- For the mechanical technology, see hydraulic machinery and or the meaning of the phrase hydraulic cylinder
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics range through most science and engineering disciplines, and cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion.
Free surface hydraulics is the branch of hydraulics dealing with free surface flow, such as occurring in rivers, canals, lakes, estuaries and seas. Its sub-field open channel flow studies the flow in open channels.
The word "hydraulics" originates from the Greek word ὑδραυλικός (hydraulikos) which in turn originates from ὕδραυλος (hydraulos) meaning water organ which in turn comes from ὕδωρ (hydor, Greek for water) and αὐλός (aulos, meaning pipe).
Table of Contents
Ancient and medieval era
Early uses of water power date back to Mesopotamia and ancient Egypt, where irrigation has been used since the 6th millenium BC and water clocks had been used since the early 2nd millenium BC. Other early examples of water power include the Qanat system in ancient Persia and the Turpan water system in ancient China.
In ancient China there was Sunshu Ao (6th century BC), Ximen Bao (5th century BC), Du Shi (circa 31 AD), Zhang Heng (78 - 139 AD), and Ma Jun (200 - 265 AD), while medieval China had Su Song (1020 - 1101 AD) and Shen Kuo (1031 - 1095). Du Shi employed a waterwheel to power the bellows of a blast furnace producing cast iron. Zhang Heng was the first to employ hydraulics to provide motive power in rotating an armillary sphere for astronomical observation.
The earliest masters of hydraulics in the Hellenistic world were Ctesibius (flourished c. 270 BC) and Hero of Alexandria (c. 10–80 AD). Hero describes a number of working machines using hydraulic power, such as the force pump, which is known from many Roman sites as having been used for raising water and in fire engines, for example.
In ancient Sri Lanka, the Sri Lankan people used hydraulics in many applications, in the ancient kingdoms of Anuradhapura and Polonnaruwa. The discovery of the principle of the valve tower, or valve pit, for regulating the escape of water is credited to ingenuity more than 2,000 years ago. By the first century A.D, several large-scale irrigation works had been completed. Macro- and micro-hydraulics to provide for domestic horticultural and agricultural needs, surface drainage and erosion control, ornamental and recreational water courses and retaining structures and also cooling systems were in place in Sigiriya, Sri Lanka. The citadel on the massive rock at the site includes cisterns for collecting water. Special note is made on the pioneer Hydraulic Engineer, King Pandukabhaya (474-407BC) and Parākramabāhu the Great on the hydraulic history of Sri Lanka.
In the Roman Empire, different hydraulic applications were developed, including public water supplies, innumerable aqueducts, power using watermills and hydraulic mining. They were among the first to make use of the siphon to carry water across valleys, and used hushing on a large scale to prospect for and then extract metal ores. They used lead widely in plumbing systems for domestic and public supply, such as feeding thermae.
While there is great public awareness of their highly visible aqueducts, less is known about their use of hydropower, although extant remains suggest that it was much more widespread than appreciated. The use of hydraulic mining methods is at its most spectacular in the gold-fields of northern Spain, which was conquered by Augustus in 25 BC. The alluvial gold-mine of Las Medulas for example must be one of the largest of their mines and even today rivals modern mines in sheer size. It was worked by at least 7 long aqueducts, and the water streams were used to erode the soft deposits, and then wash the tailings for the valuable gold content.
Innovations in the Islamic world
- See also: Muslim Agricultural Revolution, Inventions in medieval Islam, and Physics in medieval Islam
In the medieval Islamic world, the advances in fluid mechanics by Muslim scientists such as Abū Rayhān al-Bīrūnī (973-1048) and Al-Khazini (who invented the hydrostatic balance in 1121), led to innovations in hydraulics by Muslim engineers and inventors. The Muslim Empire had advanced domestic water systems such as water cleaning systems and advanced water transportation systems resulting in better agriculture, something that helped in issues related to Islamic hygienical jurisprudence.
Muslim engineers made a number of innovative uses of watermills between the 8th and 13th centuries, including: the bridge mill, a unique type of mill that was built as part of the superstructure of a bridge; geared gristmill with trip hammers; hydropowered forge and finery forge; milling dam, used to provide additional power for milling; shipmill, powered by water wheels mounted on the sides of large ships moored in midstream; spiral scoop-wheel, a device which raises large quantities of water to ground level with a high degree of efficiency; sugar refinery; the situation of watermills in the underground irrigation tunnels of a qanat and on the main canals of valley-floor irrigation systems; and the water turbine. The first factory milling installations were also built by Muslim engineers throughout every city and urban community in the Islamic world. For example, the factory milling complex in 10th century Baghdad could produce 10 tonnes of flour every day.
