u = [root]{[rho]²·2gh/([rho]² - 1)},
from which the velocity through the throat and the discharge of the
main can be calculated if the areas at A and B are known and h
observed. Thus if the diameters at A and B are 4 and 12 in., the areas
are 12.57 and 113.1 sq. in., and [rho] = 9,
u = [root]81/80 [root](2gh) = 1.007 [root](2gh).
If the observed Venturi head is 12 ft.,
u = 28 ft. per sec.,
and the discharge of the main is