Vortical flow structures induced by red blood cells in capillaries

TL;DR

This study investigates the flow patterns around red blood cells in capillaries, revealing vortex structures and their dependence on cell shape and spacing, combining experiments and simulations for a comprehensive understanding.

Contribution

It provides new experimental and simulation data on vortical flow structures around red blood cells in capillaries, highlighting the influence of cell shape and spacing.

Findings

Vortex structures are observed around red blood cells, especially in slipper shapes.

The rotation frequency of vortices is inversely proportional to the distance between cells.

Experimental results are validated by numerical simulations.

Abstract

Knowledge about the flow field of the plasma around the red blood cells in capillary flow is important for a physical understanding of blood flow and the transport of micro- and nanoparticles and molecules in the flowing plasma. We conduct an experimental study on the flow field around red blood cells in capillary flow that are complemented by simulations of vortical flow between red blood cells. Red blood cells were injected in a 10x12 micrometer rectangular microchannel at a low hematocrit and the flow field around a single or two cells have been characterized thanks to a highspeed camera and by tracking 250 nm nanoparticles in flow behaving as tracers. While the flow field around a steady croissant shape is found to be relatively similar to that of a rigid sphere, the flow field around a slipper shape exhibits a small vortex at the rear of the red blood cell. Even more pronounced are vortex-like structures observed in the central region between two neighboring croissants. Conclusions: The rotation frequency of the vortices is to a good approximation, inversely proportional to the distance between the cells. Our experimental data are confirmed and complemented by numerical simulations.