Abstract
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.
Similar content being viewed by others
References
Brakke, K. A., 1992, “The Surface Evolver,”Experimental Mathematics, Vol. 1, pp. 141–165.
Buffone, C., Sefiane, K. and Christy, J. R. E., 2004, “Experimental Investigation of the Hydro-dynamics and Stability of an Evaporating Wetting Film Placed in a Temperature Gradient,”Applied Thermal Engineering, Vol. 24, pp. 1157–1170.
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.
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.
Höhmann, C., Stephan, P. C., 2002, “Micro-scale Temperature Measurement at an Evaporating Liquid Meniscus,”Experimental Thermal and Fluid Science, Vol. 26, pp. 157–162.
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.
Lauga, E. and Stone, H. A., 2003, “Effective Slip in Pressure-Driven Stokes Flow,”Journal of Fluid Mechanics, Vol. 489, pp. 55–77.
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.
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.
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
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.
Tretheway, D. C. and Meinhart, C. D., 2002, “Apparent Fluid Slip at Hydrophobic Micro-channel Walls,”Physics of Fluids, Vol. 14, No. 3, pp. L9-L12.
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.
Zhmud, B. V., Tiberg, F. and Hallstensson, K., 2000, “Dynamics of Capillary Rise,”Journal of Colloid and Interface Science, Vol. 228, pp. 263–269.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Kim, S., Jin, S. & Yoo, J.Y. Flow near the meniscus of a pressure-driven water slug in microchannels. J Mech Sci Technol 20, 710–716 (2006). https://doi.org/10.1007/BF02915988
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF02915988