• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.108-114
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• 1999

In this paper. a new automatic multi=block grid generation technique for general 2D regions is introduced. According to this simple and robust method, the domain of interest is first triangulated by using Delaunay triangulation of boundary points, and then geometric information of those triangles is used to obtain block topology. Once block boundaries are obtained. structured grid for each block is generated such that grid lines have $C^0-continuity$ across inter-block boundaries. In the final step of the present method, an elliptic grid generation method is applied to smoothen grid distribution for each block and also to re-locale the inter-block boundaries, and eventually to achieve a globally smooth multi-block structured grid system with $C^1-continuity$.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.157-162
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• 2005

Parallel implementation and performance assessment of the grid assembly in a structured chimera grid approach is studied. The grid assembly process, involving hole cutting and searching donor, is parallelized on the PC cluster. A message passing programming model based on the MPI library is implemented using the single program multiple data(SPMD) paradigm. The coarse-grained communication is optimized with the minimized memory allocation because that the parallel grid assembly can access the decomposed geometry data in other processors by only message passing in the distributed memory system such as a PC cluster. The grid assembly workload is based on the static load balancing tied to flow solver. A goal of this work is a development of parallelized grid assembly that is suited for handling multiple moving body problems with large grid size.

• International Journal of High-Rise Buildings
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• v.8 no.4
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.5
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• pp.1074-1079
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• 2004

So far, many sensors such as a structured grid pattern generator, a laser, and CCD camera to obtain 3D information have been used, but most of algorithms for a calibration are inefficient since a huge memory and experiment time are required. In this paper, the calibration algorithm of a structured grid pattern based on triangulation method is introduced to calculate 3D information in the real world. The beams generated from structured grid pattern generator established horizontally with the CCD camera are projected on the calibration plat. A CCD camera measures the intersection plane of a projected beam and an object plane. The 3D information is calculated using measured and calibration datum. This proposed method in this paper has advantages such as a memory saving and an efficient experimental time since the 3D information is obtained simply the triangulation method.

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.28-37
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• 2007

In this study, a multi-block structured grid deformation code based on a hybrid of a transfinite interpolation algorithm and spring analogy was developed. The configuration was modeled by a Bezier surface. A combination of the spring analogy for block vertices and the transfinite interpolation for interior grid points helps to increase the robustness and makes it suitable for distributed computing. An elliptic smoothing operator was applied to the block faces with sub-faces in order to maintain the grid smoothness and skewness. The capability of this code was demonstrated on a range of simple and complex configurations including an airfoil and a wing-body configuration.

• 한국전산유체공학회:학술대회논문집
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• 2006.05a
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• pp.299-300
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• 2006

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.36-42
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• 2016

One of the obstacles on the grid generation for complex geometries with multi-block structured grids is the domain decomposition. In this paper, the domain decomposition for two-dimensional flow is studied using the flow characteristics. The potential flow equation with the source distribution on the panel surface is solved to extract the information of the flow. The current approach is applied to a two-dimensional cylinder and Bi-NACA0012 problems. The generated grids are applied to generic flow solvers and reasonable results are obtained. It can be concluded that the current methods is useful in the domain decomposition for the multi-block structured grid.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.335-340
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• 2010

In this paper development of an automatic grid generation program for flow field calculation around 3D wing is described and its application is also introduced. The program is developed by using JAVA programming language and a graphic library, JOGL, and it can be usee either as an application program on a local computer or as a applet in the network environment. Currently, The program provides NACA series 4-digit airfoils as the wing cross-section shape and it offers a non-complicated GUI program which can easily generate structured grids for wings based on user's parameter input. Grid generated by the program can be selected as one of two types; O-type and C-type. In this research advancing layer method(ALM) augmented by elliptic smoothing method is used for the FLUENT. It is shown that by using current program high-quality structured grids around 3D wings can be easily generated, and typical grid generation results and flow solutions are demonstrated. Study on effects of geometric parameters on flow field is also tried by changing major wing parameters such as incidence angle type of wing-tip and sweepback angle.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.136-142
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• 2008

The influence of different grids on numerical prediction of subsonic compressor performance and stall was investigated. Two types of grids were examined, structured H type grid and structured O-H type grid. Evaluations were conducted by comparing the numerical results with experimental results obtained from a low-speed single-stage rig test for a new concept compressor, called diffuser passage compressor, aiming at improving tip clearance sensitivity. At low mass flow operating conditions, the numerical calculation with O-H type grid showed that the lowest mass flow operating point for which the calculation was able to converge was almost the same as the lowest steady mass flow obtained from the rig test. On the other hand, the numerical calculation with structured H type grid diverged at higher mass flow operating point. It was found that this difference was attributed to the effect of double-valuedness of H type grid that existed at leading edge on the boundary layer development on the blade surface.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.47-57
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• 2019

Recent CFD solvers in engineering have to treat geometrically complex domains and moving body problems. In ship hydrodynamics, flow around the stern and ship motions in waves are examples of such cases mentioned before. The unstructured grid scheme is successfully applied for these problems, but it has weakness of inefficient memory usage and intensive computational time as compared to the structured grid method. Overset grid scheme is one of the alternatives for structured grid system taking advantage of fast and memory efficiency. Overset grid scheme is especially useful for moving body problem because there is no need to re-mesh around the body. In this paper, we adopted the Suggar++, the grid connectivity and interpolation utility for the overlapping grid, to WAVIS which is the in-house flow solver of KRISO. Then we introduced some applications using the overset grid method for flow analysis around the ships. The computed results show that WAVIS with Suggar++ is practically feasible and has an advantages for moving geometry cases.