Abstract
The lateral migration of elastic capsules towards a microchannel centerline plays a major role in industrial and physiological processes. Via our computational investigation, we show that a constriction connecting two straight microchannels facilitates the lateral capsule migration considerably, which is relatively slow in straight channels. Our work reveals that the significant cross-streamline migration inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size. However, in the downstream straight channel, the increased interfacial deformation at higher capillary numbers or a lower viscosity ratio and lower membrane hardness results in increased lateral cross-streamline migration. Thus, our work highlights the different migration mechanisms occurring over curved and straight streamlines.
Highlights
The study of the interfacial dynamics of artificial or physiological capsules in viscous flows has seen increased interest during the last few decades, owing to their numerous engineering and biomedical applications [1,2]
Our investigation shows that the significant cross-streamline migration over the curved streamlines inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size
The interfacial deformation does facilitate the lateral migration over the straight streamlines of the downstream straight channel, as our results for varying capillary number, viscosity ratio and membrane hardness reveal
Summary
The study of the interfacial dynamics of artificial or physiological capsules (i.e., membrane-enclosed fluid volumes) in viscous flows has seen increased interest during the last few decades, owing to their numerous engineering and biomedical applications [1,2]. In the area of interest of the present work, the flow-induced lateral migration of soft particles (such as droplets, elastic capsules, vesicles or erythrocytes) plays a significant role in industrial and physiological processes [3,4,5,6]. To facilitate the cross-streamline migration towards the channel centerline, in this work we propose flowing elastic capsules in a converging micro-capillary of comparable size under Stokes flow conditions. The interfacial deformation does facilitate the lateral migration over the straight streamlines of the downstream straight channel, as our results for varying capillary number, viscosity ratio and membrane hardness reveal
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