• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.9-18
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• 1999

The present study is aimed to investigate flow characteristics of two-dimensional backward-fac-ing step by numerical approach. A convection conservation difference scheme based upon SOLA algorithm is used for the solution of the two-dimensional incompressible Navier-Stokes equations to simulate the laminar transitional and trubulent flow conditions at which the experimental data can be available for the backlward-facing step. The twenty kinds of reynolds number are used for the calculations. In an effort to demonstrate that the reported solutions are dependent on the mesh refinement computations are performed on seven different meshes of uniformly increasing refinement. also to investigate the result of inflow dependence two kinds of the inflow profile are chosen for the laminar flow. Irregular grid is adopted to minimize the errors on the satis-faction fo the discretized continuity. As criterion of benchmarking the result of numerical simula-tion reattachment lengthis used for the selected Reynolds numbers. The results of the present study prove the fact that the numerical predictions agree well with the experimental data and the flow characteristics are shown at the backward-facing step.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.438-444
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• 2015

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

• 대한기계학회논문집
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• 제16권10호
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• pp.1971-1978
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• 1992

본 연구에서는 원형 파이프에 원추형 디퓨져가 연결된 덕트 내의 유동장에 대 하여 Launder-Sharma의 저 레이놀즈수 k-.epsilon. 난류모델을 이용하여 수치해석을 수행하였 으며, 수치해석 방법으로는 타원형 방법을 사용하였으며, 앞으로 일반적인 단면의 곡 관이나 스크롤 내부 유동 등의 연구 수행을 감안하여 지배방정식을 일반 비직교 좌표 계로 변환하여 계산을 수행하였다.

• 한국전산유체공학회지
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• 제2권1호
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• pp.46-53
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• 1997

The flow field around a three dimensional minivan-like body has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. A H-H type of multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. To validate present procedure, the flows around the Ahmed body with 12.5° of slant angle are simulated. A good agreement with other numerical results is achived. After code validation, the flows around a mimivan-like body are simulated. The simulation shows three dimensional vortex-pair just behind body. The flow separation is also observed on the rear of the body. It has concluded that the results of present study properly agreed with physical flow phenomena.

• 한국전산유체공학회지
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• 제12권2호
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• pp.21-25
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• 2007

A general purpose program NUFLEX has been extended for two-phase flows with topologically complex interface and cavitation flows with liquid-vapor phase change caused by large pressure drop. In analysis of two-phase flow, the phase interfaces are tracked by employing a LS(Level Set) method. Compared with the VOF(Volume-of-Fluid) method based on a non-smooth volume-fraction function, the LS method can calculate an interfacial curvature more accurately by using a smooth distance function. Also, it is quite straightforward to implement for 3-D irregular meshes compared with the VOF method requiring much more complicated geometric calculations. Also, the cavitation process is computed by including the effects of evaporation and condensation for bubble formation and collapse as well as turbulence in flows. The volume-faction and continuity equations are adapted for cavitation models with phase change. The LS and cavitation formulation are implemented into a general purpose program for 3-D flows and verified through several test problems.

• 대한조선학회논문집
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• 제34권2호
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• pp.39-47
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• 1997

본 연구에서는 수치계산을 동하여 선체-부가물 주위의 난류유동을 해석하였다. 지배방정식으로는 Navier-Stokes방정식과 연속방정식을 사용하였으며, 선체 및 부가물의 3차원 형상을 정도 높게 표현하기 위하여 물체적합좌표계 (Body-Fitted Coordinate System)를 도입하였다. 지배방정식들은 유한체적법 (Finite Volume Method)을 이용하여 이산화 하였으며, 난류모형으로는 SGS (Sub-Grid Scale)모형을 사용하였다. 계산 대상 선형으로 실험 및 계산 자료가 많은 Wigley선형을 선택하고, $Rn=1.0{\times}10^6$인 경우에 대하여 계산을 수행하여 부가물이 선체 주위의 난류유동에 미치는 영향을 예측할 수 있음을 보였다.

• 한국해양공학회지
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• 제23권1호
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• pp.38-42
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• 2009

Recently, various particle based simulation techniques, which solve the Navier Stokes and continuity equations, have been developed and applied to complicated engineering problems. However, although progress is being made on their visualization or rendering techniques, these are still insufficient. In this study, to render a smooth configuration for a free surface, a rendering technique was developed that included the generation of density fields from the location information for simulated particles and the creation model for a polygonal surface. The developed rendering technique was applied to the visualization of a dynamic free surface flow interacting with a structure using a particle based simulation technique.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1265-1272
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• 2011

원형 용기에서 전자기력에 의해 구동되는 전해질 유체의 순환유동을 구하기 위해 연속 방정식, 운동량 방정식에 대한 수치해석을 수행하였다. 그리고 실험을 병행하여 기초 데이터를 마련하고, 실험과 수치해석 결과가 정성적, 정량적 면에서 상당히 일치한 것을 확인하였다. 또 몇 가지 실험인자 값을 바꿔가며 실험과 수치해석을 반복 수행한 결과 전해질 농도가 클수록, 수심이 얕을수록, 자기장이 클수록, 교류 진동수가 작을수록 유속이 빨라지는 등 각각의 인자가 미치는 영향을 알 수 있었다.

• 대기
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• 제21권1호
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• pp.95-108
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• 2011

The effects of an apartment complex on flow and pollutant dispersion in an urban area are numerically investigated using a computational fluid dynamics (CFD) model. The CFD model is based on the Reynolds-averaged Navier-Stokes equations and includes the renormalization group k-${\varepsilon}$ turbulence model. The geographic information system (GIS) data is used as an input data of the CFD model. Eight numerical simulations are carried out for different inflow directions and, for each inflow direction, the effects of an apartment complex are investigated, comparing the characteristics of flow and dispersion before and after construction of the apartment complex in detail. The observation data of automatic weather system (AWS) is analyzed. The windrose analysis shows that the wind speed and direction after the construction of the complex are quite different from those before the construction. The construction of the apartment complex resulted in the decrease in wind speed at the downwind region. It is also shown that the wind speed increased partially inside the apartment complex due to the channeling effect to satisfy the mass continuity. On the whole, the wind speed decreased at the downwind region due to the drag effect by the apartment complex. As a result, the passive pollutant concentration increased (decreased) near the downwind region of (within) the apartment complex compared with that before the construction.

• Water Engineering Research
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• 제2권3호
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• pp.179-185
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• 2001

The time consuming and expensive nature of experimental research on scouring processes caused by flowing water makes it attractive to develop numerical tools for the predication of the interaction of the fluid flow and the movable bed. In this paper the numerical simulation of scour by a wall jet is presented. The flow is assumed to be two-dimensional, and the alluvium is cohesionless. The solution process, repeated at each time step, involves simulation of a turbulent wall jet flow, solution of the convection-diffusion of sand concentration, and prediction of the bed deformation. For simulation of the jet flow, the governing equations for momentum, mass balance and turbulent parameters are solved by the finite volume method. The SIMPLE scheme with momentum interpolation is used for pressure correction. The convection-diffusion equation is solved for sediment concentration. A boundary condition for concentration at the bed, which takes into account the effect of bed-load, is implemented. The time rate of deposition and scour at the bed is obtained by solving the continuity equation for sediment. The shape and position of the scour hole and deposition of the bed material downstream of the hole appear realistic.