• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.06a
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• pp.107-114
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• 2000

Marine analysis was made to investigate the hydrodynamic effects of a Wing in Ground (WIG) by means of finite difference techniques. The air flow field around WIG is analyzed by the Marker & Cell (MAC) based method, and the interaction between WIG and the free surface are studied by showing pressure distributions above the free surface. In the latter part, computations are extended to make clear the flow characteristics of a high speed catamaran in the rang of Froude numbers 0.2 to 1.0 with a separation to length ratios of 0.2, 0.3 and 0.5. The Navier-Stokes solver is invoked in which the nonlinear free-surface boundary condition is applied. For the validation, computational results are compared with the experiments.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.29-34
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• 2000

This paper describes a numerical study to make clear the characteristics of flow around a high speed catamaran hull advancing on calm water. The simulation is carried out at Froude number of 0.5 with a separation to length rations of 0.2 to 0.5. To simulate the flows, the Navier-Stokes solver is employed in which the free surface condition is included. Computations are performed in a rectangular grid system based grid system based on the Marker & Cell method. For the validation, the computation results are compared with the experiments.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.223-226
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• 2006

Computational Study of a sphere subjected to free stream flow and simultaneously subjected to spinning motion is carried out. Three dimensional compressible Navier-Stokes equations are solved using fully implicit finite volume scheme. SST(Shear Stress Transport) $k-{\omega}$ turbulence model is used. Aerodynamic characteristics being affected are studied. Validation of the numerical process is done for the no spin condition. Variation of drag coefficient and shock wave strength with increase in spinning rate is reported. Changes in the wake region of the sphere with respect to spinning speed are also observed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.1
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• pp.90-94
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• 2004

Generally, a hydraulic cylinder block which is one of a vehicle parts that plays Important role in excavator power transmission, has copper alloy separation phenomenon by sliding motion between metals in high pressure condition. In this paper, to solve this problem, the interfacial reaction layer of Fe-Cu With SCM440 and copper alloy is studied through the melting method. As the result of this study, it is found that the interfacial reaction layer of $1{\mu}m$ created in the interface of Fe-Cu which has very strong physical bonding. It has been also confirmed that the melting method can improve life of the hydraulic cylinder block.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.329-336
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• 2009

A fretting wear test rig for cross contacting tube specimens, which employs a piezoelectric actuator, has been developed. Along with the simple loading scheme using dead weights, the rig is very simple to be used also. The accuracy was found acceptable. Inconel 690 tubes were tested in room temperature and ambient condition. Normal load and sliding amplitude range up to 35N and $100{\mu}m$, respectively. The sizes of wear scar and the wear volumes were measured, and wear coefficients have been calculated based on those. A study on the fretting wear mechanism of the tubes has been attempted via microscopic observation. Rugged wear surfaces are induced by the separation and adhesion of particles and formation and subsequent fracture of surface layers. Lapped specimens were also tested and abrasive wear seems to be playing a dominant role.

• 한국가시화정보학회:학술대회논문집
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• 2007.11a
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• pp.59-62
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• 2007

The basic concept and preliminary performance results of a miniaturized electroosmotic (EO) pump with diaphragms were included in the present study. The separation of an electroosmotic pumping liquid from a drug using diaphragms is mainly to have a freedom in choosing an electroosmotic pumping liquid and to achieve the optimal drug delivery, and, preferably its precise control. We performed maximum flow rate, maximum pressure, and maximum current measurements with and without diaphragm designs. As a result, the effect of diaphragms on pump performance at the maximum condition is small. However, the presence of diaphragms does not allow indefinite continuous pumping.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.181-184
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• 2002

CFD calculations are carried out to investigate the turbulent flow characteristics inside the duct of marine waterjet propulsors. The Reynolds-averaged Wavier-Stokes equations are solved using a finite-volume method. Standard $k-{\varepsilon}$ model and realizable $k-{\varepsilon}$ model are evaluated with an existing experimental data. Multi-block grid topology is adopted to describe the details of complex duct geometry. The present numerical methods are applied to the preliminary duct design of new waterjet propulsor system. Four different influx conditions are simulated to find out pressure and velocity distribution inside the intake duct. Attention is also paid upon the possible flow separation inside the waterjet duct. It is found that CFD tools can be used for the initial evaluation of inflow condition into the impeller of waterjet propulsor system.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.269-270
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• 2006

A finite difference lattice Boltzmann model which allows us to simulate gas-liquid two-phase flows with large density difference, for instance, 800 times for air and water is considered. Two-particle model is used and the density difference is introduced by changing the acceleration according to the fluid density. Numerical measurement of surface tension agrees well with theoretical predictions. Simulations of two-phase phenomenon for phase-transition is carried out, showing applicability of the model for two-phase flows. The two-dimensional cavitating flow around a board set up in the fluid way is also simulated. As a result, it was confirmed that the FDLB method with two-particle model was effective in numerical simulation of cavitating flow and the bubble periodically grew up at the low pressure area behind the board, in which the fluid condition was influenced by the cavitation number.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.368-373
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• 2001

A major concern on high-energy centrifugal pump is the potential for interaction of two-phase flow phenomena with mechanical response of the pumping elements. The other concern is the pressure pulsations created from trailing edge of the impeller blade and flow separation and recirculation at partial load in centrifugal pumps. These interactions generating between rotor and casing cause dynamic pulsation on pump and exciting pipeline vibration. The higher severity responses, the more lead to failure of pump and system components. Finally, it cause severe axial vibration of single stage pump due to the hydraulic instability in flow condition below BEP.

• Asian Journal of Turfgrass Science
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• v.12 no.4
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• pp.195-202
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• 1998

The development of a protocol for high efficiency of embryogenic callus separation, maintenance and plant regeneration from the seeds of zoysiagrass cv. Zenith was studied. Embryogenic callus ratio is absolutely determined by genotype, but by adding high concentration of copper into medium, changing light condition and maintaining callus on initial induction medium for 8∼10 weeks, embryogenic callus can be easily distinguished and its growth can be promoted. There were significant differences among selected callus lines (each from one seed) according to their growth rates and regeneration percentages. Callus pre-treatment with activated charcoal inhibited callus growth, increased the level of precocious germination during culture and promoted shoot cluster formation after transfer to regeneration medium. For long-term callus maintenance, N6AA medium was better than MS medium, because the former inhibited non-embryogenic callus formation and kept vigor of embryogenic callus. The best callus lines Z-(5) has been successfully used for transformation and somaclonal variation selection in our laboratory.