Darcy-Weisbach equation

In fluid dynamics, the Darcy–Weisbach equation is an empirical equation that relates the head loss, or pressure loss, due to friction along a given length of pipe to the average velocity of the fluid flow for an incompressible fluid.

Pressure loss form

Where:

• = pressure loss due to friction (Pa)
• = friction factor
• = pipe length (m)
• = pipe diameter (m)
• = fluid bulk (average) velocity (m/s)

Head loss form

Where:

• = head loss due to friction (m)
• = friction factor
• = pipe length (m)
• = pipe diameter (m)
• = fluid bulk (average) velocity (m/s)
• = acceleration due to gravity ()