Effects of RBC hematocrit and aggregation on viscosity and blood flow velocity.

(A) Snapshots of RBC arrangement and velocity driven by steady state 9.6 Pa pressure drop from left to right ends of the vessel segment (30 μm in diameter and 150 μm in length) under 10 and 20% hematocrits (i) and the time-averaged blood velocity plot in the cross-sectional lumen at the middle of the vessel length (ii). (B) Snapshots of RBC rouleaux formation and velocity under 20% hematocrits and 1 μJ/m2 aggregation levels (i) and the time-averaged blood velocity plot in the cross-sectional lumen at the middle of the vessel length (ii). (C) Plot of relative apparent viscosity against hematocrit for blood with and without RBC aggregation. Movies of the four conditions simulated can be viewed in S3–S5 Movies. (D) Flow retardation effect of RBCs in blood flow and the flow blunting effects of RBC aggregation on the cross-sectional velocity profile under constant segment pressure drop conditions.