A venturi can also be used to mix a fluid with air. If a pump forces the fluid through a tube connected to a system consisting 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, and at the end of the system a mixture of fluid and air will appear. To avoid undue drag, a venturi typically has an entry cone of 30 degrees and an exit cone of 5 degrees. Named after Giovanni Battista Venturi (1746–1822), Italian physicist.