# Blog Archives

## Closed Conduit Hydraulics – Friction and Minor Losses

Friction and minor losses are glossed over in the darcy-weisbach article but I want to throw in some extra notes here. Friction occurs over every bit of length of a close-conduit system and is usually a surprisingly high amount of energy loss. Friction depends on the material of the pipe and the velocity of flow. The formula for frictional head loss IS the Darcy-Weisbach equation.

$$h_f = f \frac{L}{D}\frac{V^2}{2g}$$

## Closed Conduit Hydraulics – Darcy-Weisbach Equation

The Darcy-Weisbach equation is used to determine flow characteristics in closed conduit systems (pipes). It is probably more common than the Hazen-Williams equation due to it being able to solve for systems in both laminar AND turbulent flow.

$$h_f = f \frac{L}{D} \frac{V^2}{2g}$$

• headloss $$h_f$$ (ft)
• friction factor $$f$$, length $$L$$
• length $$L$$ (ft)
• diameter $$D$$ (ft)
• velocity $$V$$ \frac{ft}{s}\)
• gravity g $$32.2 \frac{ft}{s^2}$$

#### Friction Factor

The friction factor $$f is either given or must be calculated using a Moody-Stanton diagram (available in both the AIO and CERM). Getting the friction factor from a Moody-Stanton chart requires the Reynolds Number \(Re$$, and relative roughness $$\frac{\epsilon}{D}$$. Click here to continue reading