As originally formulated, a statement of the conservation of energy (per unit mass) for an inviscid fluid in steady motion.

The specific energy is composed of the kinetic energy (1/2)v², where v is the speed of the fluid; the potential energy gz, where g is the acceleration of gravity and z the height above an arbitrary reference level; and the work done by the pressure forces ∫ αdp, where p is the pressure, α the specific volume, and the integration is always with respect to values of p and α on the same parcel. Thus, the relationship