Bernoulli’s Theorem

The Bernoulli Theorem1 is a mathematical derivation based on the law of conservation of energy. This theorem states that the total energy of a fluid at any particular point above a datum plane is the sum of the elevation head, the pressure head, and the velocity head. Stated mathematically:

    Eq. (1)

If there are no friction losses and no energy is added to or taken from the system, H is constant for any point in the fluid. In reality, whenever fluid is moving there is friction loss (h_L). This loss describes the difference in total energy at two points in the system. Expressing the energy levels at Point 1 versus Point 2 then becomes:

 Eq. (2)

All practical formulas for fluid flow are derived from the above. Modifications to Eq (2) have been proposed by many investigators to account for the friction losses.