• Title/Summary/Keyword: Cartesian cut cell

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NUMERICAL METHOD FOR MOLTEN METAL FLOW SIMULATION WITH CUT CELL (Cut Cell을 고려하는 주조유동 해석 방법)

  • Choi, Y.S.;Hong, J.H.;Hwang, H.Y.
    • 한국전산유체공학회:학술대회논문집
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    • 2011.05a
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    • pp.518-522
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    • 2011
  • Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. A cut cell method on Cartesian grids has been developed to simulate three-dimensional mold filling Cut cells at a cast-mold interface are generated on Cartesian grids. Governing equations were computed using volume and areas of cast at cut cells. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the patial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. We can know the momentum energy at the cut cell is conserved by using the cut cell method. By using the cut cell method. performance of computation gets better because of reducing the whole number of meshes.

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Numerical Simulation of Dam-Break Problem with Cut-cell Method (분할격자를 이용한 댐붕괴파의 수치해석)

  • Kim, Hyung-Jun;Yoo, Je-Seon;Lee, Seung-Oh;Cho, Yong-Sik
    • Proceedings of the Korea Water Resources Association Conference
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    • 2008.05a
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    • pp.1752-1756
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    • 2008
  • A simple, accurate and efficient mesh generation technique, the cut-cell method, is able to represent an arbitrarily complex geometry. Both structured and unstructured grid meshes are used in this method. First, the numerical domain is constructed with regular Cartesian grids as a background grid and then the solid boundaries or bodies are cut out of the background Cartesian grids. As a result, some boundary cells can be contained two numerical conditions such as the flow and solid conditions, where the special treatment is needed to simulate such physical characteristics. The HLLC approximate Riemann solver, a Godunov-type finite volume method, is employed to discretize the advection terms in the governing equations. Also, the TVD-WAF method is applied on the Cartesian cut-cell grids to stabilize numerical results. Present method is validated for the rectangular dam break problems. Initially, a conventional grid is constructed with the Cartesian regular mesh only and then applied to the dam-break flow simulation. As a comparative simulation, a cut-cell grids are applied to represent the flow domain rotated with arbitrary angles. Numerical results from this study are compared with the results from the case of the Cartesian regular mesh only. A good agreement is achieved with other numerical results presented in the literature.

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Development of a Numerical Model of Shallow-Water Flow using Cut-cell System (분할격자체계를 이용한 천수흐름 수치모형의 개발)

  • Kim, Hyung-Jun;Lee, Seung-Oh;Cho, Yong-Sik
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.4
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    • pp.91-100
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    • 2008
  • Numerical implementation with a Cartesian cut-cell method is conducted in this study. A Cartesian cut-cell method is an easy and efficient mesh generation methodology for complex geometries. In this method, a background Cartesian grid is employed for most of computational domain and a cut-cell grid is applied for the peculiar grids where the flow characteristics are changed such as solid boundary to enhance the accuracy, applicability and efficiency. Accurate representation of complex geometries can be obtained by using the cut-cell method. The cut-cell grids are constructed with irregular meshes which have various shape and size. Therefore, the finite volume method is applied to numerical discretization on a irregular domain. The HLLC approximate Riemann solver, a Godunov-type finite volume method, is employed to discretize the advection terms in the governing equations. The weighted average flux method applied on the Cartesian cut cell grid for stabilization of the numerical results. To validate the numerical model using the Cartesian cut-cell grids, the model is applied to the rectangular tank problem of which the exact solutions exist. As a comparison of numerical results with the analytical solutions, the numerical scheme well represents flow characteristics such as free surface elevation and velocities in x-and y-directions in a rectangular tank with the Cartesian and cut-cell grids.

Numerical Method for Improving the Accuracy of Molten Metal Flow (주조유동의 정확도 개선을 위한 수치기법 연구)

  • Choi, Young-Sim;Hong, Jun-Ho;Hwang, Ho-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.253-258
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    • 2012
  • The Cartesian grid system has generally been used in casting simulations, even though it does not represent sloped and curved surfaces very well. These distorted boundaries cause several problems, and special treatment is necessary to resolve them. A cut cell method on a Cartesian grid has been developed for the simulation of threedimensional mold filling. Cut cells at a cast/mold interface are generated on Cartesian grids, and the governing equations are computed using the volume and areas of the cast at the cut cells. In this paper, we propose a new method based on the partial cell treatment (PCT) that can consider the cutting cells which are cut by the cast and the mold. This method provides a better representation of the surface geometry, and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process are computed and validated.

Mold Filling Simulation with Cut Cell in the Cartesian Grid System (직교 격자 계에서 주조 유동 시뮬레이션의 정확한 해석 방법)

  • Choi, Young-Sim;Nam, Jeong-Ho;Hong, Jun-Ho;Hwang, Ho-Young
    • Journal of Korea Foundry Society
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    • v.29 no.1
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    • pp.33-37
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    • 2009
  • Cartesian grid system has mainly been used in the casting simulation even though it does not nicely represent sloped and curved surfaces. These distorted boundaries cause several problems. A special treatment is necessary to clear these problems. In this paper, we propose a new method that can consider the cutting cells which are cut by casting and mold based on the partial cell treatment (PCT). This method provides a better representation of geometry surface and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian grid system. Various test examples for several casting process were computed and validated. The analysis results of more accurate fluid flow pattern and less momentum loss owing to the stepped boundaries in the Cartesian grid system were confirmed. By using the cut cell method, performance of computation gets better because of reducing the whole number of meshes.

