**Fig. 1: Uniform Flow through a Channel**

Specific Energy is normally used for open channels. For uniform flow, **the specific energy of a channel will be constant** when the depth and width of the channel remain constant (y and v will then be constant). Notice the similarities between specific energy for open channels and the Bernoulli Equation.

#### Specific Energy Equation

E = E_P + E_V = y + \frac{V^2}{2g}

*where*

**E**= Energy due to pressure_{P}**E**= Energy Due to velocity_{V}**E**= energy per unit weight with elevation datum taken as the bottom of channel**y**= water depth (ft)**V**= velocity (ft/sec)**g**= gravity

**Since V = Q/A, the Specific Energy Equation can also be written as:**

E = y + \frac{Q^2}{2gA^2}

**Lastly since the area of a rectangular channel can be taken as b*h you can...**

E = y + \frac{Q^2}{2g(bh)^2} \quad \text{ [Rectangular Channels]}

*where*

**b**= the base of the rectangular channel (ft)**h**= the height of the rectangular channel (ft)

## References:

- H. Chanson, "The Hydraulics of Open Chanel Flow: An Introduction (2nd Edition)", 2004