• Wind and Structures
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• 제5권2_3_4호
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• pp.89-100
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• 2002

Accidental gaseous losses from industrial processes can pose considerable health and environmental risks but assessing their health, safety and environmental impact is problematic. Improved understanding and simulation of the dispersion of emissions in the vicinity of storage tanks is required. The present study aims to assess the capability of the turbulence closures and meshing alternatives in a commercially available CFD code for predicting dispersion in the vicinity of cubes and circular cylindrical storage tanks. The performance of the $k-{\varepsilon}$ and Reynolds Stress turbulence models and meshing alternatives for these cases are compared to experimental data. The CFD simulations are very good qualitatively and, in many cases, quantitatively. A mesh with prismatic elements is more accurate than a tetrahedral mesh. Overall the Reynolds stress model performs slightly better than the $k-{\varepsilon}$ model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.723-728
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• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-e two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.159-162
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• 2007

The numerical efforts are presented for investigation of irregular waves passing a slit cassion and a warock block breakwater. In the numerical model, the Reynolds equations are solved by a finite difference method and $k-\varepsilon$ model is employed for the turbulence analysis. To track the free surface displacement, the volume of fluid method(VOF) is employed. Numerical predictions of reflection and transmission coefficients are compared with those of the warock block breakwater with the slit caisson. Energy dissipation and seawater exchange rates of the slit caisson are better than those of the warock block breakwater.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.126-131
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• 2004

Pressure-based 알고리듬을 기반으로 한 cavitation 현상의 수치해석 코드를 개발하였다. Wall function을 사용한 k-\varepsilon$ 난류모델을 사용하였으며, cavitation 모델에는 volume transport equation을 사용하였다. 유동장은 저속이기 때문에 압축성 효과는 고려하지 않았다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.85-88
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• 2010

본 연구에서는 액체로켓 분사기에서 임계압력 이상의 추진제의 혼합과 연소과정을 수치적으로 모사하여 분석하고자 하였다. 이 과정에서 확장된 $k-{\varepsilon}$ 난류 모델을 이용하여 난류 속도장을 예측하였고 고압에서의 실제 유체 효과를 고려하기 위하여 혼합 추진제의 물성치는 SRK 상태 방정식을 이용하여 계산하였다. 또한 난류 확산 화염에서의 좀 더 정확한 난류와 화학반응의 상호작용을 고려하기 위하여 실제 유체 효과를 고려할 수 있는 층류 화염편 모델을 이용하였다. 수치적인 계산을 바탕으로 이상기체 가정을 사용한 결과와 비교하여 실제 유체의 효과와 기체메탄/액체산소 동축 전단 분사기의 제트화염 구조를 상세하게 살펴보았다.

• 동력기계공학회지
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• 제16권2호
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• pp.17-23
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• 2012

The steady three-dimensional computational thermal flow analysis using standard k-${\varepsilon}$ turbulence model was carried out to investigate the heat transfer characteristics of a cabin cooler for a commercial vehicle. The heat exchanging method of this cabin cooler is to use the cooling effect of a thermoelectric module. In view of the results so far achieved, the air system resistance of a cabin cooler is about 12.4 Pa as a static pressure, and then the operating point of a cross-flow fan considering in this study is formed in the comparatively low flowrate region. The air temperature difference obtained from the cold part of an thermoelectric module is about $26^{\circ}C$, and the cooling water temperature difference obtained from the hot part of an thermoelectric module is about $3.5^{\circ}C$.

• 동력기계공학회지
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• 제16권5호
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• pp.47-54
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• 2012

The steady three-dimensional numerical analysis on the thermal flow using standard k-${\varepsilon}$ turbulence model was carried out to investigate the air cooling effect of a cooler on the cabin for a commercial vehicle. Here, the heat exchanging method of this cabin cooler uses the cooling effect of a thermoelectric module. In consequence, the air system resistance of a cooler within the cabin is about 12.1 Pa as a static pressure, and then the operating point of a virtual cross-flow fan considering in this study is formed in the comparatively low flowrate region. The discharging air temperature of a cooler is about $14{\sim}15^{\circ}C$. Moreover, the air cooling temperature difference obtained under the outdoor cabin temperature of $40^{\circ}C$ shows about $7{\sim}9^{\circ}C$ in a driver resting space and about $9{\sim}14^{\circ}C$ in the front of a driver's seat including the space of a driver's foot.

• 한국화재소방학회논문지
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• 제28권4호
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• pp.35-43
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• 2014

3개의 난류모델과 3개의 연소모델로 구성된 9개의 모델조합을 이용하여 난류 부분예혼합 제트화염 구조에 대한 수치적 예측성능을 검토하였다. 이용된 난류모델은 표준 ${\kappa}-{\varepsilon}$ 모델(SKE), Realizable ${\kappa}-{\varepsilon}$ 모델(RKE) 및 Reynolds 응력모델(RSM)이며 연소모델들은 Eddy Dissipation Concept 모델(EDC), Steady Laminar Flamelet 모델(SLF)와 Unsteady Laminar Flamelet 모델(ULF)이다. 9개 모델조합의 예측성능을 평가하기 위하여 실험결과가 알려진 Sandia D 화염인 난류 부분예혼합 제트화염을 대상으로 수치계산을 수행하였다. 얻어진 결과로서, 화염길이의 예측은 RSM > SKE > RKE순으로 길게 예측하였으며, RKE 난류모델은 화염길이를 너무 과소 예측하는 것을 확인하였다. RSM + SLF과 RSM + ULF의 조합은 화염길이는 비교적 잘 예측하였지만 하류에서의 화염온도를 과대 예측하였다. 반면에 SKE와 연소모델의 조합에서 SLF 또는 ULF 조합은 화염길이 뿐만 아니라 하류에서의 화염온도도 비교적 잘 예측하였는 것을 확인하였다. 반경방향 화염온도 및 화학종 농도분포를 비교해 본 결과 SKE와 연소모델의 조합이 가장 예측성능이 뛰어났으며 SKE + ULF의 조합이 가장 우수한 예측성능을 갖는 것을 확인하였다.

• 한국산업보건학회지
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• 제10권2호
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• pp.140-149
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• 2000

In industrial field, there are several operations where a horizontal unidirectional airflow is used to control airborne contaminants. When a worker is immersed in a uniform freestream, a recirculating airflow can be created downstream of the worker by the phenomenon of boundary layer seperation. If the contaminant source and the breathing zone are within this near-wake region, high exposure may occur. The investigation for the effect of contaminant source location on worker exposure was performed by using CFD(Computational Fluid Dynamics). The airflow field was numerically calculated by assuming a steady flow and using the standard $k-{\varepsilon}$ turbulence model. As the results were compared with experimental data, the applicability of CFD was successfully verified. Subsequently, the breathing zone concentrations of the worker were predicted and compared with experimental data. The effects of contaminant density and turbulence intensity of freestream on worker exposure were evaluated.

• 한국전산유체공학회지
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• 제8권2호
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• pp.8-15
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• 2003

Three nonlinear κ-ε models with the wall function method are applied to the fully developed turbulent flow in a triangular subchannel of a bare rod bundle. Typical predicted quantities such as axial and secondary velocities, turbulent kinetic energy and wall shear stress are compared in details both qualitatively and quantitatively with both each other and experimental data. The nonlinear κ-ε models by Speziale[1] and Myong and Kasagi[2] are found to be capable of predicting accurately noncircular duct flows involving turbulence-driven secondary motion. The nonlinear κ-ε model by Shih et aL.[3] adopted in a commercial code is found to be unable to predict accurately noncircular flows with the prediction level of secondary flows one order less than that of the experiment.