Experiments with the venturi tube revealed that air passing through the tube behaves the same way as water. When the air passes through the tube’s throat (narrow section) it moves faster. When the air moved faster the pressure decreased. That means the greater the speed of the air the les pressure exerted.

Suppose air is moving through a venturi tube that has a small hole in its throat. Tiny bits of paper scattered near the hole will be pushed into the tube because the outside air pressure is greater than the pressure in the throat. The greater the airflow in the throat, the greater the inward will be. This principle is used paint sprayers and car carburetors to move liquid using pressure differences. In an airplane the air moving above the plane is moving faster than the air below. This means that there is a pressure difference as shown by Bernoulli’s principle.

If it’s still difficult to understand, consider your garden hose. Without a nozzle the water flows at a certain rate. With a nozzle the flow of water speeds up.

Another example of how it works is using a bottle of paint and making it into spray paint. There is drop in air pressure around the paint therefore causing it to rise. Meanwhile air is being pushed out of a syringe-like plunger. The air causes the paint to become spray like. This is the venturi effect.

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