So the supply air flow rate has a larger effect on the distribution
of the static pressure along the length direction than that on the
total pressure, while the static pressure determines the distribution
of air velocity along the length direction and the total pressure is
positively related with energy consumption and noise level of fan.
Therefore, there exists a threshold value for supply air flow rate for
a given FADS in order to obtain a proper pressure inside FADS and
an economic fan energy consumption.