Fluid

The fluid mechanics called fluid ( from the Latin fluidus for " fluent " and by the English fluid for the " liquid") a substance that does not resist an arbitrarily slow shear ( finite viscosity). The overarching term fluid is used for gases and liquids, because most physical laws for both types of material are alike and many of its properties only quantitatively, ie in their magnitude, but not qualitatively different.

Real fluids are divided into Newtonian fluids can be described by the Navier -Stokes equation, and non-Newtonian fluids of complex behaving that are treated in rheology.

Under fluid management is defined as the set of services related to liquid working media.