Question: the velocity distribution in laminar flow through a circular pipe follows the law
Answer: In nonideal fluid dynamics , the Hagen -- Poiseuille equation , also known as the Hagen -- Poiseuille law , Poiseuille law or Poiseuille equation , is a physical law that gives the pressure drop in an incompressible and Newtonian fluid in laminar flow flowing through a long cylindrical pipe of constant cross section .