# Darcy-Weisbach Equation

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Darcy-Weisbach Equation ( $$DW$$ ) (dimensionless number) is the most common way of expressing the pressure drop of a piped fluid is to use the.  The equation is valid for fully developed, steady state and incompressible flow. The Darcy-Weisbach equation with the Moody Diagram are considered to be the most accurate model for estimating frictional head loss in steady pipe flow.

### Darcy-Weisbach Equation FORMULA

$$\large{ h_l = \frac { f l v^2 } { D g } }$$

Where:

$$\large{ h_f }$$ = head loss due to friction

$$\large{ f }$$ = friction factor

$$\large{ g }$$ = gravitational acceleration

$$\large{ D }$$ = inside diameter

$$\large{ l }$$ = length

$$\large{ v }$$ = velocity of the fluid

Solve for:

$$\large{ f = \frac { 2 {h_f} D g } { l {v^2} } }$$

$$\large{ l = \frac { 2 {h_f} D g } { f v^2 } }$$

$$\large{ D = \frac { f l v^2 } { 2 {h_f} g } }$$

$$\large{ v = \sqrt { \frac { 2 {h_f} D g } { fl } } }$$

$$\large{ g = \frac { f l v^2 } { 2 {h_f} D } }$$