• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.385-392
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• 2003

Traditional forms of river and coastal structures have become very expensive to build and maintain, because of the shortage of natural rock. Geotextile tubes hydraulically or mechanically filled with dredged materials have been applied in hydraulic and coastal engineering in recent years(shore protection structure, detached breakwater, groins and jetty). Recently, new preliminary design criteria supported by model and prototype tests, and some stability analysis calculations have been studied. In this study, the numerical analysis was performed to investigate the behavior of geotextile tube with various properties of geotextile and hydraulic pumping conditions. Numerical analysis was executed to compare with the results from the large-scale field model tests, and also compared the results of 2-D plane strain analysis and 3-D FEM analysis. A geotextile tube was modeled using the commercial finite element analysis program ABAQUS and the one-quarter of tube was modeled. Behavior of geotextile tube during the hydraulic pumping procedure was analyzed by comparing the large-scale field model test and numerical analysis. The shape variation and maximum tube height between the numerical analysis results and large-scale filed test results are turned out to be a good agreement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.94-99
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• 2001

The numerical simulation of the particle dispersion in the vortical flows provides insight into the mechanism of particle-fluid interaction. The simulation results show that the mixing layers are characterized by the large-scale vortical structures undergoing pairing process. The particle dispersion is strongly influenced by the large-scale structures and the particle sizes. The analysis shows that the mixing layers grows like a step-function.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.208-208
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• 2006

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3367-3382
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• 2023

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian computational fluid dynamics method that has been widely used in the analysis of physical phenomena characterized by large deformation or multi-phase flow analysis, including free surface. Despite the recent implementation of eddy-viscosity models in SPH methodology, sophisticated turbulent analysis using Lagrangian methodology has been limited due to the lack of computational performance and numerical consistency. In this study, we implement the standard and dynamic Smagorinsky model and dynamic Vreman model as sub-particle scale models based on a weakly compressible SPH solver. The large eddy simulation method is numerically identical to the spatial discretization method of smoothed particle dynamics, enabling the intuitive implementation of the turbulence model. Furthermore, there is no additional filtering process required for physical variables since the sub-grid scale filtering is inherently processed in the kernel interpolation. We simulate lid-driven flow under transition and turbulent conditions as a benchmark. The simulation results show that the dynamic Vreman model produces consistent results with experimental and numerical research regarding Reynolds averaged physical quantities and flow structure. Spectral analysis also confirms that it is possible to analyze turbulent eddies with a smaller length scale using the dynamic Vreman model with the same particle size.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.167-170
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• 2003

In this paper, the electromechanical displacements of curved actuators using laminated composites are calculated by finite element method to design the optimal configuration of curved actuators. To predict the pre-stress in the device due to the mismatch in coefficients of thermal expansion, the carbon-epoxy and glass- epoxy as well as PZT ceramic is also numerically modeled by using hexahedral solid elements. Because the modeling of these thin layers causes the numbers of degree of freedom to increase, large-scale structural analyses are performed in a cluster system in this study. The curved shape and pre-stress in the actuator are obtained by the cured curvature analysis. The displacement under the piezoelectric force by an applied voltage is also calculated to compare the performance of curved actuator. The thickness of composite is chosen as design factor.

• International Journal of Aeronautical and Space Sciences
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• 제9권2호
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• pp.79-86
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• 2008

High performance direct-iterative hybrid linear solver for large scale finite element problem is developed. Direct solution method is robust but difficult to parallelize, whereas iterative solution method is opposite for direct method. Therefore, combining two solution methods is desired to get both high performance parallel efficiency and numerical robustness for large scale structural analysis problems. Hybrid method mentioned in this paper is based on FETI-DP (Finite Element Tearing and Interconnecting-Dual Primal method) which has good parallel scalability and efficiency. It is suitable for fourth and second order finite element elliptic problems including structural analysis problems. We are using the hybrid concept of theses two solution method categories, combining the multifrontal solver into FETI-DP based iterative solver. Hybrid solver is implemented for our general structural analysis code, IPSAP.

