• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.4
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• pp.225-227
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• 2012

This paper presents a chemical etching system for groove manufacturing for the fluid and aero dynamic bearings. To manufacture the grooves to thrust and journal surface of the fluid and aero dynamic bearing, it is very important for grooves' depth to be smaller tolerance. It is very difficult for the internal surface of journal bearing to make the grooves precise. If the precision of the groove is not exact, we can not get the desirable performance for the target of the dynamic bearing. To make the groove of bearing precise, we propose the method of chemical etching system. It has known that the method of chemical etching can not make the groove on the internal surface of journal bearing excepts for on the surface of thrust bearing. However, this paper has shown the solution to make the grooves on it. We obtain the condition and the parameters of the system such as time, chemical material composition and so on. In this paper, we get the experimental results to verify the precise groove manufacturing for the fluid and aero dynamic bearing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.90-94
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• 1996

Thermal problems of creep-feed grinding are more serious than regular grinding. So grinding fluid supply in creep-feed grinding is very important. Grinding fluid supply quantity is not linear with effectiveness because grinding wheel is porosity material and the grinding area is solid contact area. In this paper, by using AE signal, optimal quantity of fluid supply was determined. And surface characteristics of wet creep-feed grinding were analized.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.46-50
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• 2018

The purpose of this study is to analyze effects of filtering system of cutting fluid which is used for machining silicon electrode. For the research, different sizes of filter clothes are applied to check grain size of sludge of cutting fluid. Surface roughness of machined workpiece, depth of damage inside of silicon electrode, and suspended solids of cutting fluid are experimented and analyzed. From these experiments, it is verified that filtering system of cutting fluid is very important factor for machining. Results of this study can affect various benefits to the semiconductor industry for better productivity and better atmospheric pollution in workplace.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.59-64
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• 2008

Micro machining can manufacture complex shapes with high accuracy. Especially, this enables wide application of micro technology in various fields. For example, micro channels allow fluid transfer, which is a widely used technology. Therefore, liquidity research of flow in micro channels and micro channel manufacturing with use of various materials and cutting conditions has very important meaning. In this study, to find out correlation between fluid velocity in micro channels and surface roughness, we manufactured micro channels using micro end-mill and dropped ethanol into micro channels. We compared several surface roughness and fluid velocity in micro channels that were created by various processing conditions. Finally, we found out relationship between fluid velocity and surface roughness in micro channels of different materials.

• Journal of Drive and Control
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• v.13 no.1
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• pp.27-33
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• 2016

In hydraulic machinery, the hydraulic fluid acts primarily as working fluid and secondarily as a lubricant. Hence, the viscous friction force acting on the sliding components should be reduced to improve the mechanical efficiency. It is now well known that the surface texturing is a useful method for friction reduction. In this study, using a commercial computational fluid dynamics (CFD) code, FLUENT, the lubrication characteristics of a surface textured slider bearing under high boundary pressure difference is studied. The streamlines, velocity profiles, pressure distributions, load capacity, friction force and leakage flowrate are highly affected by the film thickness ratio and the textured region. Partial texturing at the inlet region of the inclined slider bearing can reduce both friction force and leakage flowrate than in the untextured case. The present results can be used to improve the lubrication characteristics of hydraulic machinery.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.1-1
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• 2009

