This principle is a simplification of Bernoulli's equation, which states that the sum of all forms of energy in a fluid flowing along an enclosed path (a streamline) is the same at any two points in that path. It is named after the Dutch/Swiss mathematician/scientist Daniel Bernoulli, though it was previously understood by Leonhard Euler and others. In fluid flow with no viscosity, and therefore, one in which a pressure difference is the only accelerating force, the principle is equivalent to Newton's laws of motion.
Incompressible flow
The original form, for incompressible flow in a uniform gravitational field, is: [pic] where: v = fluid velocity along the streamline g = acceleration due to gravity h = height of the fluid p = pressure along the streamline ρ = density of the fluid
These assumptions must be met for the equation to apply: • Inviscid flow − viscosity (internal friction) = 0 • Steady flow • Incompressible flow − ρ = constant along a streamline. Density may vary from streamline to streamline, however. • Generally, the equation applies along a streamline. For constant-density potential flow, it applies throughout the entire flow field.
An increase in velocity and the corresponding decrease in pressure, as shown by the equation, is often called Bernoulli's principle. The equation is named for Daniel Bernoulli although it was first presented in the above form by Leonhard Euler.
A common example used to illustrate the effect of Bernoulli's principle is when air flows around an airplane wing; the velocity of the air is higher and the pressure is lower on the top surface of the wing when compared to the bottom surface. This