Hydraulics (from Greek: Υδραυλική) is a technology and
applied science using engineering, chemistry, and other sciences
involving the mechanical properties and use of liquids. At a very
basic level, hydraulics is the liquid counterpart of pneumatics, which
Fluid mechanics provides the theoretical foundation
for hydraulics, which focuses on the applied engineering using the
properties of fluids. In its fluid power applications, hydraulics is
used for the generation, control, and transmission of power by the use
of pressurized liquids. Hydraulic topics range through some parts of
science and most of engineering modules, and cover concepts such as
pipe flow, dam design, fluidics and fluid control circuitry, pumps.
The principles of hydraulics are in use naturally in the human body
within the heart and the penile erection. 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
ὕδωρ (hydor, Greek for water) and αὐλός (aulos, meaning
1 Ancient and medieval era
1.1 Greek / Hellenistic age
1.3 Sri Lanka
1.4 Innovations in Ancient Rome
2 Modern era (c. 1600 – 1870)
2.1 Benedetto Castelli
2.2 Blaise Pascal
2.3 Jean Léonard Marie Poiseuille
2.4 In the UK
2.5 Hydraulic models
3 See also
6 External links
Ancient and medieval era
Early uses of water power date back to
Mesopotamia and ancient Egypt,
where irrigation has been used since the 6th millennium BC and water
clocks had been used since the early 2nd millennium BC. Other early
examples of water power include the
Qanat system in ancient Persia and
Turpan water system
Turpan water system in ancient Central Asia.
Greek / Hellenistic age
The Greeks constructed sophisticated water and hydraulic power
systems. An example is the construction by Eupalinos, under a public
contract, of a watering channel for Samos, the Tunnel of Eupalinos. An
early example of the usage of hydraulic wheel, probably the earliest
in Europe, is the Perachora wheel (3rd century BC).
The construction of the first hydraulic automata by Ctesibius
(flourished c. 270 BC) and
Hero of Alexandria
Hero of Alexandria (c. 10 – 80 AD) is
notable. 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.[citation
In ancient China there was
Sunshu Ao (6th century BC),
Ximen Bao (5th
Du Shi (circa 31 AD),
Zhang Heng (78 – 139 AD), and Ma
Jun (200 – 265 AD), while medieval China had
Su Song (1020 – 1101
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.
Moat and gardens at Sigiriya.
In ancient Sri Lanka, hydraulics were widely used in the ancient
Anuradhapura and Polonnaruwa. The discovery of the
principle of the valve tower, or valve pit, (Bisokotuwa in Sinhalese)
for regulating the escape of water is credited to ingenuity more than
2,000 years ago. By the first century AD, 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 coral on the massive rock at the
site includes cisterns for collecting water. Large ancient reservoirs
Sri Lanka are Kalawewa (King Dhatusena), Parakrama Samudra (King
Parakrama Bahu), Tisa Wewa (King Dutugamunu), Minneriya (King Mahasen)
Innovations in Ancient Rome
Aqueduct of Segovia, a 1st-century AD masterpiece.
In Ancient Rome, many 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.
Hydraulic mining was used in the gold-fields of northern Spain, which
was conquered by
Augustus in 25 BC. The alluvial gold-mine of Las
Medulas was one of the largest of their mines. 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
Modern era (c. 1600 – 1870)
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) studied 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 smaller area into the application of a larger force
totaled over a larger 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 Léonard 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.[citation
In the UK
Several cities developed citywide hydraulic power networks in the 19th
century, to operate machinery such as lifts, cranes, capstans and the
like. Joseph Bramah was an early innovator and William
Armstrong perfected the apparatus for power delivery on an
industrial scale. In London, the London Hydraulic Power Company
was a major supplier its pipes serving large parts of the West End of
London, City and the Docks, but there were schemes restricted to
single enterprises such as docks and railway goods yards.
After students understand the basic principles of hydraulics, some
teachers use a hydraulic analogy to help students learn other things.
MONIAC Computer uses water flowing through hydraulic components to
help students learn about economics.
The thermal-hydraulic analogy uses hydraulic principles to help
students learn about thermal circuits.
The electronic–hydraulic analogy uses hydraulic principles to help
students learn about electronics.
International Association for Hydro-Environment
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^ Meldrum, David R.; Burnett, Arthur L.; Dorey, Grace; Esposito,
Katherine; Ignarro, Louis J. (2014). "Erectile Hydraulics: Maximizing
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engineering collection in the Science Division of the Victoria and
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^ Bird, David. Pliny's Arrugia
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^ "William George Armstrong, Baron Armstrong of Cragside (1810-1900)".
Victorianweb.org. 2005-12-22. Retrieved 2014-04-08.
^ "Subterranea Britannica: Sites: Hydraulic power in London".
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Rāshid, Rushdī; Morelon, Régis (1996), Encyclopedia of the history
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Wikimedia Commons has media related to Hydraulics.
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Basic hydraulic equations
MIT hydraulics course notes