• Computational Structural Engineering
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• v.5 no.4
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• pp.103-111
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• 1992

In this paper, liquid sloshing effects in rectangular storage structures for spent fuel under earthquake loadings are investigated. Eulerian and Lagrangian approaches are presented. The Eulerian approach is carried out by solving the boundary value problem for the fluid motion. In the Lagrangian approach, the fluid as well as the storage structure is modelled by the finite element method. The fluid region is discretized by using fluid elements. The (1*1)-reduced integration is carried out for constructing the stiffness matrices of the fluid elements. Seismic analysis of the coupled system is carried out by the response spectra method. The numerical results show that the fluid forces on the wall obtained by two approaches are in good agreements. By including the effect of the wall flexibility, the hydrodynamic forces due to fluid motion can be increased very significantly.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.167-170
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• 2004

본 논문에서는 수중익 버블 캐비테이션과 날개 끝 볼텍스 캐비테이션의 거동 및 소음을 Eulerian-Lagrangian 기법을 이용하여 수치적으로 해석하였다. Eulerian-Lagrangian 기법은 캐비테이션 버블이 유동장에 미치는 영향이 거의 없다는 가정하에 유동장과 캐비테이션 거동을 일방으로 연계하여 해석하는 방식이다. 수중익 버블 캐비테이션 해석을 위한 유동장은 비압축성 RAMS 방정식을 해석하여 구하고 날개 끝 볼텍스 캐비테이션 유동장은 일반적 CFD 기법의 큰 수치 소산으로 그 특성이 잘 나타나지 않으므로 Sculley 볼텍스 모델을 이용하여 해석한다. 해석한 유동장 정보를 입력치로 하고 버블의 지배 방정식인 Rayleigh-Plesset 방정식과 Newton의 제2법칙에 근거한 궤적 방정식을 연계하여 캐비테이션의 성장-붕괴와 운동을 예측한다. 계산된 거동 정보를 이용하여 버블 캐비테이션과 날개 끝 볼텍스 캐비테이션의 소음을 예측하였다. 본 연구는 수중 운동체에서 발생하는 캐비테이션의 거동과 소음의 특성을 파악하고 그에 따른 대비책을 마련하는 기본 연구로서 활용할 수 있을 것이다.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.49-55
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• 2016

Electrohydraulic forming (EHF) is a high-speed forming process that uses an electric arc discharge in water. Shock waves resulting from the electric arc discharge are propagated to the blank through water and the blank moves toward the die. Advantages of EHF include improved formability due to the high-speed process and reduction of the bouncing effect. In the current study, a numerical simulation of EHF was developed using LS-DYNA. In the simulation, the model for the electric arc was assumed as an adiabatic gas expansion and an Arbitrary Lagrange-Eulerian (ALE) multi material formulation was used to describe the interaction between the electric arc and the water. In order to model the Fluid-Structure Interaction (FSI), a coupling mechanism was used. The blank of Al 1100-O was simulated using shell elements. The results of the simulation showed that the blank was deformed due to the pressure propagation of water and the bouncing effect did not affect the formability of blank.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.471-474
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• 2006

The Mixer is apparatus that help precipitation or an inhomogeneous distribution of various phases to be mixed and that user makes necessary material mixing one or the other. Mainly the mixer which is used from chemical and food industry is very important system in engineering that mixes the material. The inside flow of the mixer under the actual states which put a basis in flow of the fluid is formed rotation of the impeller. The inside flow of impeller will be caused by various reasons change with shape of impeller, number of rotation, mixing material and flow pattern of free surface etc. Also mixer study depended in single-phase flow and experimental research. So the numerical analysis of flow mixing solid-fluid particle is simulated. It is become known, that the case where agitator inside working fluid includes the solid particle the sinkage reverse which the solid particle has decreases an agitation efficiency. From the research which it sees the hazard solid which examines the effect where the change of the sinkage territory which it follows agitation number of revolution and diameter of the particle goes mad to an agitator inside flow distribution - numerical analysis the inside flow distribution of liquid state with Eulerian Two-Phase Method.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.2
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• pp.73-82
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• 1998

In order to simulate surface discharged heat dispersion in costal area, a 2-dimensional Eulerian-Lagrangian model for far field and semi-active particle tracking random walk model in near field has been combined. The mass of discharged heat water in near field has treated as particles with buoyancy and this is eventually converted to horizontal additive dispersion in random walk equations. This model is applied to both a simplified coastal geometry and a real site. In simple application it can simulate plume-like characteristics around discharging point than a near field-model, CORMIX/3. Actual application in the Chonsu Bay shows farther spreading of heat water in near field comparing the observed data, and this shows that the developed model might be applied with satisfaction.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.65-72
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• 2011