In this presentation, I talk about various fluid simulation methods that have been developed for computer graphics special effects since 1996. They are all based on CFD but sacrifice physical reality for visual plausability and time. But as the speed of computer increases rapidly and the capability of GPU (graphics processing unit) improves, methods for more physical realism have been tried. In this talk, I will focus on four aspects of fluid simulation methods for computer graphics: (1) particle level-set methods, (2) particle-based simulation, (3) methods for exact satisfaction of incompressibility constraint, and (4) GPU-based simulation. (1) Particle level-set methods evolve the surface of fluid by means of the zero-level set and a band of massless marker particles on both sides of it. The evolution of the zero-level set captures the surface in an approximate manner and the evolution of marker particles captures the fine details of the surface, and the zero-level set is modified based on the particle positions in each step of evolution. (2) Recently the particle-based Lagrangian approach to fluid simulation gains some popularity, because it automatically respects mass conservation and the difficulty of tracking the surface geometry has been somewhat addressed. (3) Until recently fluid simulation algorithm was dominated by approximate fractional step methods. They split the Navier-Stoke equation into two, so that the first one solves the equation without considering the incompressibility constraint and the second finds the pressure which satisfies the constraint. In this approach, the first step introduces error inevitably, producing numerical diffusion in solution. But recently exact fractional step methods without error have been developed by fluid mechanics scholars), and another method was introduced which satisfies the incompressibility constraint by formulating fluid in terms of vorticity field rather than velocity field (by computer graphics scholars). (4) Finally, I want to mention GPU implementation of fluid simulation, which takes advantage of the fact that discrete fluid equations can be solved in parallel.

• Tribology and Lubricants
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• v.26 no.4
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• pp.230-239
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• 2010

Mechanical face seal installed in boiler feedwater pump prevents leakage of working fluid using thin fluid film between stator and rotor. If the leakage of working fluid exceeds the allowable volume, serious malfunction of boiler feedwater pump will be happen. The thinner fluid film exists between stator and rotor, the less working fluid leaks out. However, if the thickness of fluid film is not enough, the wear of seal face will be increased. And it causes the decrease in life of mechanical face seal. Therefore appropriate design is necessary to maximize the performance and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to investigate the static characteristics of wavy mechanical face seals which have 4 different wavy surface profiles on rotor. As a result, opening force, leakage volume of working fluid and friction torque were obtained. For the same minimum film thickness, the static characteristics of mechanical face seal were affected by the wavy surface profile which can change the thickness of working fluid film and pressure distribution.

• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.44-50
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• 2011

In this study, we propose a method for characterizing fluid-mechanical properties of a fluid surface, such as surface dilatational and shear viscosity, by matching the flow visualization and the numerical simulation for a Stokes flow in a three-dimensional cavity. The surface flow is driven by shear stress exerted on the free surface by an external gas flow. The external gas flow is simulated by using a commercial code, while the Stokes flow is calculated by an in-house code. We have found that the surface flow is very sensitive to the surface tension and other properties. The qualitative feature of the surface flow can be reproduced by the parameter tuning.

• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.9-10
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• 2006

A numerical method for simulating tree surface flows including the surface tension is presented. Numerical scheme is based an a fractional-step method with a finite volume formulation and the interface between liquid and gas is tracked by Volume of Fluid (VOF) method. Piecewise Linear Interface Calculation (PLIC) method is used to reconstruct the interface and the surface tension is considered using a Continuum Surface Force (CSF) model. Several free surface flow phenomena were simulated to show its effectiveness to find such phenomena.

• Tribology and Lubricants
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• v.28 no.2
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• pp.70-80
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• 2012

Non-contact type mechanical face seals installed in mechanical systems prevent leakage of working fluid using thin working fluid film between stator and rotor. For that purpose, various kinds of surface profiles, grooves and conings have been applied on seal surfaces of stator and rotor to generate hydrodynamic and hydrostatic pressure. The thickness distribution of working fluid film is one of important factors which affect the working performances of mechanical face seal, and it is strongly affected by the surface height profiles of stator and rotor. Therefore, appropriate design of surface height profiles of stator and rotor is necessary to optimize the working performances and life of mechanical face seal. In this study, numerical analysis using finite volume method was conducted to estimate the working performances of wavy mechanical face seals which have 36 coning combinations. As results, minimum thickness of working fluid film, leakage volume of working fluid and friction torque in static equilibrium condition of mechanical face seal, and stiffness of working fluid film were obtained. The results show that the working performances of mechanical face seal were affected by the coning combinations which can change the thickness distribution of working fluid film and pressure distribution in sealing region of mechanical face seal.