• Title, Summary, Keyword: incompressible turbulent flow

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EVALUATION OF OPENFAOM IN TERMS OF THE NUMERICAL PRECISION OF INCOMPRESSIBLE FLOW ANALYSIS (OpenFOAM의 비압축성 유동 해석정밀도 평가)

  • Kim, Hyung Min;Yoon, Dong-Hyeog;Seul, Kwang-Won
    • Journal of computational fluids engineering
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    • v.18 no.2
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    • pp.49-55
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    • 2013
  • The goal of the research is to evaluate the open source code of OpenFOAM for the use of nuclear plant flow simulation objectively. Of the various incompressible flow solvers, simpleFoam, pimpelFoam are then tested under three validated cases (backward facing step, flow over circular cylinder and turbulent round jet flow). For the evaluation of steady state incompressible laminar flow simulation, low reynolds number of backward facing step flow was solved by simpleFoam. The resultant of the reattached lengths turned out to be similar with the other experimental and simulation results. For transient flow simulation, flow over circular cylinder and turbulent round jet flow were solved by pimpleFoam. The simulation accuracy was evaluated by comparing the resultant flow patterns with the description of the characteristics of the flow over the circular cylinder. The quantitative accuracy was evaluated for no more than 85% by comparing it to the decaying constants of the turbulent round jet velocity.

Efficient Computation of Turbulent Flow Noise at Low Mach Numbers Via Hybrid Method (하이브리드기법을 이용한 저마하수 난류소음의 효율적 전산해석)

  • Seo, Jung-Hee;Moon, Young-J.
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.9
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    • pp.814-821
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    • 2007
  • A hybrid method is presented for efficient computation of turbulent flow noise at low Mach numbers. In this method, the turbulent flow field is computed by incompressible large eddy simulation (LES), while the acoustic field is computed with the linearized perturbed compressible equations (LPCE) derived in this study. Since LPCE is computed on the rather coarse acoustic grid with the flow variables and source term obtained by the incompressible LES, the computational efficiency of calculation is greatly enhanced. Furthermore, LPCE suppress the instability of perturbed vortical mode and therefore secure consistent and stable acoustic solutions. The proposed LES/LPCE hybrid method is applied to three low Mach number turbulent flow noise problems: i) circular cylinder, ii) isolated flat plate, and iii) interaction between cylinder wake and airfoil. The computed results are closely compared with the experimental measurements.

Numerical Analysis of 3-D Turbulent Flows Around a High Speed Train Including Cross-Wind Effects (측풍영향을 고려한 고속전철 주위의 3차원 난류유동 해석)

  • Jung Y. R.;Park W. G.;Ha S. D.
    • Journal of computational fluids engineering
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    • v.1 no.1
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    • pp.71-80
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    • 1996
  • An iterative time marching procedure for solving incompressible turbulent flow has been applied to the flows around a high speed train including cross-wind effects. This procedure solves three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using first-order accurate schemes for the time derivatives and third/second-order accurate schemes for the spatial derivatives. Turbulent flows have been modeled by Baldwin-Lomax turbulent model. To validate present procedure, the flow around a high speed train at zero yaw angle was simulated and compared with experimental data. Generally good agreement with experiments was achieved. The flow fields around the high speed train at 9.2°, 16.7°, and 45° of yaw angle were also simulated.

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Incompressible Viscous Flow Analysis Around a Three Dimensional Minivan-Like Body (3차원 미니밴 형상 주위의 비압축성 점성 유동 해석)

  • Jung Y. R.;Park W. G.;Park Y. J.;Kim J. S.;Hong S. H.
    • Journal of computational fluids engineering
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    • v.2 no.1
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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.

