13.20: Bernoulli’s Principle: Applications

There are many devices and situations in which fluid flows at a constant height and so can be analyzed using Bernoulli's principle. These devices include, but are not limited to, entrainment devices and fluid flow measuring devices.

Entrainment devices use a high fluid speed to create low pressures and, thus, entrain one fluid into another. Some examples of these devices are given below:

1. A Bunsen burner uses an adjustable gas nozzle to entrain air for proper combustion.
2. An atomizer uses a squeeze bulb to create a jet of air that entrains drops of perfume.
3. Paint sprayers and carburetors use very similar techniques to move their respective liquids.
4. A common aspirator uses a high-speed stream of water to create a lower-pressure region. Aspirators may be used as suction pumps in dental and surgical situations, for draining a flooded basement, or for reducing the pressure in a vessel.
5. The chimney of a water heater is designed to entrain air into the pipe leading through the ceiling.

Some devices use Bernoulli's principle for the measurement of fluid speed. Examples of these devices include, Prandtl tubes, also known as pitot tubes, Venturi tubes, and a manometer connected to two tubes that are close together and small enough not to disturb the flow.

Bernoulli's principle has several practical applications, such as Bunsen burners, perfume bottles, and fire hose nozzles.

A venturi tube is one such application, used to measure the velocity of a fluid flowing in a pipe.

It consists of a converging part, the throat, and a diverging part.

Two thin vertical tubes are connected to a venturi tube—one before the converging part and one at the throat region.

Its working is based on the continuity equation and Bernoulli's principle.

According to the continuity equation, if the pipe's cross-sectional area decreases, the velocity of the flow must increase.

According to Bernoulli's principle, the increase in flow velocity is accompanied by a decrease in pressure.

So, the pressure near the inlet is high, and the pressure at the center of the throat region is low. The height difference in the level of fluid in the vertical tubes is the measure of pressure difference.

If the cross-sectional areas are known, one can solve these equations to obtain the velocity of the fluid flowing through the tube.