Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Hydraulic radius ( $$r_h$$ ) is the cross section area of water in a pipe or channel divided by the wetting perimeter.

$$r_h = \frac { A } { P_w }$$

Where:

$$r_h$$ = hydraulic radius

$$A$$ = area of cross section flow

$$P_w$$ = wetted perimeter

Solve for:

$$A = r_h P_w$$

$$P_w = \frac { A } { r_h}$$