Head

As the units for all the various forms of energy in the equation,

are measured in units of distance, such terms are at times termed to as "heads" (velocity head, pressure head, & elevation head). The term head is generally used by engineers in reference to pressure. It is a reference to the height, usually in feet, of a column of water which a given pressure will sustain. Each of the energies possessed by a fluid can be stated in terms of head. The elevation head symbolizes the potential energy of a fluid due to its elevation above the reference level. The velocity head symbolizes the kinetic energy of the fluid. This is the height in feet which a flowing fluid would increase in a column when all of its kinetic energy was transformed to potential energy. The pressure head symbolizes the flow energy of a column of fluid whose weight is equal to the pressure of the fluid. The sum of the velocity head, elevation head, and pressure head of a fluid is termed as the total head. Therefore, Bernoulli's equation defines that the total head of the fluid is constant.