Interfacial Flows of Contact Line Dynamics and Liquid Displacement in a Circular Microchannel

Abstract

-In this paper, we report experimental and analytical studies of the interfacial flows of contact line dynamics and liquid film displacement of gas-liquid two-phase flows in a capillary tube. To quantitatively measure and analyse the interfacial liquid film displacement behaviour, an optical technique for measuring the interfacial liquid film between the liquid and gas in a capillary tube has been developed. The interfacial film dynamics is detected by a very sensitive laser spatial fringe projection technique and a high speed camera. The spatial frequencies of the fringe patterns are calculated utilizing image processing technique which are used to determine the interfacial film thickness between the gas plug and the channel wall. The uncertainty of the measurements is less than several hundred nanometres. Because the resolution of the film measurements is very high, it is possible to determine whether a liquid film exists or not for different flow capillary numbers, therefore, the critical capillary numbers can be determined. Pressure-driven flow model is used to analyse the interfacial evolution and the contact line motion. It is found that the critical capillary number is affected by the surface tension of liquids and wall surface wettability. The newly developed analytical model is validated by experimental results utilizing the interfacial film measurement technique.