• Structural Engineering and Mechanics
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• v.38 no.5
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• pp.633-649
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• 2011

The paper presents a study aimed at understanding some characteristics of an interior explosion within a room with limited or no venting. The explosion may occur in ammunition storage or result from a terrorist action or from a warhead that had penetrated into this room. The study includes numerical simulations of the problem and analytical derivations. Different types of analysis (1-D, 2-D and 3-D analysis) were performed for a room with rigid walls and the results were analyzed. For the 3D problem the effect of the charge size and its location within the room was investigated and a new insight regarding the pressure distribution on the interior wall as function of these parameters has been gained. The numerical analyses were carried out using the Eulerian multi-material approach. Further, an approximate analytical formula to predict the residual internal pressure was developed. The formula is based on the conservation law of total energy and its implementation yields very good agreement with the results obtained numerically using the complete statement of the problem for a wide range of explosive weights and room sizes that is expressed through a non-dimensional parameter. This new formula is superior to existing literature recommendations and compares considerably better with the above numerical results.

• Structural Engineering and Mechanics
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• v.62 no.2
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• pp.163-170
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• 2017

This study presents a particle-wall filtration model for predicting the particle motion behavior in a typical rotational flow field-filtration in blower system of cooker hood. Based on computational fluid dynamics model, air flow and particles has been simulated by Lagrangian-particle/ Eulerian-gas approaches and get verified by experiment data from a manufacturer. Airflow volume, particle diameter and local structure, which are related to the particle filtration has been studied. Results indicates that: (1) there exists an optimal airflow volume of $1243m^3/h$ related to the most appropriate filtration rate; (2) Diameter of particle is the significant property related to the filtration rate. Big size particles can represent the filtration performance of blower; (3) More than 86% grease particles are caught by impeller blades firstly, and then splashed onto the corresponding location of worm box internal wall. These results would help to study the micro-particle motion behavior and evaluate the filtration rate and structure design of blower.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1348-1358
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• 2004

The filling pattern and an adaptive grid refinement based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation fur flow analysis is Navier-Stokes equation including inertia and gravity effects. The mixed FE formulation and predictor-corrector method are used effectively for unsteady numerical simulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among seven filling patterns at each tetrahedral control volume. By adaptive grid refinement, the new flow field that renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. The collapse of a water dam and the filling of a fluidity spiral have been analyzed. The numerical results have been in good agreement with the experimental results and the efficiency of the adaptive grid refinement and filling pattern techniques have been verified.

• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.91-96
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• 2016

From the Earth's polar motion time series (IERS 08 C04, since 1981), after removal of seasonal variation by band-pass filtering, we acquired Earth's free Eulerian motion (Chandler wobble) time series. By successive least square error fittings on it, we analyzed amplitude and phase variation of Chandler wobble. We attempted to identify any precursory behavior of the pole before large earthquakes but only to fail. Unlike Smylie's conjecture there was no appreciable motion of the Earth's pole detected at around the each times of recent six largest earthquakes of magnitude over 8.5.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.19-23
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• 2010

Nanoimprint lithography (NIL) is one of the most versatile and promising technology for micro/nano-patterning due to its simplicity, high throughput and low cost. Recently, one of the major trends of NIL is large-area patterning. Especially, the research of the application of NIL to TFT-LCD field has been increasing. Technical difficulties to keep the uniformity of the residual layer, however, become severer as the imprinting area increases. In this paper we performed a numerical study for a large area NIL (the $2^nd$ generation TFT-LCD glass substrate ($370{\times}470$ mm)) by using finite element method. First, a simple model considering the surrounding wall was established in order to simulate effectively and reduce the computing time. Then, the volume of fluid (VOF) and grid deformation method were utilized to calculate the free surfaces of the resist flow based on an Eulerian grid system. From the simulation, the velocity fields and the imprinting pressure during the filling process in the NIL were analyzed, and the effect of the surrounding wall and the uniformity of residual layer were investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.186-191
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• 2004

