• 한국추진공학회지
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• 제1권1호
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• pp.73-81
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• 1997

질량가중평균의 완전 Wavier-Stokes 방정식, 압축성 난류유동에 대한 Morkovin의 가설, $\textsc{k}$-$\varepsilon$ 난류모델, 압력구배와 벽열전달과 압축성의 효과를 고려한 벽함수 모델, Karki의 수치해석기법 등을 사용하여 로켓노즐 내의 난류유동 및 열 전달을 수치해석하고 Back 등의 실험 결과와 비교하였다.

• Journal of Mechanical Science and Technology
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• 제17권7호
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• pp.1054-1062
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• 2003

The numerical simulations of flow and pollutant particle dispersion are described for two-dimensional bell shaped hills with various aspect ratios. The Reynolds-averaged incompressible Navier-Stokes equations with low Reynolds number $\kappa$-$\varepsilon$ turbulent model are used to simulate the flowfield. The gradient diffusion equation is used to solve the pollutant dispersion field. The code was validated by comparison of velocity, turbulent kinetic energy, Reynolds shear stress, speed-up ratio, and ground level concentration with experimental and numerical data. Good agreement has been achieved and it has been found that the pollutant dispersion pattern and ground level concentration have been strongly influenced by the hill shape and aspect ratio, as well as the location and height of the source.

• Journal of Ship and Ocean Technology
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• 제5권2호
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• pp.27-48
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• 2001

Turbulent flow calculations are performed for the two modern practical VLCCs with the sable forebody and the slightly different afterbody, i.e. KVLCC and KVLCC2. Three $\textsc{k}-\varepsilon$ turbulence models are tested to investigate the differences caused by the turbulence models. The calculated results around the two VLCC hull forms using O-O grid topology and profile-fitted surface meshes are compared to the measured data from towing tank experiment. The realizable $\textsc{k}-\varepsilon$model provided realistic wake distribution with hook-like shape, while the standard and RNG-based $\textsc{k}-\varepsilon$models failed. It is very encouraging to see that the CFD with relatively simple turbulence closure can tell the difference quantitatively as well as qualitatively for the two hull forms with stern frameline modification.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.253-256
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• 1999

The Streamline Upwind Petrov-Galerkin(SUPG) finite element method is used to solve the two-dimensional laminar and turbulent flow. The flow is simulated by averaged Navier-Stokes equations with a penalty function approach and the lograithmic(k-$\varepsilon$) turbulent model is employed to take into account its turbulent behavior. The near-wall viscous sub-layer model is employed to approach the dominant viscous effects in the near wall zones. To find a good-enough initial guess of the Newton-Raphson iteration solving Nonlinear Matrix the Incremental method is considered for momentum and the Incomplete logarithmic turbu-lent equations for Turbulence. The validation of our method is investigated in comparision with published experimental data.

• 한국해안해양공학회지
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• 제5권2호
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• pp.91-98
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• 1993

본고는 정상류 가로흐름이 존재하는 천해역으로 방출되는 온수의 거동 예측을 위한 2차원 난류모형 개발을 기술한다. 모델 기본방정식은 수심적분된 연적 및 운동방정식, 에너지보존 방정식이 사용되며, SIMPLE로 알려진 교치기법으로 적분된다. 난류운동량 및 열확산항은 2차원 $ extsc{k}$-$\varepsilon$ 방정식으로부터 결정된다. 기존 실험결과와의 비교에서 천수역 Near-field 해역내 난류현상 재현에 유망한 기법임이 확인되었다.

• 설비공학논문집
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• 제11권6호
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• pp.766-773
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• 1999

A numerical analysis has been performed solidification problem using the fixed grid-enthalpy method with enthalpy-porosity relation. A modified standard $k-\varepsilon$ model was applied to describe the influence of turbulent flow. Computational procedures are based on the finite volume method and the non-staggered grid system. Comparisons with the different three experimental results show that applying a modified standard $k-\varepsilon$model in mushyzone is better than the previous computation results. This paper includes another EMBR's influences such as change of velocity field, Increasement of temperature and dispersion of flow out of nozzle into the flow field. These EMBR's influences are compared to case without EMBR.

