• Title/Summary/Keyword: structured mesh

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정렬 및 비정렬 격자를 이용한 선박 저항 계산에서 Courant 수의 공간 분포 및 LTS 기법의 효율성에 관한 연구 (A Study on Spatial Distributions of Courant Number and Numerical Efficiency of LTS Method in Calculation of Ship Resistance Using Structured and Unstructured Meshes)

  • 이상봉;백광준;박동우
    • 대한조선학회논문집
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    • 제54권2호
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    • pp.83-89
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    • 2017
  • Numerical simulations of ship resistance have been performed to compare spatial characteristics of Courant number when using structured and unstructured meshes. When Euler scheme was used for time integration, the structured mesh provided a more efficient calculation because the calculation time interval was larger than that of unstructured mesh. The automatic generation of very small meshes in the unstructured mesh was mainly responsible for the limitation of calculation time interval. When local time stepping Euler scheme was applied, however, the ship resistance of unstructured mesh showed a rapid convergence while a slow convergence of ship resistance in structured mesh was caused by the small time interval in bulbous bow.

3차원 얼굴 복원을 위한 구조 광 영상에서의 2차원 메쉬 추출 (Extracting 2D-Mesh from Structured Light Image for Reconstructing 3D Faces)

  • 이득용;오일석
    • 한국콘텐츠학회:학술대회논문집
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    • 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
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    • pp.248-251
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    • 2007
  • 본 논문은 3차원 얼굴 영상을 복원하기 위해 구조 광(structured light) 영상에서 2차원 메쉬를 추정하는 방법을 제안한다. 프로젝터를 사용하여 얼굴에 구조 광을 투영하고 카메라로 찍어 구조 광 영상을 획득한다. 획득한 영상에서 투영된 격자점을 추출한다. 격자점들의 위치와 각도를 사용하여 2차원 메쉬를 추출한다. 추출 과정에서 발생한 오류를 편집하고 정확한 2차원 메쉬를 추출한다.

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Numerical Simulation of Wind Pressures on a High-rise Building by Auto-mesh System

  • Tang, Yuanzhe;Cao, Shuyang
    • 국제초고층학회논문집
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    • 제8권4호
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    • pp.255-264
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    • 2019
  • This paper describes large eddy simulation of wind pressures on a square cylinder in a uniform flow and a high-rise building immersed in an atmospheric turbulent boundary layer. For the atmospheric boundary layer case, the inflow turbulence is generated by a numerical wind tunnel. In the numerical simulation, particular attention is devoted to the performance of an auto hexahedral non-structural mesh. Both simulations are performed for three grid systems: an auto hexahedral non-structured grid, a structured Cartesian grid and a non-structured triangular prism grid, and for three grid numbers. The present study shows that the auto hexahedral unstructured mesh achieves the best simulation results for wind pressures on the square cylinder and the high-rise building. When the grid number is sufficiently large, the differences among the results obtained from the three investigated grid systems are not significant. However, the advantage of the auto hexahedral unstructured mesh becomes clear when the grid number decreases, because it enables a balanced distribution of orthogonal grids. The results described in this paper demonstrate that the auto hexahedral non-structured mesh has good potential applicability to simulation of urban flows.

비정형격자 압력기준 유동해석기법을 이용한 비압축성 유동해석 (Unstructured-grid Pressure-based Method for Analysing Incompressible flows)

  • 김종태;김태준;김용모
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 1998년도 추계 학술대회논문집
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    • pp.42-47
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    • 1998
  • The pressure-based methods are very popular in CFD because it requires less computer core memory compared to other coupled or density-based solvers. Currently structured-mesh methodology based on pressure-based algorithm is quite mature to apply to the practical problems. The unstructured mesh method needs much more computer memory than the structured-mesh method. However the pressure-based method utilizing the sequential approach does not require very large memory used for unstructured-mesh density-based solvers. The present study has developed the unstructured grid pressure-based method. Cell-centered finite volume method was selected due to robustness for imposing various boundary conditions and easy implementation of higher-order upwind scheme. The predictive capability of present method has validated against several benchmark problems.

