# Poiseuille′s Equation

The volume flow rate of an incompressible fluid in a round pipe is given by:

Where

Q = volume flow rate [m^{3}s^{-1}]

r = radius of pipe [m]

p_{1}-p_{2} = pressure difference between points 1 and 2 [Nm^{-2}]

μ = dynamic viscosity of fluid [Nsm^{-2}]

L = distance between points 1 and 2 [m]

The velocity profile across the cylinder is seen to be parabolic, and this relation affords a convenient experimental means of determining a fluid′s viscosity.

**See also: **Flow Rate, Pressure, Viscosity.

**Subjects: ** Aerodynamics Physics