| Abstract: | I investigate the effect of tube diameter D and red blood cell capillary number Ca (i.e. the ratio of viscous to elastic forces) on platelet margination in blood flow at ≈37 % tube haematocrit. The system is modelled as three-dimensional suspension of deformable red blood cells and nearly rigid platelets using a combination of the lattice-Boltzmann, immersed boundary and finite element methods. Results of simulations during the dynamics before the steady state has been reached show that a non-diffusive radial platelet transport facilitates margination. This non-diffusive effect is important near the edge of the cell-free layer, but only for Ca > 0.2, when red blood cells are tank-treading. I also show that platelet trapping in the cell-free layer is reversible for Ca ≤ 0.2. Margination is essentially independent of Ca only for the smallest investigated tube diameter (D = 10 μm). Once platelets have reached the cell-free layer, they tend to slide rather than tumble. The tumbling rate is essentially independent of Ca but increases with D. Strong confinement suppresses tumbling due to the relatively small cell-free layer thickness at ≈ 37 % tube haematocrit. |
