• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.50-52
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• 2007

In the present paper, some difficulties encountered in predicting airfoil characteristics are described and solutions for those problems are discussed Since drag is determined by the amounts of pressure and, especially, shear stress, accurate estimation of shear stress is very crucial. However shear stress computation is dependent on the grid density and turbulence model, it should be consistent in preparing grid and turbulence model. When the transition from laminar to turbulent happen at the middle of airfoil, CFD solver should divide the region into laminar and turbulent region based on the transition location.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.04a
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• pp.19-22
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• 2009

It is essential to predict the deformed roll profile for the prediction of the strip profile in rolling process. The work roll of the Sendzimir mill has a small diameter in comparison to a barrel length, so that it is well deformed by the rolling pressure. Also it has a complex roll system, so it is difficult to analyze the roll deflection. In this paper, 3D finite element method is used for the analysis of the roll deflection of the Sendzimir due to the contact between rolls. But it takes much time to get the results, so that the on-line model to evaluate the radial deformation of a roll is developed on the basis of the finite element method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.22-24
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• 2008

This paper presents a numerical model of internal flows in a lubricant supplying and scavenging flow path of an aero-engine lubrication system. The numerical model was built in the General Analysis Software of Aero-engine Lubrication System, GASLS, developed by Northwestern Polytechnical University. The lubricant flow flux, pressure and temperature distribution at steady state were calculated. GASLS is a general purpose computer program employed a 1-D steady state network algorithm for analyzing flowrates, pressures and temperatures in a complex flow network. All kinds of aero-engine lubrication systems can be divided into finite correlative typical elements and nodes from which the calculation network be developed in GASLS. Special emphasis is on how to use combined elements which is a type of typical elements to replace some complex components like bearing bores, accessory gearboxes or heat exchangers. This method can reduce network complexity and improve calculation efficiency. Final computational results show good agreement with experimental data.

• Geomechanics and Engineering
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• v.38 no.5
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• pp.467-476
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• 2024

This study investigates Tunnel Boring Machine (TBM) performance prediction by employing discrete event simulation technique, which is a potential remedy highlighting its stochastic adaptability to the complex nature of TBM tunnelling activities. The new discrete event simulation model using AnyLogic software was developed and validated by comparing its results with actual performance data for Daegok-Sosa railway project that Earth Pressure Balance (EPB) TBM machine was used in Korea. The results showed the successful implementation of predicting TBM performance. However, it necessitates high-quality database establishment including geological formations, machine specifications, and operation settings. Additionally, this paper introduces a novel methodology for daily performance updates during construction, using automated data processing techniques. This approach enables daily updates and predictions for the ongoing projects, offering valuable insights for construction management. Overall, this study underlines the potential of discrete event simulation in predicting TBM performance, its applicability to other tunneling projects, and the importance of continual database expansion for future model enhancements.

• Tribology and Lubricants
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• v.27 no.4
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• pp.218-223
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• 2011

To improve the performance of a bent-axis type axial piston pump driven by the tapered pistons, it is necessary to know the pressure ripple characteristics. The purpose of this paper is to understand the effect on the pressure ripple characteristics and the prediction by comparing experimental and theoretical results. The simulation model of the bent-axis type axial piston pump is developed in the AMESim environment using the geometrical dimension and the driving mechanism of the piston pump. The results can be obtained to predict the performance characteristics of the bent-axis type axial piston pump.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.930-936
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• 2008

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

• The Journal of the Acoustical Society of Korea
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• v.2 no.1
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• pp.48-58
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• 1983

The transient sound radiation from the impact between a steel ball and a thick plate is analyzed theoretically and compared with experiment results. The derivation process itself is difficult to analyze sound radiation characteristics theoretically for a thick plate with some resonances but may be investigated from measured data. During mechanical impacts, arbitrary driving point importance for an elastic system enables to predict by using mechanical importance method. In order to obtain approximate solution for an impact model testing, the surface Helmholtz integral formulation based on the integral expression for pressure in the field in terms of surface pressure and normal velocity is used as a basis. A simple expression is developed for an impulsive response function, which is time dependent velocity potential and pressure for an impact may then be computed by a convolution of exciting force. In estimating of elastic-acoustical correlation problems, mechanical inertance, overall transfer function and radiation resistance obtained by signal processing techniques are used. The usefulness is confirmed by applying these methods prediction of arbitray driving pint inertance, radiated sound pressure and exciting force.

• Fire Science and Engineering
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• v.33 no.5
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• pp.48-54
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• 2019

A Large Eddy Simulation (LES), adopting the Eddy Dissipation Concept (EDC) 1-step model, was successfully performed for backdraft phenomena. The activation energy of the finite chemistry reaction in the EDC 1-step model was adjusted to simulate the backdraft. The prediction of the EDC 1-step model was similar to that of the Mixing-Controlled Fast Chemistry (MCFC) model, except when the backdraft occurred. The EDC 1-step model could be used to simulate the experimental peak pressure, but not the first peak pressure of the backdraft.

• Journal of the Korean GEO-environmental Society
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• v.18 no.11
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• pp.27-33
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• 2017

Nonlinear dynamic analysis is performed to calculate the response of U-shaped cantilever retaining structure under seismic loading using the finite element (FE) analysis program OpenSees. A particular interest of the study is to evaluate whether the moment demand in the cantilever can be accurately predicted, because it is an important component in the seismic design. The numerical model is validated against a centrifuge test that was performed on cantilever walls with dry medium dense sand in backfill. Seismic analysis is performed using the pressure-dependent, multi-yield-surface, plasticity based soil constitutive model implemented in OpenSees. Normal springs are used to simulate the soil-structure interface. Comparison with centrifuge show that FE analysis provides good estimates of both the acceleration response and bending moment. The lateral earth pressure near the bottom of the wall is overestimated in the numerical model, but this does not contribute to a higher prediction of the moment.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.47-53
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• 2005

This paper presents the effects of ambient pressure on atomization characteristics of high-Pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. In order to investigate the atomization process numerically, the LISA-DDB hybrid model was utilized. This breakup model assumes that the primary breakup occurs when the amplitude of the unstable waves is equal to the radius of the ligament of liquid sheet near the nozzle and the droplet deformation induces the secondary breakup. The results provide the effect of ambient pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is also revealed that the accuracy of prediction of LISA-DDB hybrid model is pretty good in terms of spray developing process, spray tip penetration, and SMD distribution.