# 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 $\Delta P=\frac{\rho fLv^2}{2d}$ Where: - $\Delta P$ = pressure loss due to friction (Pa) - $f$ = friction factor - $L$ = pipe length (m) - $d$ = pipe diameter (m) - $v$ = fluid bulk (average) velocity (m/s) ## Head loss form $\Delta h_{f}=\frac{fLv^2}{2dg}$ Where: - $\Delta h_{f}$ = head loss due to friction (m) - $f$ = friction factor - $L$ = pipe length (m) - $d$ = pipe diameter (m) - $v$ = fluid bulk (average) velocity (m/s) - $g$ = acceleration due to gravity ($m/s^2$)