Hydraulics is the science that studies the motion and use of liquids, particularly water; in fact, the word “hydraulic” comes from the Greek word ὑδραυλικός (hydraulikos) derived from ὕδραυλος meaning “hydraulo”, composed of ὑδρ- (hydr-) which is a contraction of ὕδωρ (hydor) meaning “water”, and αυλός (aulos) meaning “pipe”.
The theoretical basis of hydraulics is provided by the laws of fluid mechanics, especially those of hydrostatics and hydrodynamics. However, it should be noted that the phenomena studied by hydraulics can not always be schematized in a simple way, so as to allow a mathematical treatment: hydraulics is therefore a discipline with a decidedly experimental character, in which many phenomena are represented by empirical laws. The development of hydraulics is linked to a series of practical applications, such as those relating to the supply of water (aqueducts, irrigation systems), the exploitation of water for energy production (hydroelectric plants, hydraulic machinery), the creation of works (dams, embankments, canals, etc..) with the aim of regulating or modifying the flow of water in a given region.
The peoples of Mesopotamia and Egypt and above all the Chinese realized hydraulic works of great commitment; remarkable were the results obtained by the Greeks, in particular in the Alexandrian period, both in the theoretical field, with the foundation of hydrostatics by Archimedes, and in the practical one, with the construction of complex hydraulic machines, such as the cochlea, attributed to Archimedes himself, the suction and pressure pump attributed to Ctesibio, the fountain of Erone, the water wheel, etc. Interesting hydraulic works are also due to the Etruscans, for example the drainage canals of the Po river, in Italy. A very advanced technique was that of the Romans, who built great aqueducts; we owe to Frontino, curator aquarum of Nero, a treatise on hydraulics, dedicated mainly to aqueducts, in which some problems are also considered from a theoretical point of view.
During the Middle Ages hydraulics, although there had been an accumulation of small practical advances, was based on the heritage of Roman theoretical knowledge and the development that this discipline had in the East, especially in China. A great impulse, which interested hydraulics also in the theoretical field, took place during the Renaissance, in Italy, and later in France and England, with Leonardo da Vinci, S. Stevin, G. Galilei, E. Torricelli, I. Newton, B. Pascal, D. Bernoulli, etc., to whom we owe a first theoretical arrangement of hydrostatics and hydrodynamics. Finally, in the eighteenth and nineteenth centuries, modern hydraulics was developed, based mainly on systematic experimental surveys, by A. de Chézy, G. Bidone, H. Ph. Darcy, H. E. Bazin, O. Reynolds, etc..