ABSTRACT
The critical gap in channel flow is analogous to the critical capillary size in axisymmetric tube flow. However, the motion of cells in a channel is distinctly different from that in the axisymmetric geometry. In the case of tube flow, the cells translate with a velocity that is higher than the mean velocity of the external fluid. In contrast, the velocity of cells in channel flow can be substantially lower than the mean fluid velocity prevailing in the cell’s absence. An explanation is that in the axisymmetric configuration the cell almost completely fills the entire tube cross-section, whereas in channel flow the external fluid can flow around the cell. As a consequence, in the case of channel flow, the volume fraction of cells (tube hematocrit), can be higher than the flow fraction of cells (discharge hematocrit). The opposite is true in the case of tube flow (see Chapter 4).
