Since there is some energy loss between point(1) to point(2) Then, the actual flow will be less than the above ideal flow, and after applying the coefficient of discharge Ca to the ideal flow, the actual flow will be
actual flow rate
coefficient of discharge of Venturi meter,dimensionless constant
throat cross section area,
pipe diameter
throat diameter,
pressure at section
pressure at section
specific weight of fluid,
elevation of section
elevation of section
acceleration due to gravity
so equation(3-14) will be