• International Journal of Aeronautical and Space Sciences
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• v.18 no.1
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• pp.70-81
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• 2017

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multi-body dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.292-298
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• 1991

Previous studies on the performance of the round type impactor were reexamined and extended to the case of high particle mass loading. It was pointed out that the previous numerical studies need to be supplemented in the numerical process. The impactor performance was calculated under the same conditions as previous studies by the exact calculation process and it was found out that a tail of the collection efficiency curve, which have not been found in the previous studies, appeared in the results of ours. Numerical results for high particle mass loading show that the value of the collection efficiency in the impactor decreases but better particle-cut characteristics can be obtained, as the amount of the particle mass loading increases.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1366-1369
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• 2010

Along with the increasing need of sea development, the hydraulic stability of seabed structure on a soft seafloor ground is becoming an issue in the course of seaside development recently. However, the movement and hydraulic resistance or hydraulic stability of seafloor ground are mutually coupled with various phenomena, and there has been no clear proof for the issue, which makes it difficult to forecast. Furthermore, most researches are focused on hydraulic variables and the conditions of marine external force, while there have been few researches into the assessment in consideration of the type of a seafloor ground and the geotechnical characteristics. In addition, according to the periodic change of the flow direction, possible changes in hydraulic resistance performance of the seafloor deserves all the recognition. But there is no way to measure the hydraulic unstability of the sea ground due to tidal flow quantitatively. In this study, conventional hydraulic resistance measurement apparatus was improved to consider direction change of the current flow. Various artificial clayey soil specimens were made from Kaolinite and Jumunjin standard sand and hydraulic resistance tests were performed by changing the flow direction to validate the effect of the direction change on the scour of the seafloor.

• Journal of Ocean Engineering and Technology
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• v.27 no.5
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• pp.70-76
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• 2013

The present paper proposes a coupled volume-of-fluid (VOF) and level-set (LS) method for simulating incompressible two-phase flows that include surface tension effects. The interface of two fluids and its motion are represented by a VOF method designed using high-resolution differencing schemes. This hybrid method couples the VOF method with an LS distancing algorithm in an explicit way to improve the calculation of the normal and curvature of the interface. It is developed based on a rather simple algorithm to be efficient for various practical applications. The accuracy and convergence properties of the method are verified in a simulation of a single gas bubble rising in a three-dimensional flow with a large density ratio.

• Coupled systems mechanics
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• v.11 no.4
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• pp.315-333
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• 2022

Fluid-Structure Interaction (FSI) modeling is highly effective to reveal deformations, fatigue failures, and stresses on a solid domain caused by the fluid flow. Mechanical properties of the solid structures and the thermophysical properties of fluids can change under different operating conditions. In this study, we investigated the interaction of [45/-45]₂ wounded composite tubes with the fluid flows suddenly pressurized to 5 Bar, 10 Bar, and 15 Bar at the ambient temperatures of 24℃, 66℃, and 82℃, respectively. Numerical analyzes were performed under each temperature and pressure condition and the results were compared depending on the time in a period and along the length of the tube. The main purpose of this study is to present the effects of the variations in fluid characteristics by temperature and pressure on the structural response. The variation of the thermophysical properties of the fluid directly affects the deformation and stress in the material due to the Wall Shear Stress (WSS) generated by the fluid flow. The increase or decrease in WSS directly affected the deformations. Results show that the increase in deformation is more than 50% between 5 Bar and 10 Bar for the same operating condition and it is more than 100% between 5 Bar and 15 Bar by the increase in pressure, as expected in terms of the solid mechanics. In the case of the increase in the temperature of fluid and ambient, the WSS and Von Mises stress decrease while the slight increases of deformations take place on the tube. On the other hand, two-way FSI modeling is needed to observe the effects of hydraulic shock and developing flow on the structural response of composite tubes.

• Wind and Structures
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• v.23 no.6
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• pp.523-542
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• 2016

Snowdrift formation on roofs should be considered in snowy and windy areas to ensure the safety of buildings. Presently, the prediction of snowdrifts on roofs relies heavily on field measurements, wind tunnel tests and numerical simulations. In this paper, a new snowdrift modeling method by using CFD (Computational Fluid Dynamics) coupled with DEM (Discrete Element Method) is presented, including material parameters and particle size, collision parameters, particle numbers and input modes, boundary conditions of CFD, simulation time and inlet velocity, and coupling calculation process. Not only is the two-way coupling between wind and snow particles which includes the transient changes in snow surface topography, but also the cohesion and collision between snow particles are taken into account. The numerical method is applied to simulate the snowdrift on a typical stepped flat roof. The feasibility of using coupled CFD with DEM to study snowdrift is verified by comparing the simulation results with field measurement results on the snow depth distribution of the lower roof.

• Journal of Korea Water Resources Association
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• v.37 no.6
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• pp.509-515
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• 2004

In this study, comprehensive evaluation on the fully coupled SWAT-MODFLOW model is performed. Since combined model can consider the spatially varied daily recharge rate, groundwater modeling would be greatly enhanced. Also, combined model has been able to generate the distribution of groundwater heads with time, surface-subsurface flow modeling would be greatly advanced. River-aquifer interaction is well established in the combined model considering two-way interactions. Consequently, the reliability of groundwater discharge and total runoff of watershed would be greatly enhanced when combined model is used.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1463-1476
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• 2014

In order to understand hydrodynamic and morphodynamic characteristics under wave-current interactions in an estuary, a coupled model for two-way analysis between existing 3-d numerical wave tank and newly-developed 3-d morphodynamic model has been suggested. Comparing to existing experimental results it is revealed that computed results of the newly-suggested model are in good agreement with each laboratory test result for wave height distribution, vertical flow profile and topographical change around ocean floor pipeline in wave-current coexisting field. Also the numerical result for suspended sediment concentration is verified in comparison with experimental result in solitary wave field. Finally, it is shown that the 3-D coupled Hydro-Morphodynamic model suggested in this study is applicable to morphological change under wave-current interaction in an estuary.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2515-2518
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• 2008

The vacuum interrupter (VI) is widely used in medium-voltage switching circuits due to its abilities and advantages as an environmental friendly circuit breaker. An understanding of the vacuum arc flow phenomena is very important for improving the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and the thermal flow fields, simultaneously. In this study, we have investigated arc plasma constriction phenomena and an effect of AMF on the arc plasma with the high-current vacuum arcs for the cup-type AMF electrode by using a commercial finite element analysis (FEA) package, ANSYS. The simulation results applied with various AMFs and constant Joule heat generation show that strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. However, further studies are required on the two-way coupling method and radiation model for arc plasma in order to accomplish the advanced analysis method.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.417-423
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• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.