Wetted Perimeter

Wetting perimeter, abbreviated as P_w, is the portion of the channel or pipe that is in contact with the fluid flowing.

 

Wetting perimeter formula

\(\large{ P_w = \frac{ A_c }{ r_h }   }\)

Where:

Units	English	Metric
\(\large{ P_w }\) = wetting perimeter	\(\large{ ft }\)	\(\large{ m }\)
\(\large{ A_c }\) = area cross-section of flow	\(\large{ ft^2 }\)	\(\large{ m^2 }\)
\(\large{ r_h }\) = hydraulic radius	\(\large{ ft }\)	\(\large{ m }\)

 

Related Wetted perimeter formulas

\(\large{ P_w = 2 \; h \; \sqrt  {1  +  z^2 }  }\)	(hydraulic radius)
\(\large{ P_w =  r \;  \theta }\)	(Hydraulic Radius of a Partially Full Pipe (Less than Half Full))
\(\large{ P_w =  2 \; \pi \; r  - r \;  \theta }\)	(Hydraulic Radius of a Partially Full Pipe (More than Half Full))

Where:

\(\large{ P_w }\) = wetting perimeter

\(\large{ \theta }\)   (Greek symbol theta) = degree

\(\large{ h }\) = depth of fluid

\(\large{ \pi }\) = Pi

\(\large{ r }\) = radius

\(\large{ z }\) = width of channel slope