VENTURI TUBE
BERNOULLI’S EQUATION
Venturi tube
The Venturi effect, published in 1797 by Giovanni Venturi, applies Bernoulli's principle to a fluid that flows
through a tube with a constriction in it, such as in figure 2. The Venturi tube provides a handy method for
mixing fluids or gases, and is popular in carburetors and atomizers, which use the low pressure region
generated at the constriction to pull the liquid into the gas flow. It also offers a particularly clear example of
the Bernoulli principle.
As the fluid flows through the constriction, the fluid molecules speed up, as indicated by the animation in the
figure. The molecules must speed up in the constricted region in order for the total flow rate to remain the
same. However many molecules enter the tube in a given time must be the same as the number of molecules
going through the constriction and coming out the other end. What goes in must come out. Since the cross
section is smaller in the constriction, the molecules must move faster in order for enough molecules to get
through in the specified time.
Since the molecules are flowing faster in the constriction, Bernoulli's principle indicates that the pressure in
the constriction should be lower than it is outside. Indeed, in order for the molecules to speed up as they
enter the constriction, and then slow down again as they leave, there must be a pressure difference at the
entrance and exit of the constriction. High pressure before the constriction accelerates molecules into the low
pressure region of the constriction, and high pressure after the constriction slows them down again as they
exit.
Venturi tube
Venturi tube
Venturi tube
Venturi tube
Venturi tube