Journal of Mechanical Science and Technology

  • 제20권5호
  • /
  • Pages.710-716
  • /
  • 2006
  • /
  • 1738-494X(pISSN)
  • /
  • 1976-3824(eISSN)
대한기계학회 (The Korean Society of Mechanical Engineers)
권호 표지

Flow Near the Meniscus of a Pressure-Driven Water Slug in Microchannels

  • Kim Sung-Wook (Samsung Advanced Institute of Technology) ;
  • Jin Song-Wan (School of Mechanical and Aerospace Engineering, Seoul National University) ;
  • Yoo Jung-Yul (School of Mechanical and Aerospace Engineering, Seoul National University)
  • 발행 : 2006.05.01
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

Micro-PIV system with a high speed CCD camera is used to measure the flow field near the advancing meniscus of a water slug in microchannels. Image shifting technique combined with meniscus detecting technique is proposed to measure the relative velocity of the liquid near the meniscus in a moving reference frame. The proposed method is applied to an advancing front of a slug in microchannels with rectangular cross section. In the case of hydrophilic channel, strong flow from the center to the side wall along the meniscus occurs, while in the case of the hydrophobic channel, the fluid flows in the opposite direction. Further, the velocity near the side wall is higher than the center region velocity, exhibiting the characteristics of a strong shear-driven flow. This phenomenon is explained to be due to the existence of small gaps between the slug and the channel wall at each capillary corner so that the gas flows through the gaps inducing high shear on the slug surface. Simulation of the shape of a static droplet inside a cubic cell obtained by using the Surface Evolver program is supportive of the existence of the gap at the rectangular capillary corners. The flow fields in the circular capillary, in which no such gap exists, are also measured. The results show that a similar flow pattern to that of the hydrophilic rectangular capillary (i.e., center-to-wall flow) is always exhibited regardless of the wettability of the channel wall, which is also indicative of the validity of the above-mentioned assertion.

키워드

참고문헌

  1. Brakke, K. A., 1992, 'The Surface Evolver,' Experimental Mathematics, Vol. 1, pp. 141-165 https://doi.org/10.1080/10586458.1992.10504253
  2. Buffone, C., Sefiane, K. and Christy, J. R. E., 2004, 'Experimental Investigation of the Hydrodynamics and Stability of an Evaporating Wetting Film Placed in a Temperature Gradient,' Applied Thermal Engineering, Vol. 24, pp. 1157-1170 https://doi.org/10.1016/j.applthermaleng.2003.10.038
  3. Buffone, C., Sefiane, K., 2004a, 'IR Measurements of Interfacial Temperature during Phase Change in a Confined Environment,' Experimental Thermal and Fluid Science, Vol. 29, pp. 65-74 https://doi.org/10.1016/j.expthermflusci.2004.02.004
  4. Buffone, C., Sefiane, K., 2004b, 'Investigation of Thermocapillary Convection Patterns and Their Role in the Enhancement of Evaporation from Pores,' International Journal of Multiphase Flow, Vol. 30, pp. 1071-1091 https://doi.org/10.1016/j.ijmultiphaseflow.2004.05.010
  5. Hohmann, C., Stephan, P. C., 2002, 'Microscale Temperature Measurement at an Evaporating Liquid Meniscus,' Experimental Thermal and Fluid Science, Vol. 26, pp. 157-162 https://doi.org/10.1016/S0894-1777(02)00122-X
  6. Jin, S., Huang, P., Park, J., Yoo, J. Y. and Breuer, K. S., 2004, 'Near-Surface Velocimetry Using Evanescent Wave Illumination,' Experiments in Fluids, Vol. 37, pp. 825-833 https://doi.org/10.1007/s00348-004-0870-7
  7. Lauga, E. and Stone, H. A., 2003, 'Effective Slip in Pressure-Driven Stokes Flow,' Journal of Fluid Mechanics, Vol. 489, pp. 55-77 https://doi.org/10.1017/S0022112003004695
  8. Park, J. S., Choi, C. K., Kihm, K. D. and Allen, J. S., 2003, 'Optically-Sectioned Micro PIV Measurements Using CLSM,' Journal of Heat Transfer, Vol. 125, p. 542 https://doi.org/10.1115/1.1617071
  9. Park, J. S., Kim, H. J. and Kihm, K. D., 2001, 'Molecular Tagging Fluorescence Velocimetry？(MTFV) for Lagrangian Flow Field Mapping Inside Evaporating Meniscus : Potential Use for Micro-Scale Applications,' Journal of Flow Visualization and Image Processing, Vol. 8, pp. 177-187
  10. Silnerzan, P., Leger, L., Ausserre, D. and Benattar, J. J., 1991, 'Silanation of Silica Surfaces. A New Method of Constructing Pure or Mixed Monolayers,' Langmuir, Vol. 7, pp. 1647-1651 https://doi.org/10.1021/la00056a017
  11. Sung, J. and Yoo, J. Y., 2001, 'Three-Dimensional Phase Averaging of Time-Resolved PIV Measurement Data,' Measurement Science and Technology, Vol. 12, pp. 655-662 https://doi.org/10.1088/0957-0233/12/6/301
  12. Tretheway, D. C. and Meinhart, C. D., 2002, 'Apparent Fluid Slip at Hydrophobic Microchannel Walls,' Physics of Fluids, Vol. 14, No. 3, pp. L9-L12 https://doi.org/10.1063/1.1432696
  13. Tyrrell, J. W. G. and Attard, P., 2001, 'Images of Nanobubbles on Hydrophobic Surfaces and Their Interactions,' Physical Review Letters, Vol. 87, No. 17, 176104 https://doi.org/10.1103/PhysRevLett.87.176104
  14. Zhmud, B. V., Tiberg, F. and Hallstensson, K., 2000, 'Dynamics of Capillary Rise,' Journal of Colloid and Interface Science, Vol. 228, pp. 263-269 https://doi.org/10.1006/jcis.2000.6951