and is used in the square law for pressure drop, where (in English units) One atkinson is defined as the resistance of an airway which, when air flows along it at a rate of 1,000 cubic feet per second, causes a pressure drop of one pound-force per square foot.
The unit is named after J J Atkinson, who published one of the earliest comprehensive mathematical treatments of mine ventilation.
Atkinson based his expressions for airflow resistance on the more general work of Chézy and Darcy who defined frictional pressure drop as where The practicalities of mine ventilation led Atkinson to group some of these variables into one all-encompassing term: The resulting term is one that can be easily calculated from the results of two simple measurements: a pressure survey by the gauge and tube method and a flowrate survey with a counting anemometer.
It, too, is termed the atkinson resistance but the unit was given the name gaul (for reasons unknown).
One gaul is defined as the resistance of an airway which, when air (of density 1.2 kg/m3) flows along it at a rate of one cubic metre per second, causes a pressure drop of one pascal.