*** Welcome to piglix ***

Darcy–Weisbach equation


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 for an incompressible fluid. The equation is named after Henry Darcy and Julius Weisbach.

The Darcy–Weisbach equation contains a dimensionless friction factor, known as the Darcy friction factor. This is also variously called the Darcy–Weisbach friction factor, friction factor, resistance coefficient, or flow coefficient.

In a cylindrical pipe of uniform diameter D, flowing full, the pressure loss due to viscous effects Δp is proportional to length L and can be characterized by the Darcy–Weisbach equation:

where the pressure loss per unit length Δp/L (SI units: Pa/m) is a function of:

For laminar flow, this can be rewritten to

where

The head loss Δh (or hf) expresses the pressure loss due to friction in terms of the equivalent height of a column of the working fluid, so the pressure loss is

where

It is useful to present head loss per length of pipe (dimensionless):

where L is the pipe length (m).


...
Wikipedia

...