• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.751-756
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• 2014

The dynamic behavior of numerous grains interacting with each other can be easily observed. In this study, this dynamic behavior was analyzed based on the contact between numerous grains. The discrete element method was used for analyzing the dynamic behavior of each particle and the neighboring-cell algorithm was employed for detecting their contact. The Hertzian and tangential sliding friction contact models were used for calculating the contact force acting between the particles. A GPU-based parallel program was developed for conducting the computer simulation and calculating the numerous contacts. The dam break experiment was performed to verify the simulation results. The reliability of the program was verified by comparing the results of the simulation with those of the experiment.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.31-35
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• 2013

The objective of this study is numerically analyzed the behavior characteristics of the magnetic fluid in a closed rectangular container using finite element method (FEM). The governing equations are solved with magnetization and Maxwell equations for consideration of rotating effect of the magnetite particle. Then the discretized equations are solved with boundary conditions of the velocity and temperature. The developed model is validated with the results of Davis (1983) and Fusegi et al. (1991) has a good agreement within 5.5 % and 2.7 %, respectively.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.539-546
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• 2003

The numerical model of the flow analysis by finite element technique is described. The Galerkin method is employed for spatial discretization Two step explicit finite element scheme is used to discretize the time function, which has advantage in problems treating large numbers of elements and unsteady state. Two dimensional hydrodynamic model considering moving boundary condition is developed. Also it applied flow model which develop on flow portion of ideal fluid in the model flume and verified, and the results of this study confirm the efficiency of moving boundary treatment in Jeju harbor. The computed results have shown the good adaptability of moving boundary condition From these studies, it can be concluded that the present method is a useful and effective tool in tidal flow analysis.

• Geotechnical Engineering
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• v.6 no.1
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• pp.25-34
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• 1990

The finite element and boundary element methods of underground analysis are both well established numerical techniques for determination of stress and displacement distributions at underground excavation. The finite element method presents antithetical advantages and limitations. Complex constitutive behaviour may be modelled, at the expense of numerical efficiency and, for infinite domain, inadequate representation of remote bounadry conditions. The inherent advantages of the boundary element method are the ease with which infinite domain problems may be analysed, and the efficiency of analysis typically associated with a boundary value solution procedure. Application of the method is limited by the requirements linear constitutive behaviour for the medium. A combined of the finite element and boundary element methods of underground analysis is shown to preserve the advantages of each procedure, and, eliminates their individual disadvantages. Procedures employed in this papers described combined FEBEM algorithm. Solutions of underground excavation verifying the performance of combined FEBEM code are compared with theoretical solution, boundary element solution and finite element solution.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.65-74
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• 2003

This paper presents the results of a comparative study between FEM and LEM on slope stability analysis. For validation, factors of safety were compared between FEM and LEM. The results from the two methods were in good agreement. This suggests that the FEM with the shear strength reduction method can be effectively used on slope stability analyses. A series of analyses were then performed using the FEM for various constitutive laws, slope angles, flow rules, and the finite element discretizations. Among the findings, the finite element method in conjunction with the shear strength reduction method can provide reasonable results in terms of safety. Also revealed is that the results of FEM can be significantly affected by the way in which the type of constitutive law and flow nile we selected.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.3
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• pp.291-299
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• 2008

The present study is to estimate the effects of diffracted wave fields in a harbor and around harborentrance due to random waves, when a navigation channel is dredged in the vicinity of the a harbor entrance. The cross sections of harbor boundary are considered to be partial or full reflection in this study. The numerical simulation has been performed by the boundary element method, which is to discrete segments of pit- and harbor- boundary with the algorism of auto generated elements. The incident wave conditions are specified using discretized forms of the Mitsuyasu's frequency spectrum and directional function. The results of the present numerical simulation agreed well with those of the published experimental data. It is shown that the ratios of wave height reduction are about 20% for the case of fully reflecting boundary, and 10% for the case of partially reflecting boundary by the effect of placing a pit, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.465-474
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• 2012

In this study, a dynamic simulation model that considers many spherical particles and multibody dynamics (MBD) entities is developed. Plenteous spherical particles are solved using the Discrete Element Method (DEM) technique and simulated on a GPU board in a PC. A fast algorithm is used to calculate the Hertzian contact forces between many spherical particles, and NVIDIA CUDA is used to increase the calculation speed. The explicit integration method is applied to solve the many spheres. MBD entities are simulated by recursive formulation. Constraints are reduced by recursive formulation, and the implicit generalized alpha method is applied to solve the dynamic model. A new algorithm is developed to simulate the DEM and MBD models simultaneously. As a numerical example, a truck car model and gear model are developed. The results show that the proposed algorithm using a general-purpose GPU in a PC has many advantages.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.4
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• pp.363-370
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• 2017

This paper is concerned with the evaluation of mixing performance of a particle mixer, which consists of a vertical cylindrical vessel and a rotating impeller with several blades. We consider four design variables for the mixer blades, such as the angle, length, and number of blades, and the gap between the blades and the vessel bottom. The particle mixing process due to the impeller rotation is simulated using the discrete element method, and the mixing performance is quantitatively evaluated by introducing a mixing index. Analyzing the main effects and interactions of the four design variables through the design-of-experiments approach, it is concluded that the blade angle has the most dominant influence on the mixing performance whereas the gap has no significant influence. In addition, we determine the best combination of design parameters to maximize the mixing performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.1-8
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• 1992

This paper presents a p-version finite element approach for modeling the stress distribution around a circular hole in a finite strip subjected to membrane and flexural behaviors. Also, same problem with a crack emanating from a perforated tension strip was solved by virtual crack extension method. The p-version of the finite element method based on integrals of Legendre polynomials is shown to perform very well for modeling geometries with very steep stress gradients in the vicinity of a circular cutout. Here, the transfinite mapping technique for circular boundaries was used to avoid the discretization errors. The numerical results from the proposed scheme have a good comparison with those by Nisida, Howland, Newman etc. and the conventional finite element approach.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.2 s.42
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• pp.47-58
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• 2005

Dynamic response analysis in time dimain is conducted for floating bridges with discrete pontoons subject to spatial variation of ground motions. The Spatial variation of ground motions is considered with the coherency function model which represents wave passage, incoherence and local site effects. The superstructure of the bridge is represented by space frame and elastic catenary cable elements, the abutment us modelde with the spring element of FHWA guideline for considering soil structure interaction and the concept of retardation function is utilized to consider the frequency dependency of the hydrodynamic coefficients which are obtainde by boundary element method. multiple support excitations considering the spatial variation. The noticeable amplification of the response can be shown when the spatial variation of ground motions is incorporated in the anallysis of floating bridges.