• Title/Summary/Keyword: unstructured meshing

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Unstructured Tetrahedral Meshing by an Edge-Based Advancing Front Method

  • Kim, Young-Woong;Kwon, Gi-Whan;Chae, Soo-Won;Shim, Jae-Kyung
    • Journal of Mechanical Science and Technology
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    • v.16 no.2
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    • pp.211-218
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    • 2002
  • This paper proposes an unstructured tetrahedral meshing algorithm for CAD models in the IGES format. The work presented is based on the advancing front method, which was proposed by the third author. Originally, the advancing front method uses three basic operators, namely, trimming, wedging, and digging. In this research, in addition to the basic operators, three new operators splitting, local finishing, and octahedral-are added to stabilize the meshing process. In addition, improved check processes are applied to obtain better-shaped elements. The algorithm is demonstrated and evaluated by four examples.

The Influence of Meshing Strategies on the Propeller Simulation by CFD

  • Bahatmaka, Aldias;Kim, Dong-Joon
    • Journal of Advanced Research in Ocean Engineering
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    • v.4 no.2
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    • pp.78-85
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    • 2018
  • This paper presents a study of the effects of the free surface to marine propeller including the mesh effect of the models. In the present study, we conduct the numerical simulation for propeller performance employing the openwater test. The numerical simulations compare the meshing strategies for the propeller and show the effects on both thrust and torque. OpenFOAM is applied to solve the propeller problem and then open water performances of KCS propeller (KP505) are estimated using a Reynold-averaged Navier-Stokes equations (RANS) solver and the turbulence of the $K-{\omega}$ SST model. Unstructured meshes are used in the numerical simulation employing hexahedral meshing for mesh generation. The arbitrary mesh interfacing (AMI) and multiple rotating frame (MRF) are compared to define the best meshing strategy. The meshing strategies are evaluated through 3 classifications, i.e., coarse, medium, and fine mesh. Thus, the propeller can be performed utilizing the best mesh strategy. The computational results are validated by comparison with the experimental results. The $K_T$, $K_Q$, and efficiency of the propeller are compared to an experimental result and for all of the meshing strategies. Thus, the simulations show the influence of meshing in order to perform the propeller performances.

Quadrilateral Mesh Generation on Trimmed NURBS Surfaces

  • Chae, Soo-Won;Kwon, Ki-Youn
    • Journal of Mechanical Science and Technology
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    • v.15 no.5
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    • pp.592-601
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    • 2001
  • An automatic mesh generation scheme with unstructured quadrilateral elements on trimmed NURBS surfaces has been developed. In this paper NURBS surface geometries in the IGES format have been employed to represent geometric models. For unstructured mesh generation with quadrilateral elements, a domain decomposition algorithm employing loop operators has been modified. As for the surface meshing, an indirect 2D approach is proposed in which both quasi-expanded planes and projection planes are employed. Sampled meshes for complex models are presented to demonstrate the robustness of the algorithm.

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Automatic Tetrahedral Mesh Generation Using Advancing Front Technique with Node Searching (절점 탐색이 적용된 전진경계법에 의한 사면체 요소망의 자동생성)

  • 전성재;채수원
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.3
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    • pp.91-99
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    • 2004
  • An unstructured tetrahedral mesh generation algorithm has been presented. In order to construct better meshes in interior region by using an advancing front technique, a connecting operator and a local finishing operator II have been developed in addition to the existing operators. Before applying digging operators that generate new nodes inside of a meshing region, a connecting operator is employed that uses existing nodes which satisfy certain conditions for producing well-conditioned elements. The local finishing operator II is introduced to terminate the meshing process more flexibly on remaining subregions. With these new operators, tetrahedral meshing process becomes more robust and good quality of meshes are constructed.

