• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.6
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• pp.850-858
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• 2002

The present study investigates in detail the combined effects of the Coriolis force and centrifugal force on the development of turbulent flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a curved region of U-bend, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal force due to the curvature of U-bend. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct. On the other hand, under negative rotation, where these two forces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces. Under the condition that the value of Rossby number and curvature ratio is large, the flow field in a rotating U-bend can be represented by two dimensionless parameters : $K_{TC}$ =Re $\sfrac{1}{4}$√λand a body force ratio F=λ/Ro. Here, $K_{TC}$ has the same dynamical meaning as $K_{TC}$ =Re√λ for laminar flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.531-538
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• 2013

The primary function of centrifugal compressor volute is to flow from the impeller and diffuser to the pipe system. The strength of the scroll vortex and flow pattern in the volute vary with the operating point. This is largely caused by the interaction between the impeller and the volute flow fields. The recirculation flow around the tongue and the scroll vortex can be used to understand the characteristics of the volute flow at off-design points. The present study aims to find the characteristics of a flow pattern in the diffuser and volute of a centrifugal compressor from the rectangular cross section of the volute. Measurements are carried out using PIV. The results obtained in this study show that the separation region around the tongue is reduced and that the recirculation flow increases as the flow coefficient decreases.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.159-169
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• 2002

The present study investigates in detail the combined effects of the Coriolis and centrifugal farce on the development of laminar flows in a square-sectioned U-bend rotating about an axis parallel to the center of bend curvature. When a viscous fluid flows through a rotating curved region, two types of secondary flow occur. One is caused by the Coriolis force due to the rotation of U-bend and the other by the centrifugal farce due to the curvature of U-bend. When the values of Rossby number and curvature ratio are large, the flow field in a rotating U-bend can be represented by two dimensionless parameters ; the Dean number K$\_$LC/=Re/√λ and a body ratio F=λ/Po. For positive rotation, where the rotation is in the same direction as that of the main flow, both the Coriolis force and the centrifugal force act radially outwards, the directions of the two secondary flows are the same. Therefore, the flow structure is qualitatively similar to that observed in a stationary curved duct with a larger f7c. On the other hand, in case of negative rotation, where two farces act in opposite direction, more complex flow fields can be observed depending on the relative magnitudes of the forces.

• Textile Coloration and Finishing
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• v.35 no.4
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• pp.239-245
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• 2023

Cellulose is an abundant biodegradable material in nature with excellent properties, but due to its poor processability, it has been widely studied for processing through modification. Cellulose acetate propionate (CAP) is a cellulose derivative in which the hydroxyl group of cellulose is replaced by acetyl and propionyl groups. CAP has several advantages, such as excellent solubility, structural stability, light and weather resistance, and good transparency. Porous nanofibers with excellent specific surface area, which can be applied in various fields, can be easily formed by the phase separation method using highly volatile solvents. High speed centrifugal spinning is a nano/micro fiber preparation method with advantages such as fast spinning and easy alignment control. In this study, a CAP/polybutylene succinate (PBS) spinning solution with chloroform as solvent was prepared to prepare porous microfibers and the fiber morphology was examined as a function of the disk rotation speed in an high speed centrifugal spinning device.

• Journal of the Korea Furniture Society
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• v.10 no.2
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• pp.63-71
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• 1999

본 연구는 목재중의 수분량이 변화하는 비정상태하에 있어서의 액체투과성을 평가하기 위한 새로운 방법으로써 원심법에 의한 액체투과성을 평가하기 위한 새로운 방법으로써 원심법에 의한 액체투과성의 평가법을 확립해 보고자 실시하였다. 이 방법은 원심력장에 있어서의 액체투과성과 원심처리부로부터 액체투과성을 평가하는 것이다. 실험결과, 삼나무(Cryptomeria japonica)와 미송 (Pseudotsuga menziesii)은 서로 다른 탈수경과를 나타내었다. 삼나무는 미송보다 더 많은 탈수량을 보였고 재내의 태수량의 변이가 심하였다. 한편 변재와 심재의 탈수거동에 있어서 삼나무는 기체투과성에 의해 평가된 값과 상반된 결과를 나타내었다. 즉, 2200∼3300rpm의 범위에서 편재는 심재보다 탈수량이 적었다.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.7
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• pp.921-929
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• 2011

