Effects of surface topography on low Reynolds number droplet/bubble flow through constricted passage

This paper is an attempt to study the effects of surface topography on the flow of a droplet (or a bubble) in a low Reynolds number flow regime. Multiphase flows through a constricted passage find many interesting applications in chemistry and biology. The main parameters which determine the flow properties such as flow rate and pressure drop, and govern the complex multiphase phenomena such as drop coalescence, break-up and snap-off in a straight channel flow are the viscosity ratio, droplet size and ratio of the viscous forces to the surface tension forces (denoted by Capillary number). But in flow through a constricted passage, various other parameters such as constriction ratio, length and shape of the constriction, phase angle, and spacing between the constrictions also start playing an important role. An attempt has been made to review and summarize the present knowledge on these aspects and by mentioning what all lacks in the literature that could be studied further.