# Darcy Friction Factor - Laminar Flow

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Darcy friction factor formulas are equations that allow you to calculate the friction losses in pipe flow and open channel flow.  The Darcy-Weisbach friction factor is to be used in the Darcy-Weibach equation.  The equation on this page should be used only when the flow regime is fully laminar.  If the flow regime is transition flow or turbulant flow, other approximations for the Darcy Friction Factor should be made.

For the purposes of this equation, Reynolds number should be less than 2,000.  When this happens, the fluid particles move in straight, predictable lines and layers of water flow flow over eachother at different speeds with little to no mixing between the layers.

## Darcy Friction Factor - Laminar Flow formula

 $$\large{ f_d = \frac{ 64 }{ Re } }$$

### Where:

$$\large{ f_d }$$ = Darcy friction factor

$$\large{ Re }$$ = Reynolds number