The Bernoulli Principle is also responsible for the functioning of airplane wings, which work because of differential pressure of air over flat vs. curved sides of wings.

The Bernoulli Principle is a way of using physics to describe the flow rate, pressure, and speed of moving liquids and gases, and it underlies the accurate functioning of Venturi differential flow meters.

It describes a very reliable and predictable relationship between the speed and pressure of moving fluids as they pass over, around, or through objects and surfaces.

To put it in the context of flow metering: when the passage of a moving fluid is restricted by an object or a restricted section of a channel, two things happen in a predictable manner:

  • The speed of the fluid increases as it passes through the more-restricted channel section, relative to speed through a less-restricted channel
  • The pressure of the fluid decreases as it passes through the more-restricted channel section, relative to pressure through a less-restricted channel

This creates a pressure difference in the fluid as it flows through a restricted section of channel. If one were to take simultaneous measurements of line fluids as they pass through wider and narrower spaces, it would yield a pressure differential between the two readings.

This process happens more strongly under greater flow conditions than under lesser ones, also in a predictable manner. Thus:

  • It is possible to correlate the flow rate of a fluid with its pressure differential as it passes from a more open channel to a more restricted channel

A “differential flow meter”, like a venturi tubes or an orifice plate, is called “differential” because it works by restricting the flow rate of line fluids in a controlled manner, and measuring the pressure differential between the “upstream” less-restricted channel, and the more-restricted channel (the throat of a venturi, or behind an orifice plate). 

Through exact calculations, PFS can produce differential pressure meters, based on the Bernoulli Principle, and the accuracy of these meters is impeccable because they are based on this basic and reliable principle of fluid dynamics.



Orifice Meter Tube


Orifice Plate