Poiseuifte's law is

By integrating the velocities of all the concentric rings of flowing blood and multiplying them by the areas of the rings, one can derive the following formula, known as Poiseuille's law: in which F is the rate of blood flow, DP(PA-PB) is the pressure difference between the ends of the vessel, r is the radius of the vessel, l is length of the vessel, and e is viscosity of the blood. F = (PA - PB) pr4/8e4 Ref: Guyton and Hall Textbook of Medical Physiology (12th Edn) page No:309