- Hydraulic diameter
The hydraulic diameter, , is a commonly used term when handling
flowin noncircular tubes and channels. Using this term one can calculatemany things in the same way as for a round tube.
where "A" is the cross sectional
areaand "U" is the wetted perimeterof the cross-section.
For a round tube, this checks as:
Manning formulacontains a quantity called the hydraulic radius. Despite what the name may suggest, the hydraulic diameter is not twice the hydraulic radius.
For an annulus the hydraulic diameter is
and for a rectangular duct
For the special case of a square duct, where , then . For the other limiting case of a very wide duct, i.e. a slot of width where , then .
Wikimedia Foundation. 2010.