The laminar flow Q' [m^{3}/s] through a pipe with circular cross
section is calculated using:
Where D_{h} is the hydraulic diameter, which is the inner diameter of the pipe. For
different cross sections the hydraulic diameter D_{h} is
calculated using:
where A is the area of the cross section and S the wetted
perimeter. For a rectangular groove with sides a and b
the diameter D_{h} becomes:
and the space formed between two concentric pipes:
The flow through a thin film is calculated using:
