• 대한조선학회논문집
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• 제28권1호
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• pp.19-26
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• 1991

난류유동 지배 방정식인 타원형 레이놀즈 방정식을 수치계산에 의해 계산하였다. 계산 대상으로는 실험결과가 많이 알려진 축 대칭 물체를 택하였다. 수치적으로 얻어지는 물체접합 좌표계를 사용하였고, 난류모형으로는 $\kappa-\varepsilon$모형으로써 경계면 근처의 복잡한 유동특성을 추정할 수 있도록 영역을 2개로 나누어 계산하는 2층모형(two-layer model)을 사용하였다. 입구면의 경계조건을 사용하여 물체의 중앙부 이후부터 계산을 수행하였다. 입구면에서의 속도와 난류량 등은 경계층 방정식을 풀어 얻어진 결과와 평판의 경계층 자료로부터 얻어진 결과를 사용하였으며, 이로부터 입구면 조건이 점성유동 해석 결과에 미치는 영향을 조사하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.729-731
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• 2008

Three-dimensional unsteady simulation using RNG $\kappa-\varepsilon$ turbulence model is used in full flow passage of model Kaplan turbine. Then the pressure pulsation is obtained. Monitoring data of pressure pulsation in the turbine is obtained through experiment and is compared with the numerical simulation. And a good coherence is shown between the simulation and the experiment. Then the regularity of the pressure pulsation s distribution and transmission in the turbine is discussed in detail.

• 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.

• 한국해양공학회지
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• 제14권4호
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• pp.9-16
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• 2000

This paper deals with the numerical and experimental study on the characteristics of the flow around a sunken vessel. Numerical simulation of the two dimensional steady flow on the midship section are carried out by the CFD code which is developed by using finite volume method and which includes the standard $textsc{k}$-$\varepsilon$ model with standard wall function. A experimental study is also carried out for the 1/100 scale model in circulating water channel. A velocity fields around the ship are measuremed by using particle image velocimetry technique. And the fluid forces acting on the ship hull by uniform current are measured by two axis load cell. The computed and measured velocity fields on the midship section are compared with each other in the view point of velocity dstribution and reattachement length, which shows good agreement in quality. The drag force on the vessel also showed the same tendency in both computational and experimental results. However, the quantitative disagreements are shown due to the three dimensional effect of the experiment. The result are used to determine the functional efficiency and stability of the vessel as a artificial reef.

• 한국산업보건학회지
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• 제8권2호
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• pp.163-177
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• 1998

Computational Fluid Dynamics(CFD) was applied to predict air flow around the hoods : circular hoods, square hoods, and push-pull hoods. A commercially available CFD software, CFD-ACE(Ver. 4.0), was tested, which is based on the finite volume method using the ${\kappa}-{\varepsilon}$ turbulence model. Numerical results were compared with the experimental, analytical and numerical results from other studies. CFD solutions showed an excellent agreement with the previous experimental and numerical results. It is promising that CFD techniques could be applied on the variety of complex problems in the industrial ventilation engineering.

• 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.

• Wind and Structures
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• 제1권3호
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• pp.271-284
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• 1998

This paper uses the numerical simulation to investigate the interference effect of 3-D turbulent flow around two high rise buildings in proximity at the different relative heights, gaps, and wind velocities. The computer program used to carry out the simulation is based on the control volume method and the SIMPLEST algorithm. The ${\kappa}-{\varepsilon}$ model was used to simulate turbulence effects. Since the contracted flow between two adjacent buildings enhances the strength of vortex shedding from the object building, the pressure coefficient on each side wall of the object building is generally increased by the presence of apposed building. The effect is increased as the relative height or the gap between the two buildings decreases. The velocity on the vertical center line between two buildings is about 1.4 to 1.5 times the upstream wind velocity.

• 대한기계학회논문집
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• 제13권5호
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• pp.1052-1060
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• 1989

본 연구에서는 0-방정식 난류모형과 2-방정식 난류모형 그리고 역압력 구배와 수렴과 발산의 영향을 고려한 2-방정식 난류모형을 사용하여 대칭단면에서의 난류유동 을 해석하고, 계산 결과를 비교하여 난류모형의 적절성을 평가하고자 한다.

• 한국산학기술학회논문지
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• 제6권4호
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• pp.302-308
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• 2005

구조가 복잡한 챔버의 온도분포와 유속변화를 연구하였다. 압축성 혹은 비압축성 유체, 층류 혹은 난류의 유속변화를 모델링 할 수 있는 FLUENT 프로그램으로 모사실험을 하였다. 챔버의 구조는 매우 복잡하여 단순화한 구조를 표준 $\kappa-\varepsilon$ 모델과 RNG $\kappa-\varepsilon$ 난류 모델 모사 실험하였다. 평가지역의 온도편차가 적은 것이 중요하다. 본 연구에서 얻은 챔버 내부의 온도분포와 유속변화 자료를 챔버의 제어 알고리즘을 향상하는 제공하였다. 개선된 제어 알고리즘을 이용하여 실제계에 적용한 결과 평가지역의 온도편차가 매우 개선되었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.385-390
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• 2003

Shape of a multi-blades centrifugal fan is optimized by response surface method based on three-dimensional Navier-Stokes analysis. For numerical analysis, Reynolds-averaged Wavier-Stokes equations with standard $k-{\varepsilon}$ turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Optimizations with and without constraints are carried out. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. The correlation of efficiency with relative size of inactive zone at the exit of impeller is discussed as well as with average momentum fluxes in the scroll.