Venturi meters are used to measure flow rates by using a converging section of pipe. As the fluid flows through the convergence, the fluids velocity increases, and the fluids pressure drops accordingly. Using the Bernoulli equation, the flow rate can be determined. Venturi meters have been used in industry for many years, particularly in water supply applications. Venturi meters are preferred to simpler methods of flow rate measurement (for example, orifice plates) because they cause less pressure loss in the system, saving energy (compressing fluids requires a significant amount of energy). However, they are more susceptible to errors due to deposits at the throat and are more expensive.

The cross-sectional area of the pipe can be calculated by

areapipe=dp24

where d_p is the diameter of the pipe in cm.

The cross-sectional area of the throat, then, can be calculated using

areathroat=dt24

where d_t is the diameter of the throat in cm.

The throat-to-pipe diameter ratio is calculated by

ratio=areapipeareathroat

This ratio, along with the pressure drop h in cm, is used to calculate the discharge rate Q (cm³/sec):

Q=25*1960*hratio2-1

For this program, use a constant pressure drop of 5 cm (define this as a preprocessor constant). Also define pi as a preprocessor constant (3.14159).