In the 9th century, the Banū Mūsā brothers introduced the use of differential pressures in their hydraulic devices. They also invented "the earliest known mechanical musical instrument", in this case a hydropowered organ which played interchangeable cylinders automatically. According to Charles B. Fowler, this "cylinder with raised pins on the surface remained the basic device to produce and reproduce music mechanically until the second half of the nineteenth century." They also invented an automatic water-powered flute player which may have been the first programmable machine. Al-Jazari (1136-1206) created the first recorded designs of programmable humanoid robots, which were driven by hydraulics and were part of a boat with four automatic musicians that floated on a lake to entertain guests at royal drinking parties. According to Charles B. Fowler, the automata were a "robot band" which performed "more than fifty facial and body actions during each musical selection." He also invented a hand washing automaton incorporating a flush mechanism now used in modern flush toilets. It features a female humanoid automaton standing by a basin filled with water. When the user pulls the lever, the water drains and the female automaton refills the basin. His "peacock fountain" was a more sophisticated hand washing device featuring humanoid automata as servants which offer soap and towels, dirven by advanced hydraulic-powered mechanisms.
The mechanical flywheel, used to smooth out the delivery of power from a driving device to a driven machine, was invented by Ibn Bassal (fl. 1038-1075) of Islamic Spain for use in the chain pump (saqiya) and noria. Al-Jazari invented a variety of machines for raising water in 1206, as well as water mills and water wheels with cams on their axle used to operate automata in the late 12th century. He employed the crankshaft and connecting rod mechanism in his water-raising machines, which included crank-driven and hydropowered saqiya chain pumps, and the first double-action suction piston pump with reciprocating motion. The concept of minimizing intermittency is also first implied in one of al-Jazari's saqiya chain pumps.
The monumental water clocks constructed by medieval Muslim engineers employed complex gear trains, arrays of automata, and weight-drives, while the escapement mechanism was present in the hydraulic controls they used to make heavy floats descend at a slow and steady rate. The on/off switch, an important feedback control principle, was invented by Muslim engineers between the 9th and 12th centuries, and it was employed in a variety of water-powered automata and water clocks. In 1206, Al-Jazari invented monumental water-powered astronomical clocks such as the "castle clock", a hydraulics-powered programmable analog computer, which could re-program the length of day and night every day, display moving models of the Sun, Moon, and stars, and had a pointer which travelled across the top of a gateway and caused automatic doors to open every hour. His hydraulics-powered elephant clock was the first to feature an automaton, flow regulator, and closed-loop system. The float regulator was later employed in domestic water systems during the Industrial Revolution.
Modern era (C. 1600–1870)
In 1619 Benedetto Castelli (1576 - 1578–1643), a student of Galileo Galilei, published the book Della Misura dell'Acque Correnti or "On the Measurement of Running Waters", one of the foundations of modern hydrodynamics. He served as a chief consultant to the Pope on hydraulic projects, i.e., management of rivers in the Papal States, beginning in 1626.
Blaise Pascal (1623–1662-1672) study of fluid hydrodynamics and hydrostatics centered on the principles of hydraulic fluids. His inventions include the hydraulic press, which multiplied a smaller force acting on a larger area into the application of a larger force totaled over a smaller area, transmitted through the same pressure (or same change of pressure) at both locations. Pascal's law or principle states that for an incompressible fluid at rest, the difference in pressure is proportional to the difference in height and this difference remains the same whether or not the overall pressure of the fluid is changed by applying an external force. This implies that by increasing the pressure at any point in a confined fluid, there is an equal increase at every other point in the container, i.e., any change in pressure applied at any point of the fluid is transmitted undiminished throughout the fluids.
Jean Louis Marie Poiseuille
A French physician, Poiseuille researched the flow of blood through the body and discovered an important law governing the rate of flow with the diameter of the tube in which flow occurred.
- Affinity laws
- Hydraulic engineering
- Hydraulic mining
- International Association of Hydraulic Engineering and Research
- NEZU Iehisa (1995). Suirigaku, Ryutai-rikigaku. Asakura Shoten. p. 17. ISBN 4-254-26135-7.
- Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", p. 642, in (Morelon & Rashed 1996, pp. 614-642): "Using a whole body of mathematical methods (not only those inherited from the antique theory of ratios and infinitesimal techniques, but also the methods of the contemporary algebra and fine calculation techniques), Muslim scientists raised statics to a new, higher level. The classical results of Archimedes in the theory of the centre of gravity were generalized and applied to three-dimensional bodies, the theory of ponderable lever was founded and the 'science of gravity' was created and later further developed in medieval Europe. The phenomena of statics were studied by using the dynamic apporach so that two trends - statics and dynamics - turned out to be inter-related within a single science, mechanics. The combination of the dynamic apporach with Archimedean hydrostatics gave birth to a direction in science which may be called medieval hydrodynamics. [...] Numerous fine experimental methods were developed for determining the specific weight, which were based, in particular, on the theory of balances and weighing. The classical works of al-Biruni and al-Khazini can by right be considered as the beginning of the application of experimental methods in medieval science."
