• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.7 s.262
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• pp.739-746
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• 2007

Recently, models in STL files are widely used in reverse engineering processes, CAD systems and analysis systems. However the models have poor geometric quality and include only triangles, so the models are not suitable for the finite element analysis. This paper presents a general method that generates finite element mesh from STL file models. Given triangular meshes, the method estimates triangles and makes clusters which consist of triangles. The clusters are merged by some geometric indices. After merging clusters, the method applies plane meshing algorithm, based on domain decomposition method, to each cluster and then the result plane mesh is projected into the original triangular set. Because the algorithm uses general methods to generate plane mesh, we can obtain both tri and quad meshes unlike previous researches. Some mechanical part models are used to show the validity of the proposed method.

• Journal of Navigation and Port Research
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• v.34 no.5
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• pp.367-373
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• 2010

When the numerical analysis is carried out, it is necessary to set proper elements as a feature of analysis domains for more accurate simulations. In this study, Distinct Element Method(DEM) is applied, only considering repulsive force and tensile force except for frictional force and resisting force of particle. When the filled particles with initial Quad-tree type is relocated by DEM, a blank space existing among the particles can be minimized because the shape of particle is circular. Finally, it is the effective feature that the centroidal disposion of the particles is similar to an equilateral triangle. Triangular mesh are formed by using the Delaunay triangular technique on these relocated particles, the quality of triangular mesh is more improved by carrying out Laplace interpolations. The compared result of Aspect Ratio before and after the Laplace interpolation is shown that although the quality of triangular mesh made by DEM is good, the later triangular mesh are higher quality than the formers. In this study, although the developed technique takes a longer calculational time than the previous technique to generate triangular mesh, it is considered that the applicable possibility is very high in the generation of finite element mesh about wave analysis and various numerical simulation to need a complex or reappearance of exact topography.

• Journal of Aerospace System Engineering
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• v.15 no.2
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• pp.10-15
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• 2021

The propeller wake of tiltrotor-type aircrafts, such as TR-60 and quad tilt propeller (QTP) UAV, in hover substantially impinges the upper surface of the primary wing and generates a downward load. This load is directly proportional to the thrust of the propeller and reduces the available payload. Therefore, wing and nacelle mechanisms should be carefully designed to reduce downward load. This study conducted a numerical analysis of the rotating propeller in hover to predict the downward load of a QTP UAV. An unsteady three-dimensional Navier-Stokes solver was used along with a sliding mesh for the simulation of the rotating propeller. To reduce the downward load, the tilting mechanisms of the partial wing and nacelle were simultaneously introduced and numerically analyzed. Finally, the downward load was predicted by 14% of isolated propeller thrust; further, the downward load could be reduced by adopting the partial wing and nacelle tilting concept.

• Journal of the Korea Computer Graphics Society
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• v.16 no.3
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• pp.31-39
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• 2010

The particle system based on quad mesh has been posed to model cloth. But we need to develop cloth models on triangular meshes because they are widely used. Cloth modeling on triangular mesh is often done in the style of finite element method, which assumes that material is continuous. To preserve the advantages of particle system, e.g. model simplicity and the ease of implementation, even on triangular mesh, this paper proposes a particle system on triangular mesh. The motion of cloth is modeled so that vertices interact with each other via the edges on the triangular mesh. The interactions of vertices are assumed to exist between every adjacent vertex and between every other vertex. The deformation energy due to interaction is constructed based on the theory of elasticity. The contribution of the paper is to implement the advantages of particle system on triangular mesh.

• Korean Journal of Computational Design and Engineering
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• v.11 no.1
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• pp.41-48
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• 2006

This paper describes hexahedral mesh generation for various shell structures, such as automobile bodies, plastic injection mold components and sheet metal parts by using chordal surfaces. After generaling one-layered tetrahedral mesh by an advancing front algorithm, the chordal surfaces are constructed by cutting of tetrahedral elements. Since the choral surfaces are composed of tri/quad elements with poor quality, they are transformed into quadrilateral elements with good quality. Hexahedral elements are then generated by offsetting these quadrilateral elements. The boundary nodes of hexahedral elements are generated on the outer surfaces of the original shell structures. Sample models including nonuniform thickness have been tested to validate the proposed algorithm.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.1
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• pp.81-88
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• 2014

Accurate wind data is essential for predicting airborne spread of virus. OpenFOAM was used for computational fluid dynamics (CFD) simulation procedure which is under GNU GPL (General Public License). Using complex terrain, DEM (Digital Elevation Map) that was prepared from GIS information covering a research site is converted to a three dimensional surface mesh that is composed by quad and full hexahedral space meshes. Around this surface mesh, an extended computational domain volume was designed. Atmospheric flow boundary conditions were used at inlet and roughness height and was considered at terrain by using rough wall function. Two different wind conditions that was relatively stable during certain periods were compared in 3 different locations for validating the accuracy of the CFD computed solution. The result shows about 10 % of difference between the calculated result and measured data. This procedure can simulate a prediction of time-series data for airborne virus spread that can be used to make a web-based forecasting system of airborne virus spread.

• Journal of the Korea Computer Graphics Society
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• v.22 no.2
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• pp.1-10
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• 2016

The computational cost of clothing simulation and rendering is mainly depends on the type of mesh and its quality. Thus, quadrilateral meshes are generally preferred over triangular meshes for the reasons of accuracy and efficiency. This paper presents a method of quadrangulating sewing pattern based on the recursive geometry decomposition method. Herein, we proposed two simple improvements to the previous algorithms. The first one deals with the recursive geometry decomposition in which the physical domain is decomposed into simple and mappable regions. The second proposed algorithm deals with the vertex validation in which the invalid vertex classification can be validated.

• Journal of Korea Multimedia Society
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• v.17 no.1
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• pp.69-76
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• 2014

It is hard to represent massive terrain data in real-time even using recent graphics hardware. In order to process massive terrain data, mesh simplification method such as continuous Level-of-Detail is commonly used. However, existing GPU-based methods using quad-tree structure such as geometry splitting, produce lots of vertices to traverse the quad-tree and retransmit those vertices back to the GPU in each tree traversal. Also they have disadvantage of increase of tree size since they construct the tree structure using texture. To solve the problem, we proposed GPU-base chunked LOD technique for real-time terrain rendering. We restrict depth of tree search and generate chunks with tessellator in GPU. By using our method, we can efficiently render the terrain by generating the chunks on GPU and reduce the computing time for tree traversal.