• 한국해안해양공학회지
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• 제15권2호
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• pp.80-85
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• 2003

본 연구에서는 Reynolds 방정을 지배방정식으로 하고 난류 해석을 위해 k-$\varepsilon$모델을 사용하였으며, 자유수면 변위를 추적하기 위해 VOF기법을 사용한 수치해석 모델을 이용하여 다양한 주기를 갖는 크노이드파의 발생과 최대 처오름높이에 대해 알아보았다. 발생된 크노이드파의 파형은 해석해와 매우 잘 일치하였다 또한, 계산된 최대 처오름높이를 수리모형실험의 관측 값과 비교해 본 결과는 경계요소법에 의한 수치해보다 높은 정확도를 나타내었다.

• 한국수자원학회논문집
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• 제50권2호
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• pp.89-97
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• 2017

만곡수로에서의 흐름 구조는 나선형 운동을 갖는 이차 재순환 흐름 그리고 만곡부 측벽으로부터 발생하는 흐름분리로 인한 전단층 등으로 복잡하다. 이 연구에서는 3개의 통계학적 난류모형($k-{\varepsilon}$, RNG $k-{\varepsilon}$, $k-{\omega}$ SST) 그리고 자유수면 변동 해석을 위한 VOF 기법을 적용한 비정상 Reynolds-averaged Navier-Stokes (RANS) 계산을 수행하여 고진폭 만곡수로인 키노시타(Kinoshita) 수로에서의 이차류와 편수위를 해석하였다. 2차 정확도의 유한체적법을 이용하여 구한 해석결과를 기존 수리실험 자료와 비교하여 각 난류모형의 적용성을 평가하였다. 비정상 RANS 계산에서 적용한 3개의 통계학적 난류모형의 해석 결과를 분석해 보면 키노시타 수로에서 발생하는 만곡부 편수위는 3개 모형 모두 유사하게 모의하는 한편, 전반적인 이차류 분포는 $k-{\omega}$ SST상대적으로 잘 모의하는 것으로 나타났다. 하류에 위치한 만곡부 흐름에 영향을 미쳐 국부적으로 발생한 이차류와 이전의 만곡부 중앙 수면 부근에서 발생하는 한 쌍의 이차 와류가 존재하는 현상을 관측하였으며, $k-{\omega}$ SST 난류모형은 이러한 복잡한 와류 변화를 양호하게 모의했다. $k-{\varepsilon}$ 모형을 기반으로 개발된 두 모형으로 모의한 결과에서는 실험에서 관측된 중앙 만곡부에 존재하는 두 개의 이차류 중, 시계방향 와류가 재현되지 않는다. VOF기법을 이용해서 계산한 만곡부에서의 편수위 해석결과는 적용한 모든 난류모형에 대해서 전반적으로 실험값을 양호하게 재현하는 것으로 나타났다.

• 설비공학논문집
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• 제10권5호
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• pp.535-549
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• 1998

A numerical study for performance analysis of a counterflow type forced draft tower and natural draft cooling tower has been performed based on the method using the finite volume method with non-orthogonal body fitted and non-staggered grid system. For solving the coupling problem between water and air, air enthalpy balance, moisture fraction balance, water enthalpy balance, and water mass balance equations are solved with Navier-Stoke’s equations simultaneously. For the effect of turbulence, the standard k-$\varepsilon$ turbulent model is implied in this analysis. The predicted result of the present analysis is compared with the experimental data and the commercial software result to validate the present study, The predicted results show good agreement with the experimental data and the commercial software result. To investigate the influence of the cooling tower design parameters such as approach, range and wet bulb temperature, parametric studies are also peformed.

• 한국산업보건학회지
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• 제15권3호
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• pp.239-249
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• 2005

Ventilation effect is analyzed for boiler building with multiple heat sources. Air flow inside the boiler building is characterized as turbulent mixed convection. Analysis methodology is set up with two different $k-{\varepsilon}$ type models (standard $k-{\varepsilon}$, RNG $k-{\varepsilon}$). Two different cases with high and low outside temperature are analyzed. In case of high outside temperature condition, mixed convection is well realized inside the boiler building. With different upper louver opening rate, air flow is also well established and proper opening rate is found to meet design limit in case of low outside temperature condition. Difference of analysis results for two different turbulence models are not significant. Therefore, analysis methodology with simple $k-{\varepsilon}$ turbulence model is found to be reliable for the boiler building ventilation analysis. However, more simplified geometrical model is desired to expand its application.