A venturi can be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting of
a venturi to increase the water speed (the diameter decreases), a short piece of tube with a small hole in it, and last a
venturi that decreases speed (so the pipe gets wider again), air will be sucked in through the small hole because of
changes in pressure. At the end of the system, a mixture of fluid and air will appear.
The simplest apparatus, as shown in the diagram, is a tubular setup known as a Venturi tube or simply a venturi. Fluid flows through a length of pipe of varying diameter. To avoid undue drag, a venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees.
The device works via the Venturi effect, an example of Bernoulli's principle. In the case of incompressible fluid flow through a tube or pipe with a constriction in it. The fluid velocity must increase through the constriction to satisfy the equation of continuity, while its pressure must decrease due to conservation of energy: the gain in kinetic energy is supplied by a drop in pressure or a pressure gradient force.