• 한국자동차공학회논문집
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• 제11권2호
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• pp.126-133
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• 2003

The aerodynamic characteristics of automobiles have received substantial interest recently. Detailed knowledge of the vehicle aerodynamics is essential to improve fuel efficiency and enhance stability at high-speed cruising. In this study, a numerical simulation has been carried out for three-dimensional turbulent flows around a commercial bus body. Also, the effect of rear-spoiler attached at rear end of bus body was investigated. The Wavier-Stokes equation is solved with SIMPLE method in general curvilinear coordinates system. RNG $k-\varepsilon$ turbulence model with the MARS scheme was used for the evaluating aerodynamic forces, velocity and pressure distribution. The results showed details of the three-dimensional wake flow in the immediate rear of bus body and the effect of rear-spoiler on the wake structure. A maximum of 14% reduction in drag coefficient was achieved for a model with a rear-spoiler.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2011년도 추계학술논문발표회 논문집
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• pp.15-18
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• 2011

본 연구는 국내 FDS연구동향 및 적용사례를 분석한 것으로서, 분석한 결과 FDS는 법의 개정 및 화재사고와 밀접한 관계를 가지는 것으로 판단되었다. 또한 FDS 수치해석시의 격자 민감도, 벽면의 난류유동 등의 문제점이 파악되어, 향후 개선되어야 할 것으로 판단된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.303-306
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• 2007

고고도 모사용 초음속 디퓨져의 설계 및 작동인자에 대한 영향을 파악하기 위하여 압축성 축대칭 Wavier-Stokes 방정식 기반의 two-layer k-$\varepsilon$ 난류 수치해석과 실험 결과를 비교 분석하였다. 디퓨져의 설계 및 작동인자인 노즐과 디퓨져의 면적비, 진공챔버의 크기, 제트의 공급압력에 대한 디퓨져내 유동 발달과 디퓨져 작동 특성을 살펴보았다.

• 설비공학논문집
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• 제17권9호
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• pp.799-807
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• 2005

The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

• 설비공학논문집
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• 제3권1호
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• pp.11-25
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• 1991

The steady, incompressible developing 3-dimensional turblent flow in a square sectioned curved duct has been investigated by using partially-parabolic equation and Finite Analytic Method. The calculation of turbulent flow field is performed using 2-equation K-$\epsilon$ turbulence model, modified wall function, simpler algorithm and numerically generated body fitted coordinates. Iso-mean velocity contours at the various sections are compared with the existing experimental data and elliptic solutions by other authors. In the region of $0^{\circ}<{\theta}<71^{\circ}$, present results agree with the experimental data much better than the elliptic solution for the similar number of grid points. Furthermore, for the same tolerance, the present solution converges four times faster than the elliptic solution.

• 설비공학논문집
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• 제7권3호
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• pp.382-395
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• 1995

A numerical study has been performed on flow characteristics in a domestic refrigerator whose size is $540mm{\times}1,530mm{\times}680mm$, considering existence of a fan and evaporator. The flow field has been simulated with the low Reynolds number $k-\bar{\varepsilon}$ turbulent model and SIMPLE algorithm based on the finite volume method. The region of fan which makes driving force for cold air distribution was modeled as a region in which momentum sources are generated uniformly. The concept of the distributed pressure resistance was applied to describe the momentum loss from evaporator. The result showed that the rate of cold air distribution into freezing room and cold storage room was almost 7 : 3.

• 설비공학논문집
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• 제3권3호
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• pp.186-196
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• 1991

Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.

• 한국전산유체공학회지
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• 제7권1호
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• pp.20-27
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• 2002

Flow over a circular cylinder is studied numerically using a turbulence model. Based on the κ-ε-f/sub μ/ model of Park and Sung[6], a new damping function is used. The efficiency of the strain dependent damping function is addressed for vortex-shedding flows past a circular cylinder. The mean velocity and Reynolds stresses are compared with available experimental data at Re/sub D/= 3900. Also, the computational results for the Strouhal number are evaluated at several Reynolds number. The predictions by κ-ε-f/sub μ/ model are in good agreement with the experiments.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.79-87
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• 2002

The present work analyzed the effect of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly, by obtaining velocity and pressure fields, turbulent intensity, flow-mixing factors, heat transfer coefficient and friction factor using three-dimensional RANS analysis. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ model is used as a turbulence closure model, and, periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant, but the twist angle of mixing vane is changed. The results with three turbulence models( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 추계 학술대회논문집
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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.