• 한국전산유체공학회지
• /
• 제12권3호
• /
• pp.20-28
• /
• 2007

A fast and robust method of grid generation to multiple functions has been developed for flow analysis in three dimensional space. It is based on the Non-Uniform Rational B-Spline(NURBS) of an approximation method. Many of NURBS intrinsic properties are introduced and much more easily understood. The grid generation method, details of numerical implementation. examples of application, and potential extensions of the current method are illustrated in this paper. The object of this study is to develop the surface grid generation and the grid cluster techniques capable of resolving complex flows with shock waves, expansion waves, shear layers. The knot insert method of Non-Uniform Rational B-Spline seems well worked. In addition, NURBS has been widely utilized to generate grids in the computational fluid dynamics community. Computational examples associated with practical configurations have shown the utilization of the algorithm.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2002년도 추계 학술대회논문집
• /
• pp.84-87
• /
• 2002

When computing the flow around complex three dimensional configurations, the generation of grid is the sunt time consuming part of any calculation. The object of this study is to develop the grid duster techniques capable of resolving complex flows with shock waves, expansion waves, shear layers, and cursive shapes, The Dot insert method of Non-Uniform Rational B-Splines is described as a id control method.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2007년도 춘계 학술대회논문집
• /
• pp.108-111
• /
• 2007

A fast and robust method of grid generation to multiple functions has been developed for flow analysis in three dimensional space. It is based on the Non-Uniform Rational B-Spline of an approximation method. The grid generation method, details of numerical implementation. examples of application, and potential extensions of the current method are illustrated in this paper.

• 한국수자원학회논문집
• /
• 제43권1호
• /
• pp.105-117
• /
• 2010

본 논문은 2차원 천수방정식을 해석하기 위해 새롭고 간단한 MUSCL 재구성법을 제안하였다. 수정 MUSCL 기법은 보존변수의 재구성을 위해 계산격자와 인접격자의 보존변수 차에 대해 각 경계면에 균일하게 분배하는 기존 방법 대신 면적가중비를 사용하였으며, 이 방법은 정형격자 뿐만 아니라 비정형 격자의 사용에도 보존변수의 물리적 재구성이 가능하다. 또한, 본 연구에서는 비구조적 격자의 적용이 가능한 차원비분리 기법을 적용하였으며, 수정 MUSCL 기법의 사용으로 발생할 수 있는 수치진동을 제어하기 위해 TVD 기법의 경사제한자를 사용하였다. 하상경사항의 정확하고 효율적인 수치 처리를 위해 수정 MUSCL 기법을 수면경사법과 연계하였다. 제안한 기법을 적용한 유한체적모형을 건물의 영향을 고려한 댐 붕괴 해석 및 Bellos의 댐 붕괴 실험에 적용하고, 적용결과를 실험실 자료 및 기존 연구자의 계산결과와 비교하여 개발모형을 검증하였다.

• 대한수학회보
• /
• 제51권4호
• /
• pp.1087-1100
• /
• 2014

We present an accurate and efficient numerical method for solving the Black-Scholes equation. The method uses an adaptive grid technique which is based on a far-field boundary position and the Peclet condition. We present the algorithm for the automatic adaptive grid generation: First, we determine a priori suitable far-field boundary location using the mathematical model parameters. Second, generate the uniform fine grid around the non-smooth point of the payoff and a non-uniform grid in the remaining regions. Numerical tests are presented to demonstrate the accuracy and efficiency of the proposed method. The results show that the computational time is reduced substantially with the accuracy being maintained.

• Structural Engineering and Mechanics
• /
• 제70권3호
• /
• pp.279-287
• /
• 2019

This paper intends to introduce a near-tip grid refinement and to explore its usefulness in the crack analysis by the natural element method (NEM). As a sort of local h-refinement in FEM, a NEM grid is locally refined around the crack tip showing the high stress singularity. This local grid refinement is completed in two steps in which grid points are added and Delaunay triangles sharing the crack tip node are divided. A plane-state plate with symmetric edge cracks is simulated to validate the proposed local grid refinement and to examine its usefulness in the crack analysis. The crack analysis is also simulated using a uniform NEM grid for the sake of comparison. The near-tip stress distributions and SIFs that are obtained using a near-tip refined NEM grid are compared with the exact values and those obtained using uniform NEM grid. The convergence rates of global relative error to the total number of grid points between the refined and non-refined NEM grids are also compared.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1283-1287
• /
• 2003

Reverse engineering technology refers to the process that creates a CAD model of an existing part using measuring devices. Recently, non-contact scanning devices have become more accurate and the speed of data acquisition has increased drastically. However, they generate thousands of points per second and various types of point data. Therefore. it becomes a important to handle the huge amount and various types of point data to generate a surface model efficiently. This paper proposes a new triangular mesh generation method using 3D grids. The geometric information of a part can be obtained from point cloud data by estimating normal values of the points. In our research, the non-uniform 3D grids are generated first for feature based data reduction based on the geometric information. Then, triangulation is performed with the reduced point data. The grid structure is efficiently used not only for neighbor point search that can speed up the mesh generation process but also for getting surface connectivity information to result in same topology surface with the point data. Through this integrated approach, it is possible to create surface models from scanned point data efficiently.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
• /
• pp.345-346
• /
• 2001

그림 1에서 볼 수 있는 것처럼 신호선을 지지하고 있는 membrane은 SMM line의 전체 크기에 비해 아주 작다. 따라서 uniform grid를 ㅣ용해서 이러한 구조를 해석하게 되면 해석점이 너무 많아져서 많은 메모리를 필요로 하게 되어 일반적인 컴퓨터로는 해석이 어려워지며, non-uniform grid를 사용한다 해도 해석점의 수는 줄일 수 있느나 가장 작은 grid의 크기가 membrane의 크기에 의해서 정해지므로 FDTD 해석에 사용되는 time-step이 아주 작아져서 해석하는데 시간이 오래 걸린게 된다.

• 국제초고층학회논문집
• /
• 제8권4호
• /
• pp.255-264
• /
• 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.

• 한국지구과학회지
• /
• 제39권4호
• /
• pp.317-326
• /
• 2018

Effect of the nonuniform grid on the two-dimensional transport equation was investigated in terms of theoretical analysis and finite difference method (FDM). The nonuniform grid having a typical structure of the numerical weather forecast model was incorporated in the vertical direction, while the uniform grid was used in the zonal direction. The staggered and non-staggered grid were placed in the vertical and zonal direction, respectively. Time stepping was performed with the third-order Runge Kutta scheme. An error analysis of the spatial discretization on the nonuniform grid was carried out, which indicated that the combined effect of the nonuniform grid and advection velocity produced either numerical diffusion or numerical adverse-diffusion. An analytic function is used for the quantitative evaluation of the errors associated with the discretized transport equation. Numerical experiments with the non-uniformity of vertical grid were found to support the analysis.