• Proceedings of the KSME Conference
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• 2004.11a
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• pp.302-307
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• 2004

The major flow-induced vibration mechanisms such as fluid-elastic and turbulence excitation can cause the various types of wear of the steam generator tubes in unclear power plant. It is generally accepted that the tube wear due to vibration is affected by the presence of gap clearance between tube and support plate. Connors showed that the tube wear depth could be estimated by using the relationship between wear volume and sliding distance for contact time. Au-Yang predicted the wear depth by using the nonlinear characteristics of normal work rate to contact time. In this study the effect of gap size on the steam generator tubes wear is analyzed by deriving the wear depth versus normal work rate relationship from these previous results.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.215-222
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• 1996

This paper reports on theoretical study of the compression process within balanced type vane pump for Electro-Hydraulic Power Steering(EHPS). Equations fo camring profiles are derived, then displacements, velocities, accelerations, and jerks are calculated. Vane side leakages, vane slit leakages, and rotor side leakages are considered and calculated. Numerical integration of flow equation is performed using 4th Runge-Kutta method. As a result of analysis, it is found that chamber pressure depends on rotational speeds, bulk modulus of fluid, notches, camring profiles, and positions of delivery port. Especially, the variation of notch area is the most important factor that prevents pressure from rapid rising.

• Tribology and Lubricants
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• v.26 no.4
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• pp.219-223
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• 2010

Despite the increasing need of nanometer-scale accuracy in abrasive machining using ultrasmall particles such as abrasive jet and chemical mechanical polishing(CMP), the process mechanism is still unknown. Based on the background, research on the effects of various process parameters on the machined surface at abrasive machining was motivated and performed by using finite element analysis where the effect of slurry fluid flow involved. The effect of particle shape on the machined surface during particle-surface collision was discussed in this paper. The results from FEA simulation revealed that any damage or defect generation on machined surface by the impact may occur only if the particle has enough impact energy. Therefore, it could be concluded that generation of the defects and damage on the wafer surface after CMP process was mainly due to direct contact of the 3 bodies, i.e., pad-particle-wafer.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.10a
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• pp.429-436
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• 1995

This paper describes a methodology for determination of representative CANDU feeder geometry and the pressure drops between inlet/outlet header and fuel channel in the primary loop. A code, MEDOC, was developed based on this methodology and helps perform a calculation of equivalent feeder geometry for a selected channel group on the basis of feeder geometry data (fluid volume, mass flow rate, loss factor) and given property data pressure, quality, density) at inlet/outlet header. The equivalent feeder geometry calculated based on this methodology will be useful fur the transient thermohydraulic analysis of the primary heat transport system for the CANDU heavy water-cooled pressure tube reactor.

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.11-18
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• 1998

The present experimental study is focused on the application of multi-point simultaneous measurement by PIV(Particle Image Velocimetry) to rotor-stator region within centrifugal turbine pump. Six different kinds of rpm(120, 500, 1000, 1500, 2000 and 2500) are selected as experimental condition. Optimized cross correlation identification to obtain velocity vectors is implemented by direct calculation of correlation coefficients. Fine optical setup deeply concerned with PIV performance is arranged for accurate PIV measurement of high-speed complex flow. The instantaneous and time-mean velocity distribution and velocity profile are represented quantitatively at the rotor and stator region.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.96-104
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• 1996

Hamilton's principle is used to derive Euler-Lagrange equations for free surface flow problems of incompressible ideal fluid. The velocity field is chosen to satisfy the continuity equation a priori. This approach results in a hierarchial set of governing equations consist of two evolution equations with respect to two canonical variables and corresponding boundary value problems. The free surface elevation and the Lagrange's multiplier are the canonical variables in Hamilton's sense. This Lagrange's multiplier is a velocity potential defined on the free surface. Energy is conserved as a consequence of the Hamiltonian structure. These equations can be applied to waves in water of finite depth including generalization of Hamilton's equations given by Miles and Salmon.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.78-83
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• 2010

Since a tower crane is too high for a worker to ascend and by the wind in the high altitude, the possibility of a safety accident is very high, a lift assist is used. In this study, the hydraulic fall prevention device using the pressure generation device by Seok, et al. was developed. For this, the effects on the fall prevention performances of factors such as gear clearance, oil viscosity, rotative velocity and so on were evaluated by the analysis of fluid flow using FEM and the prototype was producted and a function test was performed.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.163.2-163.2
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• 2011

Due to global warming, the need to secure an alternative resource has become more important nationally. Due to the high tidal range of up to 9.7m on the west coast of Korea, numerous tidal current projects are being planned and constructed. To extract a significant quantity of power, a tidal current farm with a multi-arrangement is necessary in the ocean. The rotor, which initially converts the energy, is a very important component because it affects the efficiency of the entire system, and its performance is determined by various design variables. The power generation is strongly dependent on the size of the rotor and the incoming flow velocity. However, the interactions between devices also contribute significantly to the total power capacity. Therefore, rotor performance considering the interaction problems needs to be investigated for generating maximum power in a specific field. This paper documents the characteristics of wake induced by horizontal axis tidal current power turbine.

• Tribology and Lubricants
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• v.16 no.2
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• pp.106-113
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• 2000

Effects of surface roughness on bearing performances are investigated numerically in this study, especially for the parallel thrust bearing. Although mating surfaces are parallel and separated by thin fluid film, the pressure distribution is formed due to asperities. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation is applied to predict the effects of surface roughness between hydrodynamic and mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness. The correlation length is proposed to get the minimum load for the parallel thrust bearing for various sliding conditions.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.1
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• pp.22-28
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• 2008

Generally block imbedded type oil pump is adopted to make a small engine. In this paper 1D/3D numerical simulations were conducted to reduce energy consumption of the block imbedded type oil pump. At each stage of engine development we have estimated the oil flow rate and pressure to optimize oil pump sizes by using the 1D system analysis and then accomplished 3D CFD(Computational Fluid Dynamics) simulations to optimize oil pump shapes including inlet/outlet port. As a result, the energy consumption of oil pump has been reduced to nearly 27% and the engine fuel consumption to $1{\sim}1.5%$.