• 대한기계학회논문집A
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• 제29권5호
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• pp.671-679
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• 2005

A method of generation boundary layer mesh has been presented. This paper describes the generation of semi-unstructured prismatic/tetrahedral meshes for three-dimensional geometries with thin thickness. By of fretting of surface triangle elements prismatic/tetrahedral meshes are generated and using the node relocation method of this research intersected meshes can be efficiently improved. Finally tetrahedral meshes are automatically generated at the rest of the domain. Sample meshes are constructed to demonstrate the mesh generating capability of the proposed algorithm.

• 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 Re_θ=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.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1999년도 학술대회
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• pp.9-14
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• 1999

The object boundary of an image plays an important role for image interpretation. In this paper, we introduce a concept of hierarchical mesh-based image segmentation for finding object boundaries. In each hierarchical layer, we employ neighborhood searching and boundary tracking methods to refine the initial boundary estimate. We also apply a local region growing method to define closed contours. Experimental results indicate that reliable segmentation of objects can be accomplished by the pro-posed tow complexity technique.

• 대한수학회논문집
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• 제14권4호
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• pp.815-832
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• 1999

High-order weighted difference schemes with uniform meshes are considered for the convection-diffusion problem depending on Reynolds numbers. For small Reynolds numbers, a weighed cen-tral difference scheme is suggested since there is no boundary layer. For large Reynolds numbers, we propose a modified up wind method with an artificial diffusion in order to overcome nonphysical oscilla-tion of central schemes and obtain good accuracy in the boundary later. Existence and corresponding error estimates of the solution for the difference scheme have been shown. Numerical experiments are provided to back up the analysis.

• 한국CDE학회논문집
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• 제11권2호
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• pp.107-114
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• 2006

A new quadrilateral mesh generation technique from an existing triangle mesh is proposed in this paper. The proposed method is based on advancing front method and zero-thickness layer. Beginning with an initial triangular mesh, boundary triangular elements are removed and quadrilateral elements with zero thickness are generated. A quality of quadrilateral elements is improved during a mesh smoothing process. Until all initial triangular elements are removed, this procedure is repeated. Sample meshes are constructed to demonstrate the mesh generation capability of proposed algorithm.

• Advances in aircraft and spacecraft science
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• 제4권5호
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• pp.555-571
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• 2017

The description of transitional flows by means of RANS equations is sometimes based on non-local approaches which require the computation of some boundary layer properties. In this work a non-local Laminar Kinetic Energy model is used to predict transitional and separated flows. Usually the non-local term of this model is evaluated along the grid lines of a structured mesh. An alternative approach, which does not rely on grid lines, is introduced in the present work. This new approach allows the use of fully unstructured meshes. Furthermore, it reduces the grid-dependence of the predicted results. The approach is employed to study the transitional flows in the T106c turbine cascade and around a NACA0021 airfoil by means of a discontinuous Galerkin method. The local nature of the discontinuous Galerkin reconstruction is exploited to implement an adaptive algorithm which automatically refines the mesh in the most significant regions.

• 한국전산유체공학회지
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• 제1권1호
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• pp.19-25
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• 1996

A multiblock grid generation has been developed to be reliably used for a Navier-Stokes simulation of the turbomachinery flow-fields A multiblock structure simplifies the creation of structured H-grids about complex turbomachinery geometries and facilitate the creation of a grid in the tip flow region. The numerical algorithm adopts the combination of the algebraic and elliptic method to create the internal grids efficiently and quickly. The grid refinement process is enhanced by developing strategies to utilized Bezier curves and splines along with weighted transfinite interpolation technique and by formulating the grid-imbedding method for the viscous boundary-layer meshes. For purposes of illustration, the grid generator is applied to the high turning turbine rotor blades. Two different types of computational grids are provided to be compared with respect to the grid adaptation to the flow simulations. Extension to three-dimensions was done to show the possibility of its application to the tip-flow simulations. The grid quality of the multiblock structure is good in the passages, with gloval orthogonality and adequate smoothness.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 가을 학술발표회 논문집
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• pp.42-49
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• 1997

In this paper, the method for soil-structure interaction analyses in the time domain is proposed. The far field soil region which is the outside of the artificial boundary is modeled by using explicit frequency-dependent two dimensional infinite elements which can include multiple wave components propagating into the unbounded medium. Since the dynamic stiffness matrix of the far field soil region using the proposed infinite elements is obtained explicitly in terms of exciting frequencies and constants in the frequency domain, the matrix can be easily transformed into the displacement unit-impulse response matrix, which corresponds to a convolution integral of it in the time domain. To verify the proposed method for soil-structure interaction analyses in the time domain, the displacement responses due to an impulse load on the surface of a soil layer with the rigid bed rock are compared with those obtained by the method in the frequency domain and those by models with extend finite element meshes. Good agreements have been found between them.