EXPERIMENTAL INVESTIGATION OF THE FLOW FRONT BEHIND A LIQUID-AIR INTERFACE FOR CAPILLARY FLOW

An experimental system for understanding the flow field near the meniscus during the capillarity or under capillary action is developed. Capillary flow is one of the mechanisms for driving fluid in a microfluidic device. The literature highlights that a significant amount of work has been done on the theoretical understanding of the capillary transport in rectangular microchannels. However, these models for capillary flow neglect the flow behavior at the liquid-air interface, which may have a significant influence in terms of the velocity field and the transience of the penetration depth in the micro-capillary. The objective of the present study is to understand the flow development during the advancement of the meniscus. The aim is to elucidate the dynamics of the three phase contact line and other micro-scale effects during the capillarity. A mu- PIV technique has been used to study the flow development near the meniscus and the results are further refined using a hybrid mu-PIV/PTV technique. Effects of surface tension in the fully developed flow regime during the advancement of meniscus are studied in detail. Variations in the centreline velocity of the progression of the meniscus and temporal variations in the development of flow are identified as possible areas for departure from theory.