• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.29-35
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• 2000

The present numerical study investigates heat transfer enhancement mechanism for suspensions of polystyrene particles in water. Numerical simulations were done for turbulent hydrodynamic fully developed flows in a circular duct with constant wall heat flux. The experimental result of microparticle suspensions show 25∼45% heat transfer enhancement over those of water. The present numerical results show the main parameter for the heat transfer enhancement of microparticle suspension in a circular duct is the change of velocity profile by the non-Newtonian fluid behavior.

• Journal of ILASS-Korea
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• v.11 no.1
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• pp.7-16
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• 2006

Performance of thin films fabricated with the electrostatic spray deposition (ESD) technique is strongly governed by surface morphology, which depends on deposition parameters such as deposition time and temperature, solution properties, and surface characteristics of substrates. In this article, the state of the art on the relationships between the surface morphology and the deposition parameters is presented. Also studies on the electro-hydrodynamic atomization process and the motion of drops relevant to the ESD technique are briefly reviewed, and the future research works are suggested.

• Journal of Ship and Ocean Technology
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• v.4 no.1
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• pp.21-27
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• 2000

The slamming force occurring in the free fall impact of cylindrical bodies on the water surface is analyzed in both compressible and incompressible stages. In the compressible phase the hydrodynamic analysis is carried on by the acoustic approximation, obtaining a closed form expression for the maximum impact force. The incompressible analysis is approached through and unsteady boundary element method to compute the free surface evolution and the slamming force on the body. A similar behavior seems to characterize the maximum slamming force versus a dimensionless mass parameter.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.684-689
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• 2005

Parametric calculation were conducted to estimate performance of variable geometry of hydrogen recirculation blower for fuel cell vehicle. The pressure rise and efficiency are effected by change of the geometric parameter of impeller and casing, and stripper clearance under various mass flow. Hydrodynamic performance were evaluated, and also the inner flow fields were investigated by CFD. Calculated results show good coincidence with experimental test results of total pressure performance. Performance of model designed by parametric calculations satisfied experimental data of verification model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.271-276
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• 2006

This paper shows the rotordynamic characteristics of a turbo-generator for a BOP of a fuel cell system. The rotor-bearing system consists of magnetic shaft and compressor-turbine shaft, and the two shafts are connected by spline coupling and supported by oil free air foil bearing. Preliminary design according to several parameter is considered in detail. Static and dynamic characteristics of the AFB are estimated by the soft elasto-hydrodynamic analysis technique and the perturbation method. The results of the natural frequencies, mode shape, and unbalance response analysis are presented.

• Journal of The Korean Astronomical Society
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• v.34 no.4
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• pp.251-254
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• 2001

To examine the structure and dynamics of thick accretion disks, we use a two-dimensional viscous hydrodynamic code coupled with radiation transport. The $\alpha$-model and the full viscous stress-tensor description for the kinematic viscosity are used. The radiation transport is treated in the gray, flux-limited diffusion approximation. The finite difference methods used are based on an explicit-implicit method. We apply the numerical code to the Super-Eddington black-hole model for SS 433.@The result for a very small viscosity parameter a reproduces well the characteristic features of SS 433, such as the relativistic jets with $\~$0.26c, the small collimation degree of the jets, the mass-outflow rate of ${\ge}5{\times}10^{-7}M{\bigodot}yr^{-1}$, and the formation of the X-ray iron emission lines.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.190-196
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• 2005

The ratio between the hydrodynamic force produced by a submarine tau appendage and that acting on an equivalent appendage in isolation is regarded as tail plane efficiency. It is an important parameter in numerical simulations because it has a significant effect on predicted stability, controllability, and maneuverability. The paper introduces some recent work to improve the reliability and general applicability of current methods of tail plane efficiency estimation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.375-389
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• 2015

An improved boundary element method is presented for numerical analysis of hydrodynamic behavior of marine structures. A new algorithm for numerical solution of the finite depth free-surface Green function in three dimensions is developed based on multiple series representations. The whole range of the key parameter R/h is divided into four regions, within which different representation is used to achieve fast convergence. The well-known epsilon algorithm is also adopted to accelerate the convergence. The critical convergence criteria for each representation are investigated and provided. The proposed method is validated by several well-documented benchmark problems.

• Tribology and Lubricants
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• v.13 no.2
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• pp.89-95
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• 1997

This paper considers two dimensional analysis for lubrication between the single piston ring and the cylinder liner. The piston ring is treated as a reciprocating, hydrodynamic bearing with combined sliding and squeeze motion. Reynolds' equation is used, to model lubrication with Reynolds' cavitation boundary condition. This analysis is developed to get the cyclic variation of minimum film thickness and viscous frictional force. Two types of piston ring face shape are considered. This result can be used to study the influence of ring shape design parameter to improve the characteristics of sealing and lubrication.

• Journal of Ship and Ocean Technology
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• v.9 no.4
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• pp.11-22
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• 2005

This paper addresses details of wave load nonlinearity effect on stress RAO and damage ratio using component stochastic fatigue analysis. Traditional spectral fatigue analysis for ship structure is based on linear theory; however, there are a number of nonlinearity sources. Especially loading nonlinearity, such as hydrodynamic pressure applying to ship side and gravity changes due to roll and pitch motion, is thought to critically violate the linearity assumption of spectral fatigue analysis, which involves stress RAO as linear parameter. The main focus is placed on how to idealize complicated characteristics of loading nonlinearity and how to implement the nonlinear bias to linear spectral fatigue analysis.