- vCommons Home
- Hydraulic diameter of circular duct

# Hydraulic diameter of circular duct

Anastase.Hydraulic diameter of circular duct

The **Hydraulic Diameter of a Circular Duct** calculator computes the hydraulic diameter of a circular duct based on the radius (r) of the duct.

**INSTRUCTION:** Choose units and enter the following:

- (
**r**) This is the radius of the duct.

**Hydraulic Diameter (D _{H}):** The diameter is returned in meters. However, this can be automatically converted to compatible units via the pull-down menu.

#### The Math / Science

Hydraulic diameter of circular duct

dh = 2•r

where:

- dh is the hydraulic diameter of a circular duct
- r is the pipe or duct radius

A hydraulic diameter is useful for dimensionless quantities (e.g. Reynolds number or Gauckler-Manning Equation) which employ a single variable for flow analysis.

Hydraulic diameter is mainly used for calculations involving turbulent flow. Secondary flows can be observed in non-circular ducts as a result of turbulent shear stress in the turbulent flow. Hydraulic diameter is also used in calculation of heat transfer in internal-flow problems.