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 called the Darcy–Weisbach friction factor, resistance coefficient, or simply friction factor.
Pressure loss form
In a cylindrical pipe of uniform diameter D, the pressure loss due to viscous effects Δp is proportional to length L and can be characterized by the Darcy Weisbach equation:
where the loss per unit length Δp/L (SI units Pa/m) is a function of:
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