• 한국초전도학회:학술대회논문집
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• v.14
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• pp.37-37
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• 2004

• 한국초전도학회:학술대회논문집
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• v.14
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• pp.42-42
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• 2004

• Proceedings of the Korean Magnestics Society Conference
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• 2007.12a
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• pp.186-187
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• 2007

• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.139.2-139.2
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• 2008

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.45-45
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• 2011

• Proceedings of the Korean Magnestics Society Conference
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• 2011.06a
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• pp.24-24
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• 2011

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.9
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• pp.731-737
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• 2014

A vortex chamber is a simple device that separates compressed gas into a high-temperature stream and a low-temperature stream. It is increasing in popularity as a next-generation heat exchanger, but the flow physics associated with it is not yet well understood. In the present study, both experimental and numerical analyses were performed to investigate the temperature separation phenomenon inside the vortex chamber. Static pressures and temperatures were measured using high-sensitivity pressure transducers and thermocouples, respectively. Computational fluid dynamics was applied to simulate 3D unsteady compressible flows. The simulation results showed that the temperature separation is strongly dependent on the diameter of the vortex chamber and the supply pressure at the inlet ports, where the latter is closely related to the viscous work. The previous concept of a pressure gradient wave may not be a reasoning for temperature separation phenomenon inside the vortex chamber.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.396-403
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• 2018

In this paper, a high-performance and low-noise centrifugal fan is developed for cooling automotive seats which provide a driver with pleasant driving environment. First, the flow characteristics of the existing fan unit was analyzed using a fan performance tester and CFD (Computational Fluid Dynamics) simulations. The analysis of the predicted flow field indicated vortex flow near the tip of fan hub and stagnation flow on the top of fan hub. Two design points are devised to reduce the vortex flow and the stagnation flow observed in the existing fan unit. First, the cut-off clearance which is the minimum distance between the fan blade and the fan housing is increased to reduce the vortex strength and, as a result, to reduce the overall sound pressure level. Second, the hub shape is more modified to eliminate the stagnation flow. The validity of proposed design is confirmed through the numerical analysis. Finally, a prototype is manufactured with a basis on the numerical analysis result and its improved flow and noise performances are confirmed through the P-Q curves measured by using the Fan Tester and the SPL (Sound Pressure Level) levels measured in the anechoic chamber.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.473-478
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• 2003

Numerical study was made on the flow characteristics around a circular pipeline between parallel walls. The incompressible Navier-Stokes equations were solved by using a third-order upwind differential scheme. When the distance near a wall is small enough, the vortex shedding is almost completely suppressed because of the interaction with the wall boundary layer separation. This study aims to clarify the characteristics of the vortex shedding regime as the body approaches a wall as Reynolds number varies. The feature of separated vorticity dynamics is analyzed at different conditions with particular attention to the interaction between the pipeline wake and the induced separation on the plane walls.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.3
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• pp.219-227
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• 2016

Numerical simulation based on the Reynolds Averaged Naviere-Stokes (RANS) Computational Fluid Dynamics (CFD) method had been carried out with the commercial code ANSYS CFX. The structured grid and SST $k-{\omega}$ turbulence model had been adopted. The impact of non-condensable gas (NCG) on cavitation performance had been introduced into the Schnerr and Sauer cavitation model. The numerical investigation of cavitating flow of marine propeller E779A was carried out with different advance ratios and cavitation numbers to verify the numerical simulation method. Tip clearance effects on the performance of pumpjet propulsor had been investigated. Results showed that the structure and characteristics of the tip leakage vortex and the efficiency of the propulsor dropped more sharply with the increase of the tip clearance size. Furthermore, the numerical simulation of tip clearance cavitation of pumpjet propulsor had been presented with different rotational speed and tip clearance size. The mechanism of tip clearance cavitation causing a further loss of the efficiency had been studied. The influence of rotational speed and tip clearance size on tip clearance cavitation had been investigated.