Equation of Continuity:
The calibrations of many of the flowmeters described earlier are based on the equation of continuity and Bernoulli’s equation.
The equation of continuity states that for the steady flow of a fluid through a pipe of varying cross-section the rate of mass entering the pipe must be equal to the
rate of mass leaving the pipe; this is really a statement of the principle of conservation of mass.
Thus, for an incompressible fluid: A1V1 =A2V2
where A1 = cross-sectional area at section 1,
A2 = cross-sectional area at section 2,
v1 = velocity of fluid at section 1, and v2 = velocity of fluid at section 2
