# Hydraulic Diameter

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Hydraulic diameter, abbreviated Dh is normally used when the flow is in non-circular pipe or tubes and channels. Circular pipe has the same pressure drop of a rectangular channel but a greater average velocity. Square or rectangular pipes have a greater weight and a greater pressure drop compared with a circular pipe with the same section. For established shapes, various calculations are linked below.

### Hydraulic Diameter FORMULA

$$\large{ d_h = \frac { 4 A } { P } }$$

Where:

$$\large{ d_h }$$ = hydraulic diameter

$$\large{ A }$$ = cross section area

$$\large{ P }$$ = cross section wetting perimeter