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RISS 인기검색어
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- 저자 : 허정기(Jeong-Ki Huh) (검색결과 3 건)
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마이크로 리블렛이 부착된 NACA 0012 익형 후류의 PIV 속도장 측정 연구
허정기(Jeong Ki Huh),이승섭(Seung Seob Lee),이상준(Sang Joon Lee) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
Riblets with grooves along the streamwise direction have been known as an effective passive control technique for drag reduction. The near wake behind a NACA 0012 airfoil on which a flexible micro-riblet surface is attached has been investigated experimentally for the drag decreasing (U? = 3.3 ㎧) and drag increasing (U? = 7 ㎧) cases. The flexible micro-riblet with v-grooves of peak-to-peak spacing of 300 ㎛ was made by MEMS manufacturing process. Five hundred instantaneous velocity fields were measured using PIV cross-correlation technique. The instantaneous velocity fields were ensemble-averaged to get turbulence statistics including turbulence intensities and turbulence kinetic energy. The experimental results were compared with those for a smooth airfoil. Drag acting on the riblet surface was reduced by changing the near-wall flow structure. The net drag reduction evaluated from the wake mean velocity profiles is about 3%.
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MEMS 기술을 이용한 미소 리블렛 필름 제작 및 항력 감소에의 응용
한만희,허정기,이상준,이승섭,Han, Man-Hee,Huh, Jeong-Ki,Lee, Sang-Joon,Lee, Seung-Seop 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.7
This paper presents the fabrication method of a micro-riblet film (MRF) using MEMS technology and the experimental results of the drag reduction of an airfoil with MRFs. Riblets having grooved surface in the streamwise direction has been proven as an effective passive control technique of the drag reduction. A V-grooved pattern on (100) silicon wafer is etched with anisotropic bulk micromachining. The MRF is completed by replicating the V-grooved pattern with polydimethylsiloxane (PDMS). Experiments were performed by measuring a velocity field behind the trailing edge of a NACA 0012 airfoil with and without MRFs in a closed-type subsonic wind tunnel using particle image velocimetry (PlV) technique. The MRF provides about 3.8 % drag reduction compared to the drag on a smooth airfoil when the freestream velocity of wind tunnel is 3.3 m/s.
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Micro-PIV 를 이용한 마이크로 채널 내부 유동의 속도장 측정
이상준(Sang-Joon Lee),허정기(Jeong-Ki Huh),김국배(Guk-bae Kim),이승섭(Seung Seob Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Microfluidic devices made with micromachining technology have been expected to play an important role in bio-industries. As the microfluidics expands, the detail prediction of internal flow structure is highly relevant. In addition, accurate understanding of microscale transport phenomena is important for chemical analysis and biomedical diagnosis. Most microfluidics such as heat sinks for cooling micro-chips, DNA chip, Lab-On-Chip, and micro pumps etc. have microchannels of various size. Therefore, the design of practical microfluidics demands detail information on flow structure inside the microchannels. However, detail velocity field measurements are rare and difficult to carry out. <br/> In this research, Micro-PIV system was employed to measure the velocity fields of flow inside a microchannel. The microchannels were manufactured by MEMS technique. The experiments were carried out for several microchannels of different width(100mm-800mm) and different inlet & outlet configuration. The microchannel with round-type inlet shape gives more smooth entrance flow into the channel, compared with rectangular inlet shape. For the rectangular-type inlet the flow is separated at the inlet edge and has relatively large separated flow region along the channel wall. The dffect of microchannel width(W) on the velocity field in the microchannel is not so high for the microdhannels tested in this study (W≥100㎛). The velocity profiles at x=3/4L downstream location are shown to be nearly fully developed.
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