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A Study on the Flow Characteristics Around an Axial Fan of Rotary Burner (로터리 버너의 축류형 팬 주위 유동특성 연구)

  • Ko, D.G.;Cho, D.J.;Yoon, S.J.
    • Journal of ILASS-Korea
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    • v.8 no.1
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    • pp.1-8
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    • 2003
  • The flow analysis of the axial fan of rotary burner was performed by SIMPLE(Semi Implicit Method for Pressure Linked Equations) algorithm and finite volume mothod performed in the case of 3-D, incompressible, turbulent flow. In this study, the coordinate transformation was adapted for the complex geometry of axial fan, and the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent flow. Multi-block grid system was used for flow field and divided into four domains such as the inlet, outlet, flow field of rotating vane, and tip clearance. Fan rotation was simulated by rotational motion using MRF(Multiple Rotating Reference Frame) in steady, incompressible state flow.

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Stabilized finite element technique and its application for turbulent flow with high Reynolds number

  • Huang, Cheng;Yan, Bao;Zhou, Dai;Xu, Jinquan
    • Wind and Structures
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    • v.14 no.5
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    • pp.465-480
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    • 2011
  • In this paper, a stabilized large eddy simulation technique is developed to predict turbulent flow with high Reynolds number. Streamline Upwind Petrov-Galerkin (SUPG) stabilized method and three-step technique are both implemented for the finite element formulation of Smagorinsky sub-grid scale (SGS) model. Temporal discretization is performed using three-step technique with viscous term treated implicitly. And the pressure is computed from Poisson equation derived from the incompressible condition. Then two numerical examples of turbulent flow with high Reynolds number are discussed. One is lid driven flow at Re = $10^5$ in a triangular cavity, the other is turbulent flow past a square cylinder at Re = 22000. Results show that the present technique can effectively suppress the instabilities of turbulent flow caused by traditional FEM and well predict the unsteady flow even with coarse mesh.

Incompressible Viscous Flow Analysis Around a Three Dimensional Minivan-Like Body (3차원 미니밴 형상 주위의 비압축성 점성 유동 해석)

  • Jung Y. R.;Park W. G.;Park Y. J.;Kim J. S.
    • 한국전산유체공학회:학술대회논문집
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    • pp.46-51
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    • 1996
  • 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. The fourth -order artificial damping is added to the continuity equation for numerical stability. A H-H type multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. The simulation shows three dimensional vortex-pair just behind body. And the flow separation is also observed the rear of the body. It has concluded that the results of present study properly agree with physical flow phenomena.

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Parallel Finite Element Simulation of the Incompressible Navier-stokes Equations (병렬 유한요소 해석기법을 이용한 유동장 해석)

  • Choi H. G.;Kim B. J.;Kang S. W.;Yoo J. Y.
    • 한국전산유체공학회:학술대회논문집
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    • pp.8-15
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    • 2002
  • For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message Passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Wavier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen fur the modeling of small eddies in turbulent flows. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. Then, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at $Re = 2.6\times10^6$, which is based on the model height and inlet free stream velocity, using 32 processors on IBM SMP cluster and compared with the existing experiment.

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Modeling wind ribs effects for numerical simulation external pressure load on a cooling tower of KAZERUN power plant-IRAN

  • Goudarzi, Mohammad-Ali;Sabbagh-Yazdi, Saeed-Reza
    • Wind and Structures
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    • v.11 no.6
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    • pp.479-496
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    • 2008
  • In this paper, computer simulation of wind flow around a single cooling tower with louver support at the base in the KAZERUN power station in south part of IRAN is presented as a case study. ANSYS FLOTRAN, an unstructured finite element incompressible flow solver, is used for numerical investigation of wind induced pressure load on a single cooling tower. Since the effects of the wind ribs on external surface of the cooling tower shell which plays important role in formation of turbulent flow field, an innovative relation is introduced for modeling the effects of wind ribs on computation of wind pressure on cooling tower's shell. The introduced relation which follows the concept of equivalent sand roughness for the wall function is used in conjunction with two equations ${\kappa}-{\varepsilon}$ turbulent model. In this work, the effects of variation in the height/spacing ratio of external wind ribs are numerically investigated. Conclusions are made by comparison between computed pressure loads on external surface of cooling tower and the VGB (German guideline for cooling tower design) suggestions.