• Title/Summary/Keyword: 마이크로유동

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Characterization of Bi-directionally Oscillating Microflow and Flow Rectification Performance of Microdiffusers (마이크로 디퓨저 내의 양 방향 동적 유동과 펌프 구동 주파수에 따른 유동정류 특성 연구)

  • Lee, Yeong-Ho;Gang, Tae-Gu;Jo, Yeong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.2
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    • pp.291-299
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    • 2002
  • This paper characterizes hi-directionally oscillating flow in planar microdiffusers in order to evaluate the frequency-dependent flow rectification performance of the microdiffusers. In the theoretical study, we analyze a hi-directionally oscillating flow in the planar microdiffuser. In the experimental study, we fabricate two different microdiffuser prototypes, having different neck widths of 100 ㎛ (D100) and 300 ㎛(D300), respectively. The experimental net flow rates are measured as 116.6 $\mu$ι/min. and 344.4 $\mu$ι/min. for D100 and D300, respectively. The experimental flow rate of D300 decreases at the oscillating flow frequencies higher than 90Hz, at which the net boundary layer thickness is reduced to the microdiffuser neck width. It is experimentally verified that the flow rectification performance and the net flow rate of the microdiffusers tend to decrease when the boundary layer thickness is smaller than the diffuser neck width.

${\mu}-PIV$ Visualization of Flow in Hydrophilic and Hydrophobic Micro-nozzle (친수성 및 소수성 마이크로 노즐 내 유동 ${\mu}-PIV$ 연구)

  • Byun, Do-Young;Kim, Ji-Hoon
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.15-18
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    • 2006
  • Recently, experimental visualization of microscale fluid transport has attacted considerable attention in designing microelectromechanical systems. Fluid-surface interactions on hydrophobic and hydrophilic surfaces can play a key role in passively controlling microfluidics. Here we investigate the slip boundary condition depending on the surface characteristics; hydrophilic, hydrophobic wettabilities. Using the micro-PIV, velocity profiles are measured in the glass (hydrophilic), PDMS (hydrophobic) microchannels.

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Simultaneous Measurement of Internal and External Flow Fields around the Droplet Formation in a Microchannel (마이크로 채널 내 Droplet 형성에 따른 내${\cdot}$외부 유동장 동시측정)

  • Kim Kyung Chun;Kim Jae Min;Yoon Sang Youl
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.80-83
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    • 2004
  • This experiment has been carried out to measure the process of droplet formation between water phase fluid$(PVA\;3\%)$ and organic phase fluid(oil), Internal and External flow fields measured by a Dynamic Micro-PIV method Water-in-oil(W/O) droplets successfully generated at a cross junction and Y junction. Internal and external flow fields were measured when the droplet grew up, stretched and separated.

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Heat transfer characteristic and flow pattern investigation in micro-channels during two-phase flow boiling (이상 유동 비등 시 마이크로 채널에서의 열전달 특성과 유동양식 조사)

  • Choi, Yong-Seok;Lim, Tae-Woo
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.7
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    • pp.696-701
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    • 2015
  • Two-phase flow boiling experiments were conducted in 15 micro-channels with a depth of 0.2 mm, width of 0.45 mm, and length of 60 mm. FC-72 was used as the working fluid, and the mass fluxes ranged from 200 to $400kg/m^2s$. Tests were performed over a heat flux range of $5-40kW/m^2$ and vapor quality range of 0.1-0.9. The heat transfer coefficient sharply decreased at a lower heat flux and then was kept approximately constant as the heat flux is increased. Based on the measured heat transfer data, the flow pattern was simply classified into bubbly, slug, churn, and wavy/annular flows using the existing method. In addition, these classified results were compared to the transition criterion to wavy/annular regime. However, it was found that the existing transition criterion did not satisfactorily predict the transition criterion to annular regime for the present data.

STUDY ON TWO-DIMENSIONAL LAMINAR FLOW PAST A VERTICAL PLATE IN A MICROCHANNEL (마이크로채널 내의 수직 평판을 지나는 2차원 층류유동장에 대한 연구)

  • Yoon, Seok-Hyun;Jeong, Jae-Tack
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.233-238
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    • 2010
  • A two-dimensional laminar flow past a vertical plate in a microchannel is investigated. At far upstream and downstream from the plate in the microchannel, the plane Poiseuille flow exists. The Stokes flow for this microchannel is investigated analytically and then the laminar flow by numerical method. For the Stokes flow analysis, the method of eigenfunction expansion is used. From the results, the streamline pattern and the pressure distribution are plotted, and the additional pressure drop induced by the plate and the force exerted on the plate are calculated as functions of the length of the plate. For the laminar flow, finite difference method (FDM) is used to obtain the vorticity and the stream function. When the Reynolds number exceeds a critical value, a pair of viscous eddies appears behind the plate.