DEVELOPMENT OF A 2-D UNSTEADY FLOW SIMULATION CODE USING CARTESIAN MESHES (직교격자를 이용한 2차원 비정상 유동해석 코드 개발)

  • Jung, Min-Kyu;Lee, Jae-Eun;Park, Se-Youn;Kwon, Oh-Joon;Kwon, Jang-Hyuk;Shin, Ha-Yong
    • 한국전산유체공학회:학술대회논문집
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    • 2009.04a
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    • pp.116-120
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    • 2009
  • A two-dimensional unsteady inviscid flow solver has been developed for the simulation of complex geometric configurations on adaptive Cartesian meshes. Embedded condition was used for boundary condition and a predictor-corrector explicit time marching scheme was used for time-accurate numerical simulation. The Cartesian mesh generator, which was previously developed for steady problem, was used grid generation for unsteady flow. The solver was based on ALE formulation for body motion. For diminishing the effects of cut-cells, the cell merging method was used. Using cell merging method, it was eliminated the CFL constraints. The conservation problem, which is caused cell-type variation around region swept by solid boundary, was also solved using cell merging method. The results are presented for 2D circular cylinder and missile launching problem.

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Study on the Application of Casting Flow Simulation with Cut Cell Method by the Casting process (Cut Cell 방법을 활용한 공정별 주조유동해석 적용 연구)

  • Young-Sim Choi
    • Journal of Korea Foundry Society
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    • v.43 no.6
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    • pp.302-309
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    • 2023
  • In general, castings often have complex shapes and significant variations in thickness within a single product, making grid generation for simulations challenging. Casting flows involve multiphase flows, requiring the tracking of the boundary between air and molten metal. Additionally, considerable time is spent calculating pressure fields due to density differences in a numerical analysis. For these reasons, the Cartesian grid system has traditionally been used in mold filling simulations. However, orthogonal grids fail to represent shapes accurately, leading to a momentum loss caused by the stair-like grid patterns on curved and sloped surfaces. This can alter the flow of molten metals and result in incorrect casting process designs. To address this issue, simulations in the Cartesian grid system involve creating a large number of grids to represent shapes more accurately. Alternatively, the Cut Cell method can be applied to address the problems arising from the Cartesian grid system. In this study, analysis results based on the number of grid in the Cartesian grid system for a casting flow analysis were compared with results obtained using the Cut Cell method. Casting flow simulations of actual products during various casting processes were also conducted, and these results were analyzed with and without applying the Cut Cell method.

The Application of Cartesian Cut Cell Method for a High-Voltage GCB (분할격자법을 이용한 초고압 가스차단기 유동해석)

  • Lee Jong C.;Ahn Heui-Sub;Kim Youn J.
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.91-94
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    • 2002
  • It is important to develop new effective technologies for increasing the interruption capacity and reducing the size of a GCB (Gas Circuit Breaker). It is not easy to test the real GCB model in practice as in theory. Therefore, a simulation tool based on a CFD (Computational Fluid Dynamics) algorithm has been developed to facilitate an optimization of the interrupter. But the choice of grid is not at all trivial in the complicated geometries like a GCB. In this paper, we have applied a CFD-CAD integration using Cartesian cut-cell method, which is one of the grid generation techniques for dealing with complex and multi-component geometries.

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Octree Generation and Clipping Algorithm using Section Curves for Three Dimensional Cartesian Grid Generation (삼차원 직교 격자 생성을 위한 단면 커브를 이용한 옥트리 생성과 셀 절단 알고리듬)

  • Kim, Dong-Hun;Shin, Ha-Yong;Park, Se-Youn;Yi, Il-Lang;Kwon, Jang-Hyuk;Kwon, Oh-Joon
    • Korean Journal of Computational Design and Engineering
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    • v.13 no.6
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    • pp.450-458
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    • 2008
  • Recently, Cartesian grid approach has been popular to generate grid meshes for complex geometries in CFD (Computational Fluid Dynamics) because it is based on the non-body-fitted technique. This paper presents a method of an octree generation and boundary cell clipping using section curves for fast octree generation and elimination of redundant intersections between boundary cells and triangles from 3D triangular mesh. The proposed octree generation method uses 2D Scan-Converting line algorithm, and the clipping is done by parameterization of vertices from section curves. Experimental results provide octree generation time as well as Cut-cell clipping time of several models. The result shows that the proposed octree generation is fast and has linear relationship between grid generation time and the number of cut-cells.

Development of Viscous Boundary Conditions in an Immersed Cartesian Grid Framework

  • Lee, Jae-Doo
    • Journal of Ship and Ocean Technology
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    • v.10 no.3
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    • pp.1-16
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    • 2006
  • Despite the high cost of memory and CPU time required to resolve the boundary layer, a viscous unstructured grid solver has many advantages over a structured grid solver such as the convenience in automated grid generation and vortex capturing by solution adaption. In present study, an unstructured Cartesian grid solver is developed on the basis of the existing Euler solver, NASCART-GT. Instead of cut-cell approach, immersed boundary approach is applied with ghost cell boundary condition, which can be easily applied to a moving grid solver. The standard $k-{\varepsilon}$ model by Launder and Spalding is employed for the turbulence modeling, and a new wall function approach is devised for the unstructured Cartesian grid solver. Developed approach is validated and the efficiency of the developed boundary condition is tested in 2-D flow field around a flat plate, NACA0012 airfoil, and axisymmetric hemispheroid.