The Venturi effect was described scientifically by Giovanni Battista Venturi.
He stated that fluids under pressure passing through converging pipes gain speed and lose head and vice versa for diverging pipes. Venturi was a very bright man, his ingenuity can be understood when he.s describing the Venturi effect and stating that fluid is under pressure.
This means that there should be a pressure difference in the pipe for the fluid to flow.
Most of the videos on the internet explain the Venturi effect by using Bernoulli.s famous equation seen here.
By using this formula we can show that the pressure at the point P two is less than the pressure at the point P one.
Furthermore, we can prove that pressure at the point P three is equal to pressure at the point P one.
This creates a problem, which is the lack of pressure gradient between points P one and P three.
This is because Bernoulli.s equation is driven by assuming inviscid uncompressible flow by using only conservation of energy and conservation of mass.
However, in nature there is not such a thing as inviscid and uncompressible flow.
If we take into account viscosity alone however, we end up with very complex equations.
The simplicity of the Bernoulli equation allows us to calculate the flow speed in the pipes by just measuring the pressure drop in converging diverging nozzles. With the use of U-tube manometers shown here we can measure pressure difference between point P three and point P two. This pressure difference will be also equal to pressure difference in between point P one and point P two. From here we can calculate the flow rate of fluid flowing in the pipe. Notice how the pressure differs between the two points when we increase the flow speed or vice versa.
Clemens Hershel was the first man to put the Venturi principle in his flow meter invention. He named his invention the Venturi Meter out of respect to Venturi.s seventeen hundred ninety seven experiments on the subject. If he named his invention the Hershel Meter, Venturi.s name would be a small footnote in scientific books, we should be thankful to Clemens Hershel.s for his modesty. Hershel was awarded the Herriot-Cresson Gold Medal of the Franklin Institute of Pennsylvania for his Venturi Meter in eighteen hundred eighty nine. By using this flow meter you can measure the flow rate passing from very small tubes to very large pipes. Indeed millions of Venturi flow meters small and large are being used all over the world. Devices made by using Venturi.s principles are extremely reliable, because they have no moving parts, are extremely simple and very useful for so many applications. Flow meters, carburetors, steam injectors, sprays are few examples of many.