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A Fundamental Study of Compressible Micro Flows (압축성 마이크로 유동에 관한 기초 연구)

  • Kim Jae Hyung;Jeong Mi Seon;Kim Heuy Dong;Park Kyung Am
    • Proceedings of the KSME Conference
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    • 2002.08a
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    • pp.143-146
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    • 2002
  • Recently the micro flows have been received much attention in the applications with regard to Micro Electro Mechanical Systems(MEMS). Such flows are governed by relatively large viscous forces, compared with inetia force, and frequently specified by slip wall boundary conditions. In the present study, computations are applied to investigate the compressible viscous flows through an extremely small channel, and theoretical analyses are conducted using the Fanno flow theory. The axisymmetic, compressible, Wavier-Stokes equations are numerically solved by a fully implicit finite implicit method. The predicted results are validated with previous experimental data available. The results obtained show that for small Reynolds numbers, the viscous frictional force significantly influences the compressible micro channel flows.

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flow analysis in Micro Channel with a Couple of Fins (박막이 부착된 마이크로 채널 내의 유동해석)

  • Jeong Jae-Tack
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.228-233
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    • 2005
  • Two-dimensional Stokes flows through a micro channel with a couple of symmetric vertical fins are investigated. At far up- and down-stream from the fins, the plane Poiseuille flow exists in the channel. The slip boundary conditions are applied to take account of the Knudsen number effects. For the analysis, the method of eigen function expansion and collocation method are employed. By the results, the streamline patterns and pressure distributions are shown and the force exerted on the fin and the excess pressure drop due to the fins are determined as functions of the length of the fin and Knudsen number. It may be conjectured that the force and the excess pressure drop are almost independent of the Knudsen number.

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Flow Analysis and Process Conditions Optimization in a Cavity during Semiconductor Chip Encapsulation (반도체 칩 캡슐화성형 유동해석 및 성형조건 최적화에 관한 연구)

  • 허용정
    • Journal of the Microelectronics and Packaging Society
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    • v.8 no.4
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    • pp.67-72
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    • 2001
  • An Effort has been made to more accurately analyze the flow in the chip cavity, particularly to model the flow through the openings in the leadframe and correctly treat the thermal boundary condition at the leadframe. The theoretical analysis of the flow has been done by using the Hele-Shaw approximation in each cavity separated by a leadframe. The cross-flow through the openings in the leadframe has been incorporated into the Hele-Shaw formulation as a mass source term. The optimization program based on the complex method integrated with flow analysis program has been successfully used to obtain the optimal filling conditions to avoid short shot.

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Numerical Analysis of Grout Flow and Injection Pressure Affected by Joint Roughness and Aperture (절리 거칠기와 간극 변화에 따른 그라우트 유동과 주입압에 관한 수치해석적 연구)

  • Jeon, Ki-Hwan;Ryu, Dong-Woo;Kim, Hyung-Mok;Park, Eui-Seob;Song, Jae-Jun
    • Tunnel and Underground Space
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    • v.20 no.2
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    • pp.82-91
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    • 2010
  • Grouting technology is one of the ground improvement methods used in water controlling and reinforcement of rock mass in underground structure construction. It is necessarily required to find out the characteristics of grout flow through discontinuities in a rock mass for an adequate grout design and performance assessment. Laminar flow is not always applicable in simulating a grout flow in a rock mass, since the rock joints usually have apertures at a micro-scale and the flow through these joints is affected by the joint roughness and the velocity profile of the flow changes partially near the roughness. Thus, the influence of joint roughness and aperture on the grout flow in rough rock joint was numerically investigated in this study. The commercial computational fluid dynamics code, FLUENT, was applied for this purpose. The computed results by embedded Herschel-Bulkley model and VOF (volume of fluid) model, which are applicable to simulate grout flow in a narrow rock joint that is filled with air and water, were well compared with that of analytical results and previously published laboratory test for the verification. The injection pressure required to keep constant injection rate of grout was calculated in a variety of Joint Roughness Coefficient (JRC) and aperture conditions, and the effect of joint roughness and aperture on grout flow were quantified.