# Wetted Perimeter

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Wetting perimeter is the portion of the channel that is in contact with the fluid flowing.

### Wetted perimeter Formula

$$\large{ P_w = \frac{ A_c }{ r_h } }$$

$$\large{ P_w = 2 \; h \; \sqrt {1 + z^2 } }$$     (hydraulic radius)

Where:

$$\large{ P_w }$$ = wetting perimeter

$$\large{ A_c }$$ = area cross-section of flow

$$\large{ h }$$ = depth of fluid

$$\large{ r_h }$$ = hydraulic radius

$$\large{ z }$$ = width of channel slope