# Hydraulic radius

From QueensMineDesignWiki

The

**hydraulic radius**is a measure of a channel flow efficiency. Flow speed along the channel depends on its cross-sectional shape (among other factors), and the hydraulic radius is a characterisation of the channel that intends to capture such efficiency. Based on the 'constant shear stress at the boundary' assumption,^{[1]}hydraulic radius is defined as the ratio of the channel's cross-sectional area of the flow to its wetted perimeter (the portion of the cross-section's perimeter that is "wet"):- ↑ An Introduction to Hydrodynamics & Water Waves, Bernard Le Méhauté, Springer - Verlag, 1976, p. 84