Numerical simulation has been performed to investigate the bubbly flow in the liquid with vertical temperature gradient. The objective of this study is to establish an accurate numerical prediction program of gas-liquid two-phase flows in a vertical temperature gradient condition, whose mathematical model is formulated by the Eulerian-Lagrangian model. The present numerical results reveal the temperature mixing mechanism and the fluid dynamical characteristics induced by the bubbly flow in the liquid with stratified temperature. The effects of bubble radius, void fraction, and gas flow rate on bubble-driven convective flow are considered, too.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.269-272
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• 2008

Blast load, an impulsive load with extremely short time duration with very high pressure, is effected by ground and air condition, weight of charge, shape and location of structure. In this study, a blast dynamic analysis for the air-structural integrated model considering dynamic properties of materials and simulation of complex blast wave propagation by Arbitrary Lagrangian- Eulerian technique is suggested to perform an accurate blast analysis of concrete structures. For the verification of the proposed blast analysis method, which is the air-structure integrated model using ALE technique, the comparison of analysis and experimental results is performed. The verification confirms that the simulation of realistic behavior of RC wall structures is possible using ALE method. Also, the example cases which have been analyzed using this method show that the estimation to the structural failure criterion for blast load failure can be represented by energy absorbtion procedure.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4395-4407
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• 2023

Bubble columns are widely encountered in several industries, especially in the field of nuclear safety. The Eulerian-Eulerian and the Eulerian-Lagrangian methods are commonly used to investigate bubble columns. Eulerian approaches require additional tasks such as strict volume conservation at the interface and a predefined well-structured grid. In contrast, the Lagrangian approach can be easily implemented. Hence, we introduce a fully Lagrangian approach for the simulation of bubble columns using the discrete bubble model (DBM) and moving particle semi-implicit (MPS) methods. Additionally, we propose a rigorous method to estimate the volume fraction accurately, and verified it through experimental data and analytical results. The MPS method was compared with the experimental data of Dambreak. The DBM was verified by analyzing the terminal velocity of a single bubble for each bubble size. It agreed with the analytical results for each of the four drag correlations. Additionally, the improved method for calculating the volume fraction showed agreement with the Ergun equation for the pressure drop in a packed bed. The implemented MPS-DBM was used to simulate the bubble column, and the results were compared with the experimental results. We demonstrated that the MPS-DBM was in quantitative agreement with the experimental data.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.350-362
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• 2017

The Eulerian nearshore current model is more advantageous than the Lagrangian model in the way that numerical results from the Eulerian model can be directly compared with the measurements by the stationary equipment. It is because the wave mass flux is not included in the computed mass flux of Euleran nearshore current model. In addition, the Eulerian model can simulate the longshore currents with depth varying parabolic profile. However, the numerical models proposed by different researcher have different forms of the wave stress terms. For example, wave stresses in Newberger and Allen's (2007) model is constant over the depth, while those of Chun (2012) are vertically distributed. In the present study, these wave stress terms were compared against Hamilton et al.'s (2001) laboratory experiments to see the effects of different wave stress terms performed on the computation of nearshore currents.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.39-45
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• 2012

In the standard CFD code, Lagrangian-Eulerian method is very popular to simulate the liquid spray penetrating into gaseous phase. Though this method can give a simple solution and low computational cost, it have been reported that the Lagrangian spray models have numerical grid dependency, resulting in serious numerical errors. Many researches have shown the grid dependency arise from two sources. The first is due to unaccurate prediction of the droplet-gas relative velocity, and the second is that the probability of binary droplet collision is dependent on the grid resolution. In order to solve the grid dependency problem, the improved spray models are implemented in the KIVA-3V code in this study. For reducing the errors in predicting the relative velocity, the momentum gain from the gaseous phase to liquid particles were resolved according to the gas-jet theory. In addition, the advanced algorithm of the droplet collision modeling which surmounts the grid dependency problem was applied. Then, in order to validate the improved spray model, the computation is compared to the experimental results. By simultaneously regarding the momentum coupling and the droplet collision modeling, successful reduction of the numerical grid dependency could be accomplished in the simulation of the high-pressure injection diesel spray.