• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.703-714
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• 2010

This paper describes the design optimization of a rotating rectangular channel with staggered arrays of pin-fins by Kriging metamodeling technique. Two non-dimensional variables, the ratio of the height to the diameter of the pin-fins and the ratio of the spacing between the pin-fins to the diameter of the pin-fins are chosen as the design variables. The objective function that is a linear combination of heat transfer and friction loss related terms with a weighting factor is selected for the optimization. To construct the Kriging model, objective function values at 20 training points generated by Latin hypercube sampling are evaluated by a three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis method with the SST turbulence model. The Kriging model predicts the objective function value that agrees well with the value calculated by the RANS analysis at the optimum point. The objective function is reduced by 11% by the optimization of the channel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5412-5419
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• 2011

The need is growing for high-speed spindle because various equipment are becoming more precise, miniaturization and high speed with the development of industries. Air-lubricated dynamic bearings are widely used in the optical lithographic manufacturing of wafers to realize nearly zero friction for the motion of the stage. Air-lubricated dynamic bearing can be used in high-speed, high-precision spindle system and hard disk drive(HDD) because of its advantages such as low frictional loss, low heat generation, averaging effect leading better running accuracy. In the paper, numerical analysis is undertaken to calculate the performance of air-lubricated dynamic bearing with herringbone groove. The static performances of herringbone groove bearings which can be used to support the thrust load are calculated. Electrochemical micro machining($EC{\mu}M$) which is non-contact ultra precision machining method has been developed to fabricate the air-lubricated dynamic bearing and optimum parameters which are inter electrode gap size, concentration of electrolyte, machining time are simulated using numerical analysis program.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.71-71
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• 2018

Sea pollution accidents have been occurred due to the increase of marine ship traffic. Oil spill from the hull hole induced by tanker collision results in the huge sea pollution. Proper and prompt reaction on such oil spill disaster is needed to minimize the damage. Thru-hull emergency wood plug is typically used to manually close small holes, while it is required to develop some mechanical devices for closing large holes in the hull due to huge fluid pressure. Accurate estimation of oil discharge and velocity from such holes are important to develop proper device to control hull hole damage. High resolution CFD modeling investigation on the configurations of hull hole of 7.5 m initial depth and 30 cm diameter, which was observed in the oil spill accident of the Hebei Sprit off the west coast of Korea in 2007, has been carried out to compute the oil spill velocity distribution in terms of flow depth. Friction loss due to the viscous flow and the discharge coefficient of crude oil with specific gravity SG = 0.85 and viscosity of $4-12cP(mPa{\cdot}s)$ at the temperature of $20^{\circ}C-100^{\circ}C$ are presented in terms of Reynolds number based on the results of high-resolution CFD modeling.

• Journal of Biosystems Engineering
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• v.7 no.2
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• pp.30-35
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• 1983

To investigate the factors affecting the transportability of spray droplets, the maximum distance, the effective distance, the ratio of even distribution, and the diameters of particles were measured in accordance with the different pressure levels of power sprayer using 3 hole swath type nozzle, and the results are summerized as follows; 1. The distance of the most dense point from the nozzle was shortened by 0.5 meter with the 100-meter-long hose. The maximum reaching distances were reduced by 1.5 and 1.0 meters for the 13m/m and the 8.5 m/m hoses respectively, and the effective distance were reduced by 0.5 meter for both cases. 2. The effective distance can not be extended beyond 14 meters even if the length of hose is minimized at the rated pump pressure 28 kg/$cm^2$, it was 1 meter longer for 13m/m hose compared to the 8.5m/m one. 3. In case of 13m/m hose, the most dense point can be extended further by 0.5 meter increasing the pump pressure by 8 kg/$cm^2$, and the maximum distance and effective distance were increased by 2.0 and 0.5 meters respectively. There was no significant effect of pressure changes on the transportability in case of 8.5m/m hose. 4. Both the reduction of hose length and the increase of pump pressure influenced in large extent to the atomization effect of droplets. It was noticed that the diameter of droplet is related to the pump pressure and inside diameter of hose. 5. The pressure drop in 100-meter-long and l3m/m hose was 5~7kg/$cm^2$ at the pump pressure range of 25~33kg/$cm^2$, and it is an equivalent of 2% per 10 meter length of hose.