• Title/Summary/Keyword: 비 정렬격자

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An Unstructured 3-D Chimera Technique for Overlapped Bodies inRelative Motion (3차원 비정렬 중첩격자계를 이용한 서로 겹쳐진 물체들 간의 상대운동 해석기법에 관한 연구)

  • 안상준;권오준;정문승
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.8
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    • pp.1-7
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    • 2006
  • In the present study, A 3-D chimera technique for overlapped bodies in relative motion is studied using unstructured meshes. If all node points of a mesh element at solid boundary are in another body, this element is excluded from computational domain. For computation of unsteady flow, non-active cells have proper variables using interpolation and extrapolation. These variables are used in next time step. The motion of a launching trajectory ejected from a wing and the motion of deploying fins of a trajectory which have not been simulated are computed to conform practicality of this technique.

CONSERVATIVE OVERSET MESH TECHNIQUE ON 2-D UNSTRUCTURED MESHES (이차원 비정렬 격자계에서의 보존적 중첩 격자 기법)

  • Jung, M.S.;Kwon, O.J.;Kang, H.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03a
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    • pp.27-32
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    • 2008
  • In the present study, a conservative overset mesh technique has been developed on 2-D unstructured meshes. A new domain connection technique between independent mesh blocks was proposed to satisfy the conservation of mass, momentum, or energy in entire computational domain. The present technique was applied to several classical computational problems to validate the superiority of the conservative method to the non-conservative method.

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CONSERVATIVE OVERSET MESH TECHNIQUE ON 2-D UNSTRUCTURED MESHES (이차원 비정렬 격자계에서의 보존적 중첩 격자 기법)

  • Jung, M.S.;Kwon, O.J.;Kang, H.J.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.10a
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    • pp.27-32
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    • 2008
  • In the present study, a conservative overset mesh technique has been developed on 2-D unstructured meshes. A new domain connection technique between independent mesh blocks was proposed to satisfy the conservation of mass, momentum, or energy in entire computational domain. The present technique was applied to several classical computational problems to validate the superiority of the conservative method to the non-conservative method.

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Inverse Radiation Analysis of a Two-Dimensional Irregular Geometry Using Unstructured Triangular Meshes (비정렬 삼각 격자를 이용한 2 차원 비직교 형상에서의 역복사 해석)

  • Yi, Kyung-Joo;Baek, Seung-Wook;Kim, Man-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.6
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    • pp.561-567
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    • 2011
  • The inverse radiation analysis of a two-dimensional irregular configuration using unstructured triangular meshes is presented. In this study, an enclosure filled with an absorbing, emitting and scattering medium with diffusely emitting and reflecting opaque boundaries is considered. The finite volume method is applied to solve the radiative transfer equation in order to simulate the measured incident radiation values which are used as input data for the inverse analysis. The conjugate gradient method is adopted for the estimation of wall emissivities by minimizing the objective function at each iteration step. To verify the performance of the unstructured grid system, we compare the results with those using a structured grid system for the two-dimensional lopsided shape. The effect of measurement errors on the estimation accuracy is also investigated.

Prediction of Aeroelastic Displacement Under Close BVI Using Unstructured Dynamic Meshes (비정렬 동적격자를 이용한 블레이드-와류 간섭에 따른 공탄성 변위예측)

  • Jo, Kyu-Won;Oh, Woo-Sup;Kwon, Oh-Joon;Lee, In
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.37-45
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    • 2002
  • A two-dimensional unsteady, inviscid flow solver has been developed for the simulation of airfoil-vortex interactions on unstructured dynamically adapted meshes. The Euler solver is based on a second-order accurate implicit time integration using a point Gauss-Seidel relaxation scheme and a dual time-step subiteration. A vertex-centered, finite-volume discretization is used in conjunction with the Roe's flux-difference splitting. An unsteady solution-adaptive dynamic mesh scheme is used by adding and deleting mesh points to take account of both spatial and temporal variations of the flow field. The effect of vortex interaction on the aeroelastic displacement of an airfoil attached to the idealized two degree-of-freedom spring system is investigated.