We measured experimentally the properties of fluid dynamics, velocity fields, and the pressure, around stenotic obstruction located inside a circular channel structure. Particle image velocimetry system was employed to obtain velocity fields at the central section of the circular channel in the streamwise direction. The stenosis model used was made of acrylic material with different stenotic aspect ratios. The working fluid was water and it was returned by a centrifugal pump system. Pressure measurements were carried out to validate the effect of a narrow passageway. Results showed that the acceleration of gap flow through stenotic obstruction and the pressure drop in the recirculation regime behind the stenosis model can be observed.

• The KSFM Journal of Fluid Machinery
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• v.15 no.2
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• pp.45-50
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• 2012

The flow characteristics in a vaneless diffuser with a backswept radial impeller have been experimentally investigated according to the variation of discharge flow rate. Particle image velocimetry(PIV) system was applied to measure velocity fields with several operating conditions and on some diffuser horizontal planes. Pressure transducers were installed on hub wall of the diffuser in order to analyze the pressure fluctuations and their corresponding velocity fields. The results show that the location of the main flow center moves from the hub to the shroud side as the flow rate decreases, and the reverse flow is locally generated on the hub side.

• Korean Chemical Engineering Research
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• v.62 no.2
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• pp.181-190
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• 2024

Here, we develop a centrifugal microfluidic reactor with simple, fast, and high-throughput manner for the generation of magnetic Janus micro-adsorbents (MAs). By using the multi-micronozzle consisting of two separate aligned needles and centrifugal tubes, we have synthesized highly monodispersed Prussian blue- and magnetic nanoparticle-laden micro-adsorbents (PB-MNP-MAs). The enhanced cesium (Cs⁺) adsorption was demonstrated by conducting the adsorption isotherm and kinetics experiment which can be contributed to the porous nature of the Ca-alginate networks with a high surface area of embedded PB nanoparticles, resulting to perform rapid adsorption activity within 10 min. After Cs⁺ adsorption process, the as-synthesized PB-MNP-MAs were successfully harvested by introducing the external magnetic fields. Therefore, we believe that our findings can be provided new direction towards the development of advanced functional adsorbents in biological and environmental fields.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1065-1072
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• 2014

The shape of an impeller splitter for a dual-inlet centrifugal blower was optimized to enhance the blower performance. Two design variable, the normalized chord and pitch of a splitter, were used to evaluate the blower performance and internal flow fields based on the three-dimensional flow analysis. The blower performance obtained using this numerical simulation had a maximum error of 4 percent compared to that in an experiment at the design flow condition. The shape optimization of the splitter successfully increased the blower efficiency and pressure by 3.65 and 1.14 percent compared to the reference values. The blower performance was increased by reducing the flow separation near the blade suction surface by optimizing the shape of the splitter, which produced a pressure increase at the outlet of the volute casing.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.321-327
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• 2019

The purpose of this study is paper is to improve the flow performance and to reduce the aerodynamic noise of air discharge system consisting of a centrifugal fan, ducts and a housing for the clothes dryer. Using computational fluid dynamics and acoustic analogy based on FW-H (Ffowcs-Williams and Hawkings) Eq., air flow field and acoustic fields of the air discharge system are investigated. To optimize aerodynamic performance and aerodynamic noise, the response surface method is employed. The two factors central composite design using the inflow and outflow angles of fan blades is adopted. The devised optimum design shows the reduction of turbulent kinetic energy in the ducts and the housing of the system, and as a result, the improved flow rate and reduce noise is confirmed. Finally, the experment using the proto-type manufactured usign the optimum design shows the increase of flow rate by 4.2 %.