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OpenFOAM과 어댑티드 격자를 이용한 난류 경계층의 직접 수치 모사 (Direct Numerical Simulations of Turbulent Boundary Layer using OpenFOAM and Adapted Mesh)

  • 이상봉
    • 대한조선학회논문집
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    • 제53권3호
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    • pp.210-216
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    • 2016
  • Direct numerical simulations of a spatially developing turbulent boundary layer on a flat plate have been performed to verify the applicability of OpenFOAM and adapted mesh with prism layers to turbulent numerical simulation with high fidelity as well as provide a guideline on numerical schemes and parameters of OpenFOAM. Reynolds number based on a momentum thickness at inlet and a free-stream velocity was Reθ=300. Time dependent inflow fields with near-wall turbulent structures were generated by a method of Lund et al. (1998), which was to extract instantaneous velocity fields from an auxiliary simulation with rescaled and recycled velocities at inlet. To ascertain the statistical characteristics of turbulent boundary layer, the mean profiles of streamwise velocity and turbulent intensities obtained from structured and adapted meshes were compared with the previous data.

웹 환경에서의 입체적 가시화를 위한 3-D 가상현실 기법의 적용 (STUDY ON 3-D VIRTUAL REALITY FOR STEREOSCOPIC VISUALIZATION ON THE WEB)

  • 이장훈;박인철;김정훈;김병수
    • 한국전산유체공학회지
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    • 제16권1호
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    • pp.30-35
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    • 2011
  • In this paper, our effort to apply 3-D Virtual Reality system for stereoscopic visualization of mesh data on the web is briefly described. This study is an extension of our previous and on-going research efforts to develop an automatic grid generation program specialized for wing mesh, named as eGWing. The program is developed by using JAVA programming language, and it can be used either as an application program on a local computer or as an applet in the network environment. In this research advancing layer method(ALM) augmented by elliptic smoothing method is used for the structured grid generation. And to achieve a stereoscopic viewing capability, two graphic windows are used to render its own viewing image for the left and right eye respectively. These two windows are merged into one image using 3D monitor and the viewers can see the mesh data visualization results with stereoscopic depth effects by using polarizing glasses. In this paper three dimensional mesh data visualization with stereoscopic technique combined with 3D monitor is demonstrated, and the current achievement would be a good start-up for further development of low-cost high-quality stereoscopic mesh data visualization system which can be shared by many users through the web.

Hybrid mesh 및 sliding mesh를 이용한 선박 저항추진 성능 시험 (SHIP RESISTANCE AND PROPULSION PERFORMANCE TEST USING HYBRID MESH AND SLIDING MESH)

  • 박범진;이신형
    • 한국전산유체공학회:학술대회논문집
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    • 한국전산유체공학회 2009년 추계학술대회논문집
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    • pp.77-83
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    • 2009
  • In this study, we conducted resistance and propulsion performance test of ship composed of the Resistance Test, Propeller Open Water Test and Self Propulsion Test using the CFD(Computational Fluid Dynamics). We used commercial RANS(Reynolds Averaged Navier Stokes equation) solver, as a calculating tool. The unstructured grids were used in a bow and stern of ship, having complex shape, for a convenience of generating grids, and the structured grids were adopted in a central hull and rest of hull having a relatively simple shape which is called hybrid grid method. In addition, The sliding mesh method was adopted to rotate a propeller directly in the Propeller Open Water and Self Propulsion Test. The Resistance Test and Self Propulsion Test were calculated using Volume of Fluid (VOF) model and considering a free surface. And all The three cases were applied realizable k-epsilon model as the turbulence model. The results of calculations were verified for the suitability of calculations by comparing MOERI's EFD results.

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마이크로 채널을 이용한 탄화수소 연료개질에 관한 연구 (Study on hydrocarbon reforming using microchannel catalysts)

  • 배규종;박준근;배중면
    • 한국신재생에너지학회:학술대회논문집
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    • 한국신재생에너지학회 2007년도 춘계학술대회
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    • pp.33-36
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    • 2007
  • Currently, many structured catalysts using microchannel are researched to apply to fuel reforming. In this paper, ceramic monolith and metal mesh as structured catalysts are investigated for catalytic autothermal reforming. When GHSV increases, each structured catalyst has better performances(hydrogen production, fuel conversion) than packed bed catalyst for autothermal reforming. The major causes seem to be the elevated heat and mass transfer, gas phase reaction and redistribution of packed bed due to high pressure drop.

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