• Title, Summary, Keyword: Solution-adaptive mesh refinement

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Application of CIP Method on Advection Equation by Adaptive Mesh Refinement (AMR-CIP법을 이용한 이류 방정식에 관한 수치해석)

  • Yoon, Seong-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.7
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    • pp.871-878
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    • 2004
  • An accurate adaptive mesh refinement based on the CIP method is proposed and it is applied to solve the two dimensional advection equations. In this method, the level set function is employed to refine and merge the computation cells. To enhance the accuracy of the solution, the spatial discretization is made by the CIP method. The CIP method has many advantages such as the third order accuracy, less diffusivity, and shape conserving. The mathematical formulation and numerical results are also described. To verify the efficiency, accuracy, and capability of the proposed algorithim, two dimensional rotating slotted cylinder and idealized frontogenesis are numerically simulated by the present scheme. As results, it is confirmed that the present method gives an efficient, reasonable solution in the advection equation.

An Unstructured Mesh Technique for Rotor Aerodynamics

  • Kwon, Oh-Joon
    • 한국전산유체공학회:학술대회논문집
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    • pp.24-25
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    • 2006
  • An unstructured mesh method has been developed for the simulation of steady and time-accurate flows around helicopter rotors. A dynamic and quasi-unsteady solution-adaptive mesh refinement technique was adopted for the enhancement of the solution accuracy in the local region of interest involving highly vortical flows. Applications were made to the 2-D blade-vortex interaction aerodynamics and the 3-D rotor blades in hover. The interaction between the rotor and the airframe in forward flight was investigated by introducing an overset mesh technique.

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2-D Magnetostatic Field Analysis Using Adaptive Boundary Element Method (적응 경계요소법을 이용한 2차원 정자장 해석)

  • Koh, Chang-Seop;Jeon, Ki-Eock;Hahn, Song-Yop;Jung, Hyun-Kyo
    • Proceedings of the KIEE Conference
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    • pp.23-27
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    • 1990
  • Adaptive mesh refinement scheme is incorporated with the Boundary Element Method (BEM) in order to get accurate solution with relatively fewer unknowns for the case of magnetostatic field analysis and A new and simple posteriori local error estimation method is presented. The local error is defined as integration over the element of the difference between solutions acquired us ing second order and first order interpolation function and is used as the criterion for mesh refinement at given grid. Case study for two dimensional problems with singular point reveals that meshes are concentrated on the neighbor of singular point and the error is decreased gradually and the solutions calculated on the domain are converged to the analytic solution as the number of unknowns increases. The adaptive mesh gives much better rate of convergence in global errors than the uniform mesh.

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DEVELOPMENT OF HIGH-ORDER ADAPTIVE DISCONTINUOUS GALERKIN METHOD FOR UNSTEADY FLOW SIMULATION (비정상 유동 해석을 위한 고차정확도 격자 적응 불연속 갤러킨 기법 개발)

  • Lee, H.D.;Choi, J.H.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.534-541
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    • 2010
  • A high-order accurate Euler flow solver based on a discontinuous Galerkin method has been developed for the numerical simulation of unsteady flows on unstructured meshes. A multi-level solution-adaptive mesh refinement/coarsening technique was adopted to enhance the resolution of numerical solutions efficiently by increasing mesh density in the high-gradient region. An acoustic wave scattering problem was investigated to assess the accuracy of the present discontinuous Galerkin solver, and a supersonic flow in a wind tunnel with a forward facing step was simulated by using the adaptive mesh refinement technique. It was shown that the present discontinuous Galerkin flow solver can capture unsteady flows including the propagation and scattering of the acoustic waves as well as the strong shock waves.

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Adaptive finite element wind analysis with mesh refinement and recovery

  • Choi, Chang-Koon;Yu, Won-Jin
    • Wind and Structures
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    • v.1 no.1
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    • pp.111-125
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    • 1998
  • This paper deals with the development of variable-node element and its application to the adaptive h-version mesh refinement-recovery for the incompressible viscous flow analysis. The element which has variable mid-side nodes can be used in generating the transition zone between the refined and unrefined element and efficiently used for the construction of a refined mesh without generating distorted elements. A modified Guassian quadrature is needed to evaluate the element matrices due to the discontinuity of derivatives of the shape functions used for the element. The penalty function method which can reduce the number of the independent variables is adopted for the purpose of computational efficiency and the selective reduced integration is carried out for the convection and pressure terms to preserve the stability of solution. For the economical analysis of transient problems in which the locations to be refined are changed in accordance with the dynamic distribution of velocity gradient, not only the mesh refinement but also the mesh recovery is needed. The numerical examples show that the optimal mesh for the finite element analysis of a wind around the structures can be obtained automatically by the proposed scheme.

