• Title/Summary/Keyword: cell-centered finite

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NUMERICAL BEHAVIOR OF VERTEX-CENTERED AND CELL-CENTERED FINITE-VOLUME METHODS ON UNSTRUCTURED MESHES (비정렬 격자계에서 격자점 중심과 격자 중심 유한체적법의 수치적인 거동에 관한 비교 연구)

  • Kim, J.S.;Lee, H.D.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2006.10a
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    • pp.57-60
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    • 2006
  • This paper presents an assessment of vertex-centered and cell-centered finite-volume methods on unstructured meshes. The results indicate that the vertex-centered method is more reliable than the cell-centered method.

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A NEW NUMERICAL APPROXIMATION OF DIFFUSION FLUX IN UNSTRUCTURED CELL-CENTERED METHOD (비정렬 셀 중심 방법에서 확산플럭스의 새로운 수치근사방법)

  • Myoung H.K.
    • Journal of computational fluids engineering
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    • v.11 no.1 s.32
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    • pp.8-15
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    • 2006
  • The existing approximations of diffusion flux in unstructured cell-centered finite volume methods are examined in detail with each other and clarified to have indefinite expressions in several respects. A new numerical approximation of diffusion flux at cell face center is then proposed, which is second-order accurate even on irregular grids and may be easily implemented in CFD code using cell-centered finite volume method with unstructured grids composed of arbitrary convex polyhedral shape.

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 s.32
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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.

Development of a Flow Analysis Code Using an Unstructured Grid with the Cell-Centered Method

  • Myong, Hyon-Kook;Kim, Jong-Tae
    • Journal of Mechanical Science and Technology
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    • v.20 no.12
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    • pp.2218-2229
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    • 2006
  • A conservative finite-volume numerical method for unstructured grids with the cell-centered method has been developed for computing flow and heat transfer by combining the attractive features of the existing pressure-based procedures with the advances made in unstructured grid techniques. This method uses an integral form of governing equations for arbitrary convex polyhedra. Care is taken in the discretization and solution procedure to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. For both convective and diffusive fluxes the forms superior to both accuracy and stability are particularly adopted and formulated through a systematic study on the existing approximation ones. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are computed by using a linear reconstruction based on the divergence theorem. Momentum interpolation is used to prevent the pressure checkerboarding and a segregated solution strategy is adopted to minimize the storage requirements with the pressure-velocity coupling by the SIMPLE algorithm. An algebraic solver using iterative preconditioned conjugate gradient method is used for the solution of linearized equations. The flow analysis code (PowerCFD) developed by the present method is evaluated for its application to several 2-D structured-mesh benchmark problems using a variety of unstructured quadrilateral and triangular meshes. The present flow analysis code by using unstructured grids with the cell-centered method clearly demonstrate the same accuracy and robustness as that for a typical structured mesh.

MULTIGRID CONVERGENCE THEORY FOR FINITE ELEMENT/FINITE VOLUME METHOD FOR ELLIPTIC PROBLEMS:A SURVEY

  • Kwak, Do-Y.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.12 no.2
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    • pp.69-79
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    • 2008
  • Multigrid methods finite element/finite volume methods and their convergence properties are reviewed in a general setting. Some early theoretical results in simple finite element methods in variational setting method are given and extension to nonnested-noninherited forms are presented. Finally, the parallel theory for nonconforming element[13] and for cell centered finite difference methods [15, 23] are discussed.

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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.

MULTIGRID METHOD FOR TOTAL VARIATION IMAGE DENOISING

  • HAN, MUN S.;LEE, JUN S.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.6 no.2
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    • pp.9-24
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    • 2002
  • Total Variation(TV) regularization method is effective for reconstructing "blocky", discontinuous images from contaminated image with noise. But TV is represented by highly nonlinear integro-differential equation that is hard to solve. There have been much effort to obtain stable and fast methods. C. Vogel introduced "the Fixed Point Lagged Diffusivity Iteration", which solves the nonlinear equation by linearizing. In this paper, we apply multigrid(MG) method for cell centered finite difference (CCFD) to solve system arise at each step of this fixed point iteration. In numerical simulation, we test various images varying noises and regularization parameter $\alpha$ and smoothness $\beta$ which appear in TV method. Numerical tests show that the parameter ${\beta}$ does not affect the solution if it is sufficiently small. We compute optimal $\alpha$ that minimizes the error with respect to $L^2$ norm and $H^1$ norm and compare reconstructed images.

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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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    • 2003.08a
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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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Efficient 3D Acoustic Wave Propagation Modeling using a Cell-based Finite Difference Method (셀 기반 유한 차분법을 이용한 효율적인 3차원 음향파 파동 전파 모델링)

  • Park, Byeonggyeong;Ha, Wansoo
    • Geophysics and Geophysical Exploration
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    • v.22 no.2
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    • pp.56-61
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    • 2019
  • In this paper, we studied efficient modeling strategies when we simulate the 3D time-domain acoustic wave propagation using a cell-based finite difference method which can handle the variations of both P-wave velocity and density. The standard finite difference method assigns physical properties such as velocities of elastic waves and density to grid points; on the other hand, the cell-based finite difference method assigns physical properties to cells between grid points. The cell-based finite difference method uses average physical properties of adjacent cells to calculate the finite difference equation centered at a grid point. This feature increases the computational cost of the cell-based finite difference method compared to the standard finite different method. In this study, we used additional memory to mitigate the computational overburden and thus reduced the calculation time by more than 30 %. Furthermore, we were able to enhance the performance of the modeling on several media with limited density variations by using the cell-based and standard finite difference methods together.

A UNIFIED STABILIZED FINITE VOLUME METHOD FOR STOKES AND DARCY EQUATIONS

  • Boukabache, Akram;Kechkar, Nasserdine
    • Journal of the Korean Mathematical Society
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    • v.56 no.4
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    • pp.1083-1112
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    • 2019
  • In this paper, we present and analyze a cell-centered collocated finite volume scheme for incompressible flows to compute solutions simultaneous to Stokes and Darcy equations by applying a pressure jump stabilization term to avoid locking. We prove that the new stabilized FV formulation satisfies a discrete inf-sup condition and error estimates for both problems. Finally, we present some numerical examples confirming this analysis.