Hydraulic diameter definition in docs

For the local resistant element:

Local Resistance (IL)

The hydraulic diameter is defined as

Is this right? It doesn't even have the units of "m".

Answer 1

[Manas]

Hii,

Yes the Hydraulic diameter defination is correct in the documentation. The unit of the hydraulic diameter depends on the unit of the Flow area

[HiWave]

Well Area is in m^2...doesn't matter about the shape. Plug that in and D is in 1/m? Clearly I'm confused by some definition here. You highlighted "flow area". How is that related to "cross-sectional area"? I looked up "hydraulic diameter" in the engineering toolbox and it says the units are in meters, which makes sense. Please elaborate on your answer for clarity.