Figure 11b. (a) Laminar flow in a vessel of radius r. Flow occurs as a result of pressure differences (P2 - P1) between two points a distance l apart. The velocity of the movement in the center of the vessel is a maximum and follows a parabolic profile to the edge of the vessel wall. (b) Flow in a typical blood vessel follows a blunt profile. The velocity of the flow is relatively uniform over the center of the vessel and falls off at the vessel wall. If a stenosis is present, turbulent flow will result as separation of flow occurs downstream from the stenosis.