Darcy Weisbach equation (head loss)
In fluid dynamics, the Darcy–Weisbach equation is a phenomenological equation, which relates the head loss — or pressure loss — due to friction along a given length of pipe to the average velocity of the fluid flow.
Darcy friction factor can be found from a Moody diagram
|Head loss (m)
|Darcy friction factor (see diagram) (dimensionless)
|Length of the pipe (m)
|Hydraulic diameter (m)
|Average velocity of the fluid flow (m/s)