Computation of Thermal Flow for Automotive Lamp by Using Geometric Octree Method (기하학적 Octree 격자생성법을 이용한 자동차 헤드램프 내부의 열유동 계산)

  • Sah Jong-Youb;Park Jong-Ryul;Kang Dong-Min
    • 한국전산유체공학회:학술대회논문집
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    • 2001.10a
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    • pp.152-156
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    • 2001
  • Three dimensional orthogonal grid generation is able to control effectively the grid spacing near the boundaries, but there are some difficulty to meshing complex geometry. The mesh complex geometry by orthogonal grid generation method must divide block of geometry It is required a careful skill, and long time. Its also difficulty to make unstructured mesh on complex geometry. Particularly, three dimensional geometry must have more time and effort. Recently, there have been growing interests in mesh generation of complex grometry, aslike an automobile headlamp, the heart. The method of easily meshing complex geometry is resarched to solve them. We suggest octree grid into one among these methods. As octrce grid is automaticaly adapted at the boundaries by determine the level operations to control the grid spacing near the boundaries are unnecessary. In this paper we showed throe dimensional mesh generation, and heat-flow analysis on the octree mesh.

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Automatic Tetrahedral Mesh Generation using Advancing Front Technique with Delaunay Node Searching (전진경계법에서 Delaunay 탐색조건을 이용한 사면체 요소망의 자동 생성)

  • 전성재;채수원
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1605-1608
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    • 2003
  • A unstructured tetrahedral mesh generation algorithm has been presented. To make better meshes in interior region using an advancing front technique, a connecting operator has been developed in addition to the existing operators. Before applying digging operators that generate new nodes inside of a meshing region, a connecting operator is employed that uses existing nodes which satisfy certain conditions for producing well-conditioned elements if possible. By introducing this new operator, tetrahedral meshing process becomes more robust and produces better quality of meshes.

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Flexible CFD meshing strategy for prediction of ship resistance and propulsion performance

  • Seo, Jeong-Hwa;Seol, Dong-Myung;Lee, Ju-Hyun;Rhee, Shin-Hyung
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.2 no.3
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    • pp.139-145
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    • 2010
  • In the present study, we conducted resistance test, propeller open water test and self-propulsion test for a ship's resistance and propulsion performance, using computational fluid dynamics techniques, where a Reynolds-averaged Navier-Stokes equations solver was employed. For convenience of mesh generation, unstructured meshes were used in the bow and stern region of a ship, where the hull shape is formed of delicate curved surfaces. On the other hand, structured meshes were generated for the middle part of the hull and the rest of the domain, i.e., the region of relatively simple geometry. To facilitate the rotating propeller for propeller open water test and self-propulsion test, a sliding mesh technique was adopted. Free-surface effects were included by employing the volume of fluid method for multi-phase flows. The computational results were validated by comparing with the existing experimental data.

Computation of Viscous Flows around a Two-dimensional Oscillating Airfoil ( Part 1. without Dynamic Stall ) (진동하는 2차원 날개 단면 주위에 대한 점성 유동장 계산( Part 1. 동적실속이 없는 경우 ))

  • Lee, Pyoung-Kuk;Kim, Hyoung-Tae
    • Journal of the Society of Naval Architects of Korea
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    • v.44 no.1 s.151
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    • pp.8-15
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    • 2007
  • In this paper, numerical calculations are performed to analyze the unsteady flow of NACA airfoil sections. In order to ease the flow computation for the fluid region changing in time, improve the quality of solution and simplify the grid generation for the oscillating foil flow, the computational method adopts a moving and deforming mesh with the multi-block grid topology. The multi-block, structured-unstructured hybrid grid is generated using the commercial meshing software Gridgen V15. The MDM (Moving & Deforming Mesh) and the UDF (User Define function) function of FLUENT 6 are adopted for computing turbulent flows of the foil in pitching motion. Computed unsteady lift and drag forces are compared with experimental data. in general, the characteristics of unsteady lift and drag of the experiments are reproduced well in the numerical analysis.