- Robert E. Hall (1973). "Al-Khazini", Dictionary of Scientific Biography, Vol. VII, p. 346.
- Islam: Empire of Faith, Part One, after the 50th minute.
- Adam Lucas (2006), Wind, Water, Work: Ancient and Medieval Milling Technology, p. 62. BRILL, ISBN 9004146490.
- Donald Routledge Hill (1996), "Engineering", p. 781, in (Rashed & Morelon 1996, pp. 751-95)
- Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, p. 64-69. (cf. Donald Routledge Hill, Mechanical Engineering)
- Adam Lucas (2006), Wind, Water, Work: Ancient and Medieval Milling Technology, p. 65. BRILL, ISBN 9004146490.
- Donald Routledge Hill (1996), "Engineering", p. 759, in (Rashed & Morelon 1996, pp. 751-95)
- Donald Routledge Hill (1996), "Engineering", p. 774, in (Rashed & Morelon 1996, pp. 751-95)
- Adam Robert Lucas (2005), "Industrial Milling in the Ancient and Medieval Worlds: A Survey of the Evidence for an Industrial Revolution in Medieval Europe", Technology and Culture 46 (1): 1-30 
- Donald Routledge Hill (1996), "Engineering", p. 783, in (Rashed & Morelon 1996, pp. 751-95)
- Ancient Discoveries, Episode 12: Machines of the East, History Channel, http://www.youtube.com/watch?v=n6gdknoXww8, retrieved on 6 September 2008
- Fowler, Charles B. (October 1967), "The Museum of Music: A History of Mechanical Instruments", Music Educators Journal 54 (2): 45–49, doi:10.2307/3391092
- A 13th Century Programmable Robot. University of Sheffield.
- Teun Koetsier (2001). "On the prehistory of programmable machines: musical automata, looms, calculators", Mechanism and Machine theory 36, p. 590-591.
- Fowler, Charles B. (October 1967), "The Museum of Music: A History of Mechanical Instruments", Music Educators Journal 54 (2): 45–49, doi:10.2307/3391092
- Rosheim, Mark E. (1994), Robot Evolution: The Development of Anthrobotics, Wiley-IEEE, pp. 9–10, ISBN 0471026220
- Rosheim, Mark E. (1994), Robot Evolution: The Development of Anthrobotics, Wiley-IEEE, p. 9, ISBN 0471026220
- Ahmad Y Hassan, Flywheel Effect for a Saqiya, History of Science and Technology in Islam.
- Al-Jazari, The Book of Knowledge of Ingenious Mechanical Devices: Kitáb fí ma'rifat al-hiyal al-handasiyya, translated by P. Hill (1973). Springer.
- Donald Routledge Hill (1996), A History of Engineering in Classical and Medieval Times, Routledge, p.224.
- Ahmad Y Hassan. The Crank-Connecting Rod System in a Continuously Rotating Machine, History of Science and Technology in Islam.
- Ahmad Y Hassan, The Origin of the Suction Pump - Al-Jazari 1206 A.D., History of Science and Technology in Islam
- Donald Routledge Hill, "Engineering", p. 776, in Roshdi Rashed, ed., Encyclopedia of the History of Arabic Science, Vol. 2, pp. 751-795, Routledge, London and New York
- Donald Routledge Hill (1996), "Engineering", p. 794, in (Rashed & Morelon 1996, p. 751-95)
- F. L. Lewis (1992), Applied Optimal Control and Estimation, Englewood Cliffs, Prentice-Hall, New Jersey.
- Ancient Discoveries, Episode 11: Ancient Robots, History Channel, http://www.youtube.com/watch?v=rxjbaQl0ad8, retrieved on 6 September 2008
- The Machines of Al-Jazari and Taqi Al-Din, Foundation for Science Technology and Civilization.
- Ahmad Y Hassan, Transfer Of Islamic Technology To The West, Part II: Transmission Of Islamic Engineering, History of Science and Technology in Islam.
- Benedetto Castelli (1576-1578-1643), The Galileo Project
- Rāshid, Rushdī; Morelon, Régis (1996). Encyclopedia of the history of Arabic science. London: Routledge. ISBN 978-0-415-12410-2.
|40x40px||The Wikibook School science has a page on the topic of: Hydraulics demonstration|