• Title, Summary, Keyword: Cell-centered scheme

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EVALUATION OF NUMERICAL APPROXIMATIONS OF CONVECTION FLUX IN UNSTRUCTURED CELL-CENTERED METHOD (비정렬 셀 중심 방법에서 대류플럭스의 수치근사벙법 평가)

  • Myong H.K.
    • Journal of computational fluids engineering
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    • v.11 no.1
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    • pp.36-42
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    • 2006
  • The existing numerical approximations of convection flux, especially the spatial higher-order difference schemes, in unstructured cell-centered finite volume methods are examined in detail with each other and evaluated with respect to the accuracy through their application to a 2-D benchmark problem. Six higher-order schemes are examined, which include two second-order upwind schemes, two central difference schemes and two hybrid schemes. It is found that the 2nd-order upwind scheme by Mathur and Murthy(1997) and the central difference scheme by Demirdzic and Muzaferija(1995) have more accurate prediction performance than the other higher-order schemes used in unstructured cell-centered finite volume methods.

A Numerical Simulation based on Cell-centered Scheme for Contractive and Dilative Motion on Axisymmetric Micro-hydro machine (셀중심법에 의한 축대칭 극소 로봇의 압축팽창운동에 대한 수치적인 연구)

  • 강효길;김문찬;전호환
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.2
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    • pp.90-97
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    • 2004
  • Flow mechanism of contractive and dilative motion is numerically investigated to obtain a propulsive force in highly viscous fluid. An axisymmetric code is developed with unstructured grid system based on cell-centered scheme. It is validated by comparing with the results of Stokes approximation for the problem of uniform flow past a sphere in low Reynolds number(R$_{n}$=1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. In order to investigate the grid dependency, two different grids are applied to the present computations. The present study provides key information for the development of an axisymmetric Micro-hydro-robot.t.

STUDY ON HIGH RESOLUTION SCHEMES SUITABLE FOR AN 3-D CFD CODE(POWERCFD) USING UNSTRUCTURED CELL-CENTERED METHOD AND INTERFACE CAPTURING METHOD (비정렬 셀 중심방법 및 경계면포착법을 사용하는 3차원 유동해석코드(PowerCFD)에 적합한 HR 해법에 관한 연구)

  • Myong, H.K.;Kim, J.E.
    • Journal of computational fluids engineering
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    • v.13 no.1
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    • pp.7-13
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    • 2008
  • Several high resolution schemes such as OSHER, MUSCL, SMART, GAMMA, WACEB and CUBISTA are comparatively studied with respect to the accurate capturing of fluid interfaces throughout the application to two typical test cases of a translation test and a collapsing water column problem with a return wave. It is accomplished by implementing the high resolution schemes in the in-house CFD code(PowerCFD) for computing 3-D flow with an unstructured cell-centered method and an interface capturing method, which is based on the finite-volume technique and fully conservative. The calculated results show that SMART scheme gives the best performance with respect to accuracy and robustness.

Analysis of Three-dimensional Cavity flow by using Unstructred grid (비정규 격자를 이용한 3차원 Cavity 유동 해석)

  • Kang, Hyo-Kil;Kim, Moon-Chan;Chun, Ho-Hwan
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.192-197
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    • 2003
  • Three-dimensional cavity flow is analyzed with the code by using unstructured grid. Incompressible Navier-Stokes equations are used as governing equations, and governing equations are discretized by Finite Volume Method. Artificial compressibility method, proposed by Chorin, and developed by Soh, is used for coupling a pressure and a velocity. Cell-centered scheme is adopted in the code, this has the effect of having denser grid than nodal scheme when the same grid is used. Weighted Averaging scheme is used for the value at a nodal point. Cavity flow is analyzed, and this computed results are compared with the results in the research report

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A Locally Linear Reconstruction scheme on arbitrary unstructured meshes (임의의 비정렬 격자계에서의 국지적 선형 재구성 기법)

  • Lee K. S.;Baek J. H.
    • 한국전산유체공학회:학술대회논문집
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    • pp.31-36
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    • 2003
  • A field reconstruction scheme for a cell centered finite volume method on unstructured meshes is developed. Regardless of mesh quality, this method is exact within a machine accuracy if the solution is linear, which means it has full second order accuracy. It does not have any limitation on cell shape except convexity of the cells and recovers standard discretization stencils at structured orthogonal grids. Accuracy comparisons with other popular reconstruction schemes are performed on a simple example.

