due to the mutual relation between the shear layer and the internal flow in cavities. The upwind TVD scheme based on the flux vector split with the van Leer limiters is used. The results show the principal frequency is very reasonable. The principal frequency of the rear cavity due to the front cavity has been analyzed by the combination of the several aspect ratios of cavities. In the case of the front cavity of low aspect ratio, the frequencies of tandem cavities are almost same, because two shear layers developed from each cavity are mixed and developed to one shear layer. However, in the case of the front cavity of high aspect ratio, the characteristis of frequency are very different, because the second shear layer is developed in the diffused first shear layer.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.5
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• pp.37-50
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• 2007

This study investigated the characteristics of spray generated by a liquid coaxial swirl injector used in a combustor of the liquid rocket engine. The linear stability analysis considered long and short wave was introduced in liquid sheet breakup. Through the hydrodynamic analysis the initial liquid sheet thickness spray angle and injection velocity were predicted. To evaluate the effect of turbulence model standard $k-{\varepsilon}$ and RNC $k-{\varepsilon}$ model were applied to numerical calculation and it was known that RNC $k-{\varepsilon}$ model was more applicable to predict spray characteristics. On the basis of this evaluation validation of the developed model was performed with swirl injector installed in LPRE and the predicted results of breakup length, spray angle, and SMD agreed well with experiments qualitatively and quantitatively.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.573-578
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• 2000

Flow through turbine flow meter is simulated by solving the incompressible Navier-Stockes equations. The solution method is based on the pseudocompressibility approach and uses an implicit-upwind differencing scheme together with the Gauss-Seidel line relaxation method. The equations are solved steadily in rotating reference frames and the centrifugal force and tile Coriolis force are added to the equation of motion. The standard $k-{\varepsilon}$ model is employed to evaluate turbulent viscosity. At first the stability and accuracy of the program is verified with the flow through a square duct with a $90^{\circ}$ bend and on the flat plate.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.7 no.2
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• pp.287-297
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• 1995

In this study, the geometry consists of a two-dimensional rectangular enclosure with localized heating from below. The size and the location of the heater on the floor has been varied, and one of the vertical walls remains at a low temperature simulating a cold window. The governing equations for momentum, energy and continuity, which are coupled with turbulent equations have been solved using a finite volume method. A low Reynolds number $k-{\varepsilon}$ model has been incorporated to solve the turbulent kinetic energy and the dissipation rate. The heat transfer characteristics and the thermal environmental characteristics of the room have been obtained for various system parameters in a room with a partially heated floor.