Since the units for all the different forms of energy in
Equation 311 are measured in units ofdistance,
these terms are sometimes referred to as "heads" (pressure head,
velocity head, andelevation head). The term
head is used by engineers in reference to pressure. It is a reference
to the height, typically in feet, of a column of
water that a given pressure will support. Each ofthe
energies possessed by a fluid can be expressed in terms of head. The elevation
headrepresents the potential energy of a
fluid due to its elevation above a reference level. Thevelocity
head represents the kinetic energy of the fluid. It is the height in feet that a
flowingfluid would rise in a column if all
of its kinetic energy were converted to potential energy. Thepressure
head represents the flow energy of a column of fluid whose weight is equivalent
to thepressure of the fluid. The sum of the elevation head, velocity head, and pressure head
of a fluid is called the totalhead. Thus,
Bernoullis equation states that the total head of the fluid is constant.