Adaptive finite element wind analysis with mesh refinement and recovery (요소 세분화 및 재결합을 이용한 바람의 적응적 유한요소 해석)

  • 최창근;유원진;이은진
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.60-67
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    • 1998
  • This paper deals with the development of a variable-node element and its application to the adaptive h-version mesh refinement-recovery for the incompressible viscous flow analysis. The element which has variable mid-side nodes can be used in generating the transition zone between the refined and unrefined elements and efficiently used for construction of a refined mesh without generating distorted elements. A modified Gaussian quadrature is needed to evaluate the element matrices due to the discontinuity of derivatives of the shape functions used for the element. The penalty function method which can reduce the number of independent variables is adopted for the purpose of computational efficiency and the selective reduced integration is carried out for the convection and pressure terms to preserve the stability of solution. For the economical analysis of transient problems, not only the mesh refinement but also the mesh recovery is needed. The numerical examples show that the optimal mesh for the finite element analysis of a wind around the structures can be obtained automatically by the proposed scheme.

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Ultimate response of bionics shells

  • Tesar, Alexander;Minar, Michal
    • Structural Engineering and Mechanics
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    • v.14 no.2
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    • pp.135-150
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    • 2002
  • Numerical analysis of ultimate behaviour of thin bionics shells is treated in present paper. Interactive conditions in resonance and stability ultimate response are considered. Numerical treatment of nonlinear problems appearing is made using the updated Lagrangian formulation of motion. Each step of the iteration approaches the solution of linear problem and the feasibility of parallel processing FETM-technique with adaptive mesh refinement and substructuring for the analysis of ultimate action of thin bionics shells is established. Some numerical results are submitted in order to demonstrate the efficiency of the procedures suggested.

Numerical Comparisons Between URANS and Hybrid RANS/LES at a High Reynolds Number Flow Using Unstructured Meshes

  • You, Ju-Yeol;Kwon, Oh-Joon
    • International Journal of Aeronautical and Space Sciences
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    • v.11 no.1
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    • pp.41-48
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    • 2010
  • In the present study, the turbulent flow fields around a circular cylinder at $Re=3.6{\times}10^6$ were investigated based on an unstructured mesh technique, and the comparisons between URANS(S-A, SST) and hybrid RANS/LES(DES, SAS) methods for the simulation of high Reynolds number flow have been conducted. For this purpose, unsteady characteristics of vortex shedding and time-averaged quantities were compared. A quasi-steady solution-adaptive mesh refinement was also made for the URANS and hybrid RANS/LES approaches. The results showed that the simple changes in the turbulent length scale or source term of turbulent models made the flow fields less dissipative and more realistic in hybrid RANS/LES methods than the URANS approaches.

2-D Magnetostatic Field Analysis Using Adaptive Boundary Element Method (적응 경계요소법을 이용한 2형원 정자계 해석)

  • 고창섭;정현교;한송엽
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.40 no.3
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    • pp.243-249
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    • 1991
  • Adaptive mesh refinement scheme is incorporated with the boundary element analysis in order to get accurate solution with relatively fewer unnowns for magnetostatic field analysis. A new andsimple posteriori local error estimate is also presented. The local error is defined as an integraktion over the element of the difference between solutions from quadratic interpolation functions and linear interpolation functions and is used as the criterion for mesh refinement. Case study with a singular point reveals that adaptive meshes are more efficient in accuracy of solutions than uniform meshs generated by dividing al the elements evenly. The adaptive meshes give much better rate of convergence in global errors than the uniform meshes.

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Development of a 2-dimensional Flow Solver using Hybrid Unstructured and Adaptive Cartesian Meshes (비정렬 및 적응 직교격자를 이용한 2차원 혼합격자계 유동해석 코드 개발)

  • Jung, M.K.;Kwon, O.J.
    • 한국전산유체공학회:학술대회논문집
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    • pp.294-301
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    • 2011
  • A two-dimensional hybrid flaw solver has been developed for the accurate and efficient simulation of steady and unsteady flaw fields. The flow solver was cast to accommodate two different topologies of computational meshes. Triangular meshes are adopted in the near-body region such that complex geometric configurations can be easily modeled, while adaptive Cartesian meshes are, utilized in the off-body region to resolve the flaw more accurately with less numerical dissipation by adopting a spatially high-order accurate scheme and solution-adaptive mesh refinement technique. A chimera mesh technique has been employed to link the two flow regimes adopting each mesh topology. Validations were made for the unsteady inviscid vol1ex convection am the unsteady turbulent flaws over an NACA0012 airfoil, and the results were compared with experimental and other computational results.

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