The reactive flowfield of the transverse injecting combustor has been studied using Euler-Lagrange method in order to develop an efficient solution procedure for the understanding of liquid spray combustion in the transverse injecting combustor which has been widely used in ramjets and turbojet afterburners. The unsteady two-dimensional gas-phase equations have been represented in Eulerian coordinates and the liquid-phase equations have been formulated in Lagrangian coordinates. The gas-phase equations based on the conservation of mass, momentum, and energy have been supplemented by combustion. The vaporization model takes into account the transient effects associated with the droplet heating and the liquid-phase internal circulation. The droplet trajectories have been determined by the integration of the Lagrangian equation in the flow field obtained from the separate calculation without considering the iterative effect between liquid and gas phases. The reported droplet trajectories had been found to deviate from the initial conical path toward the flow direction in the very end of its lifetime when the droplet size had become small due to evaporation. The integration scheme has been based on the TEACH algorithm for gas-phase equation, the second order Runge-Kutta method for liquid-phase equations and the linear interpolation between the two coordinate systems. The calculation results has shown that the characteristics of the droplet penetration and recirculation have been strongly influenced by the interaction between gas and liquid phases in such a way that most of the vaporization process has been confined to the wake region of the injector, thereby improving the flame stabilization properties of the flowfield.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.451-455
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• 2017

The reactive Eulerian-Lagrangian code is utilized to simulate combustion of ZPP/THPP in a closed vessel. In the paper, ignition delay of THPP is mainly studied since ZPP and THPP are isolated by a boron nitride wall. Only a numerical case study is conducted as experimental observation is inaccessible. Results showed THPP ignition delay affects initial shock strength thus not only the first peak become weak, but also the frequency of a pressure oscillation is slowed.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.72-86
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• 2016

A steam explosion may occur during a severe accident, when the molten core comes into contact with water. The pressurized water reactor and boiling water reactor ex-vessel steam explosion study, which was carried out with the multicomponent three-dimensional Eulerian fuel-coolant interaction code under the conditions of the Organisation for Economic Co-operation and Development (OECD) Steam Explosion Resolution for Nuclear Applications project reactor exercise, is presented and discussed. In reactor calculations, the largest uncertainties in the prediction of the steam explosion strength are expected to be caused by the large uncertainties related to the jet breakup. To obtain some insight into these uncertainties, premixing simulations were performed with both available jet breakup models, i.e., the global and the local models. The simulations revealed that weaker explosions are predicted by the local model, compared to the global model, due to the predicted smaller melt droplet size, resulting in increased melt solidification and increased void buildup, both reducing the explosion strength. Despite the lower active melt mass predicted for the pressurized water reactor case, pressure loads at the cavity walls are typically higher than that for the boiling water reactor case. This is because of the significantly larger boiling water reactor cavity, where the explosion pressure wave originating from the premixture in the center of the cavity has already been significantly weakened on reaching the distant cavity wall.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.6
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• pp.552-559
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• 2011

An interest in Arbitrary Lagrangian Eulerian (ALE) finite element methods has been increased due to more accurate responses in Fluid-Structure Interaction(FSI) problems. The multi-material ALE approach was applied to the prediction of the acceleration response of free-fall lifeboat, and its responses were compared to those of the single-material ALE one. It could be found that even though there was no big difference in the simulation responses of two methods, the single-material and multi-material ALE ones, the latter multi-material ALE method showed a little bit more close response to those of experimental results compared to the former single-material ALE one, especially in the x- and z-direction acceleration responses. Through this study, it could be found that several parameters in the ALE algorithms have to be examined more carefully for a good structural safety assessment of FSI problems.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.1
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• pp.1-20
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• 2013

In the present paper, the sloshing resistance performance of a huge-size LNG carrier's insulation system is evaluated by the fluid-structure interaction (FSI) analysis. To do this, the global-local analysis which is based on the arbitrary Lagrangian-Eulerian (ALE) method is adopted to accurately calculate the structural behavior induced by internal LNG sloshing of a KC-1 type LNG carrier insulation system. During the global analysis, the sloshing flow and hydrodynamic pressure of internal LNG are analyzed by postulating the flexible insulation system as a rigid body. In addition, during the local analysis, the local hydroelastic response of the LNG carrier insulation system is computed by solving the local hydroelastic model where the entire and flexible insulation system is adopted and the numerical analysis results of the global analysis such as initial and boundary conditions are implemented into the local finite element model. The proposed novel analysis techniques can potentially be used to evaluate the structural integrity of LNG carrier insulation systems.