Convergence and Stability Analysis of LU Scheme on Unstructured Meshes: Part I - Euler Equations (비정렬 격자계에서 LU Implicit Scheme의 수렴성 및 안정성 해석 : Part I-오일러 방정식)

  • Kim, Joo-Sung;Kwon, Oh-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.9
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    • pp.1-11
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    • 2004
  • A comprehensive study has been made for the investigation of the convergence and stability characteristics of the LU scheme for solving the Euler equations on unstructured meshes. The von Neumann stability analysis technique was initially applied to a scalar model equation, and then the analysis was extended to the Euler equations. The results indicated that the convergence rate is governed by a specific combination of flow parameters. Based on this insight, it was shown that the LU scheme does not suffer any convergence deterioration at all grid aspect ratios, as long as the local time step is defined using an appropriate parameter combination.

Numerical Simulation of Surface Tension-Dominant Multiphase Flows by Using Volume-Capturing Method and Unstructured Grid System (비정렬격자계와 체적포착법을 사용한 표면장력이 지배적인 다상유동 수치해석)

  • Myong, Hyon-Kook
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.7
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    • pp.723-733
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    • 2011
  • A numerical method of the CSF(Continuum Surface Force) model is presented for the calculation of the surface tension force and implemented in an in-house solution code(PowerCFD). The present method(code) employs an unstructured cell-centered method based on a conservative pressure-based finite-volume method with volume capturing method(CICSAM) in a volume of fluid(VOF) scheme for phase interface capturing. The application of the present method to a 2-D liquid drop problem is illustrated by an equilibrium and nonequilibrium oscillating drop calculation. It is found that the present method simulates efficiently and accurately surface tension-dominant multiphase flows.

Convergence and Stability Analysis of LU Scheme on Unstructured Meshes: Part II - Navier-Stokes Equations (비정렬 격자계에서 LU implicit scheme의 수렴성 및 안정성 해석: Part II - Navier-Stokes 방정식)

  • Kim, Joo-Sung;Kwon, Oh-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.32 no.8
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    • pp.1-11
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    • 2004
  • A comprehensive study has been made for the investigation of the convergence and stability characteristics of the LU scheme for solving the Navier-Stokes equations on unstructured meshes. For this purpose the characteristics of the LU scheme was initially studied for a scalar model equation. Then the analysis was extended to the Navier-Stokes equations. It was shown that the LU scheme has an inherent stiffness in the streamwise direction. This stiffness increases when the grid aspect ratio becomes high and the cell Reynolds number becomes small. It was also shown that the stiffness related to the grid aspect ratio can be effectively eliminated by performing proper subiteration. The results were validated for a flat-plate turbulent flow.

Development of a 3-D Viscous Flow Solver Based on Unstructured Hybrid Meshes (비정렬 혼합 격자계 기반의 삼차원 점성 유동해석코드 개발)

  • Jung, Mun-Seung;Kwon, Oh-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.8
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    • pp.677-684
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    • 2007
  • In the Present Study, a 3-D viscous flow solver, based on unstructured hybrid meshses containing tetrahedra, prisms and pyramids, has been developed. A finite-volume discretization scheme is used for solving the compressible Navier-Stokes equations. A cell-vertex median dual volume is used for spatial discretization. The one-equation Spalart-Allmaras turbulence model has been adopted to evaluate the eddy viscosity. Validation were made by computing laminar and turbulent flows around a 3-D wing for steady flows and turbulent flows around an oscillating 3-D wing in harmonic motion for unsteady flows.

Development of an Unstructured Parallel Overset Mesh Technique for Unsteady Flow Simulations around bodies with Relative Motion (상대운동이 있는 물체주위의 비정상 유동해석을 위한 병렬화된 비정렬 중첩격자기법 개발)

  • Jung, Mun-Seung;Kwon, Oh-Joon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.2
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    • pp.1-10
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    • 2005
  • An unstructured parallel overset mesh method has been developed for the simulation of unsteady flows around multiple bodies in relative motion. For this purpose, an efficient and robust search method is proposed for the unstructured grid system. A new data-structure is also proposed to handle the variable number of data on parallel sub-domain boundary. The interpolation boundary is defined for data communication between grid systems. An interpolation method to retain second-order spatial accuracy and to treat the points inside the neighboring solid bodies are also suggested. A single store separating from the Eglin/Pylon configuration is calculated and the result is compared with experimental data for validation. Simulation of unsteady flows around multiple bodies in relative motion is also performed.