Conditions for the occurrence of large near-wall excesses of small particles during blood flow

Abstract

Prior work showed that the near-wall concentration of platelet-sized latex beads (2.38 μm diam) in flowing blood suspensions can be greater than three times the concentration in the central region of the flow. Similar methods were used to explore the dependence of the near-wall excess (NWE) of beads on the channel height and suspension composition. The bead diameter, suspending fluid viscosity, and red blood cell deformability were varied; the hematocrit was fixed at 15%. Results showed that NWEs ⩾ three times the central concentration were associated with shear stress, rather than with strain rate, required red cell deformability, and occurred with bead diameters of 2.2 μm or larger. The amplitude of NWEs observed in the 30- and 50-μm channels changed sharply from small to large as the wall shear rate (WSR) was increased, while those observed in 100-μm channels exhibited a more gradual dependence on WSR.