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Iterative Cell-wise Solution Method for the Adaptive Analysis of a Meshless Method (무요소법의 적응해석을 위한 반복격자해법)

  • 석병호;임장근
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.607-614
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    • 2002
  • For the accurate analysis of crack problems, considerable nodal refinement near the crack tip to capture singular stress field with sufficient accuracy to provide a useful computation of stress intensity factor is required. So, in this paper, adaptive nodal refinement scheme is proposed where nodes in restricted cell regions centered at crack tip are arranged in array for enhanced spatial resolution and adaptivity. With only cell-wise adaptive refinement scheme around crack tip fields, singularity of crack tip is sufficiently described to expect a successive crack propagate direction. Through numerical tests, accuracy of the proposed adaptive scheme is investigated and compared with the finite element and experimental results. By this implementation, it is shown that high accuracy is achieved by using iterative cell-wise solution method fur analyzing crack propagation problems.

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Incompressible Viscous Analysis on Unstructured Meshes using Artificial Compressibility Method (가압축성 기법을 이용한 비정렬 격자상에서의 비압축성 점성해석)

  • Moon Young J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.113-117
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    • 1995
  • Viscous analysis on incompressible flows is performed using unstructured triangular meshes. A two-dimensional and axisymmetric incompressible Navier-Stokes equations are solved in time-marching form by artificial compressibility method. The governing equations are discretized by a cell-centered based finite-volume method. and a centered scheme is used for inviscid and viscous fluxes with fourth order artificial dissipation. An explicit multi-stage Runge-Kutta method is used for the time integration with local time stepping and implicit residual smoothing. Convergence properties are examined and solution accuracies are also validated with benchmark solution and experiment.

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Analysis for the Propulsion with Peristaltic Motion (Peristaltic 운동을 이용한 추진에 대한 연구)

  • 김문찬
    • Journal of the Society of Naval Architects of Korea
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    • v.39 no.4
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    • pp.11-16
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    • 2002
  • Flow mechanism of peristaltic motion is numerically and experimentally investigated to obtain a propulsive force in highly viscous fluid. Computing code for the analysis of the motions is developed with cell-centered unstructured grid scheme. The computed results by the developed code is compared with the experimental results which have been carried out to find out the propulsion mechanism in highly viscous fluid. The computed results shows good correlation with the experimental results and further the propulsive force can be obtained by sinusoidal motion which makes a pressure difference on waving surface. The more computation with variation of Reynolds number and parameters of motion is expected for finding a proper working range.

NUMERICAL STUDY ON TWO-DIMENSIONAL MULTIPHASE FLOWS DUE TO DENSITY DIFFERENCE WITH INTERFACE CAPTURING METHOD (경계면 포착법을 사용한 밀도차에 따른 다상유동에 관한 수치해석적 연구)

  • Myong, H.K.
    • 한국전산유체공학회:학술대회논문집
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    • pp.214-219
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    • 2007
  • Both the bubble rising in a fully filled container and the droplet splash are simulated by a solution code(PowerCFD). This code employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with interface capturing method (CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The present results are compared with other numerical solutions found in the literature. It is found that the present code simulate complex free surface flows such as multi phase flows due to large density difference efficiently and accurately.

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Calculation of Turbulent Flows Using an Implicit Scheme on Two-Dimensional Unstructured Meshes (2차원 비정렬 격자에서의 내재적 기법을 이용한 난류 유동 재산)

  • Kang Hee Jung;Kwon Oh Joon
    • Journal of computational fluids engineering
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    • v.2 no.2
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    • pp.26-34
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    • 1997
  • An implicit viscous turbulent flow solver is developed for two-dimensional geon unstructured triangular meshes. The flux terms are discretized based on a cell-centered formulation with the Roe's flux-difference splitting. The solution is advanced in time us backward-Euler time-stepping scheme. At each time step, the linear system of equation approximately solved wi th the Gauss-Seidel relaxation scheme. The effect of turbulence is with a standard k-ε two-equation model which is solved separately from the mean flow equation the same backward-Euler time integration scheme. The triangular meshes are generated advancing-front/layer technique. Validations are made for flows over the NACA 0012 airfoil. Douglas 3-element airfoil. Good agreements are obtained between the numerical result experiment.

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