• 한국지반공학회논문집
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• 제19권5호
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• pp.233-241
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• 2003

최근 들어 지오텍스타일 튜브공법은 과거의 임시공법의 한계를 극복하고 다양한 분야에서 주요적용공법으로 활용이 확대되고 있다. 본 연구에서는 수치해석기법을 활용하여 지오텍스타일 튜브의 시공과정에서의 거동에 대하여 연구를 수행하였으며, 수치해석결과를 기존 연구 발표된 현장 모형시험 결과와 비교 분석하였다. 수치해석은 평면변형해석과 3차원 유한요소해석 기법을 이용하여 채움 과정에서 발생하는 정수압에 따른 지오텍스타일 튜브의 형태변화와 실대형 현장실험 결과를 비교 분석하였다. 또한, 3차원 유한요소해석에서는 정수압과 지오텍스타일의 강성변화에 따른 매개변수 해석을 통하여 지오텍스타일 튜브공법의 3차원 유한요소해석 기법을 제시하였다. 평면변형 해석이론에 의한 수치해석은 지오텍스타일 튜브 전용해석 프로그램인 GeoCoPS(version 2.0)를 활용하였으며, 3차원 유한요소 해석은 범용 유한요소해석 프로그램 ABAQUS(version 5.88)를 이용하였다. 평면변형 해석과 3차원 유한요소해석 결과 모두 실대형 현장실험 결과와 근접한 거동을 나타내었으며 적용토사의 종류 및 해석상의 가정사항으로 약간의 차이점들은 발생하지만 평면변형해석 및 3차원 유한요소해석방법을 통하여 채움과정에서의 지오텍스타일 튜브의 거동을 예측할 수 있다.

• 한국해양공학회지
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• 제14권3호
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• pp.46-54
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• 2000

Three dimensional numerical experiments that included the land-use transformation by the large scale reclamation were used to investigate the mesoscale air flow over the coastal regions. In this paper the surface temperature of the inland was determined through the surface heat budget consideration with inclusion of a layer of vegetation. The vertical diffusion coefficients of momentum, heat and specific humidity in the constant flux layer were taken from the Mellor and Yamada(1975). It has shown that the resulting model is able to reproduce the air circulation in coastal regions, and the simulated characteristics agree with the known properties of this circulation. A series of numerical experiments were then carried out to investigate the diurnal response of the air flow to various types of surface inhomogeneities.

• Interaction and multiscale mechanics
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• 제5권1호
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• pp.27-40
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• 2012

The two-dimensional incompressible flow of a linear viscoelastic fluid we considered in this research has rapidly oscillating initial conditions which contain both the large scale and small scale information. In order to grasp this double-scale phenomenon of the complex flow, a multiscale analysis method is developed based on the mathematical homogenization theory. For the incompressible flow of a linear viscoelastic Maxwell fluid, a well-posed multiscale system, including averaged equations and cell problems, is derived by employing the appropriate multiple scale asymptotic expansions to approximate the velocity, pressure and stress fields. And then, this multiscale system is solved numerically using the pseudospectral algorithm based on a time-splitting semi-implicit influence matrix method. The comparisons between the multiscale solutions and the direct numerical simulations demonstrate that the multiscale model not only captures large scale features accurately, but also reflects kinetic interactions between the large and small scale of the incompressible flow of a linear viscoelastic fluid.

• 한국기계가공학회지
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• 제11권4호
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• pp.147-153
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• 2012

The demands of the large scale machine tools, for instance, such as planomiller, turning machine, boring machine, NC machine, have been gradually increased in recent years. As the performances of machine tools and/or cutting tools are advanced, it is possible to perform high-speed and high-precision cutting works. The effective treatment of wet chip, which is discharged from cutting works, becomes very important problems. Therefore, this study is forced on the design of large scale machine tools using CATIA V5R18 and analysis of cutter, which is considered as essential equipment in large scale machine tools, using MSC.Nastran & MSC.Patran. Especially, the relations between tolerated load of cutter, driving horse power and rpm of driving shaft in chip processing system are investigated through analysis. As the results, the reliability of design could be improved by evaluating simulated numerical values, it showed that tolerated loads of supported part and edged part of cutter are 87,000N and 14,450N, respectively.