Migration of liquid drops through narrow passages and flow dynamics of cancer cells through constricted microchannels

Abstract

The aims of the present dissertation is to understand the ow dynamics of deformable drops as well as cancer cells in microchannels. In this regard, we study the motion and deformation of a neutrally buoyant drop in a microchannel both in the absence and presence of electric fields, tuning the various hydrodynamic and electrical properties in the first part of the thesis. The problems in the first part have been extensively investigated using numerical analysis. In the other part, we extend our understanding of motion of deformable drops in microchannels to investigate the flow behavior of cancer cells through constricted microchannels. Different biological assays are performed to analyze the metastatic potency of the cells after passing through the constriction. The study on this latter part opens up a horizon for further investigations; this class of flows is becoming increasingly relevant with advances in medical engineering and nanofluidics. The prime focus of the first problem of interest is to investigate the migration and break up of a neutrally buoyant droplet in a tube containing another immiscible liquid in the creeping ow. The interface between the two immiscible fluids has been captured using a coupled level-set and volume-of-fluid (CLSVOF) approach. The deformation and breakup dynamics of the droplet have been investigated in terms of three dimensionless parameters, namely, the ratio between the radius of the undeformed droplet and the radius of the capillary tube, the viscosity ratio between the dispersed and the continuous phases, and the capillary number that measures the relative importance of the viscous force over the surface tension force. A thorough computational study has been conducted to find the critical capillary number for a range of droplets of varied sizes suspended in flows having different viscosity ratios. Next, the cross-stream migration phenomenon exhibited by a two-dimensional drop is studied. The multiphase modeling is done adopting the volume-of-fluid(VOF) interface capturing method. In the absence of electric field, the important non-dimensional parameters pertaining to such two-phase flows are viscosity ratio between the drop fluid and the surrounding medium, the ratio of drop diameter to channel height and the capillary number. The influence of all these parameters in drop migration has been studied by varying the parameters in a wide range along with varied initial off-center positions. The presence of electric field introduces additional stresses at the drop interface and its effect on drop migration has been investigated by solving the electro-hydrodynamic Navier-Stokes equations.