Figure 1.

A typical flow profile for the case of stenosis or vasoconstriction (an approximate schematic is shown in the center-top-right area). The entry to such a blockage results in elongational flow (see the Supporting Material for discussion). On the top, there is a graph of both the fluid velocity and the velocity gradient (or elongational flow rate ɛ) along the center of the tube. The maximum elongational rate clearly occurs in the transition region between the different radii (that are bounded by D) and tends toward zero in the regimes where the vessel radius remains constant. The bottom right shows the effect of placing a protein (the red globule) in this sort of flow: in the transition region d, the protein is elongated by the flow field.