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Hydraulics

physical science Maturity 9-11 Next article →

Hydraulics is an applied science and a technology that focuses on the mechanical properties of liquids. It is rooted in fluid mechanics, which is the study of how fluids behave. Engineers use hydraulics to generate, control, and transmit power through the use of pressurized liquids. This field is essential to many engineering modules. It covers diverse topics such as pipe flow, dam design, and fluid control circuitry.

Hydraulics and other studies (en)
Hydraulics and other studies (en)

Hydraulics is often described as the liquid counterpart to pneumatics, which deals with gases.

The core mechanism of hydraulics relies on the behavior of pressurized fluids. When a force is applied to a liquid in a confined space, it creates pressure. A vital principle in this process is Pascal's law. This law states that for an incompressible fluid at rest, any change in pressure applied at one point is transmitted undiminished throughout the entire fluid. This means that an increase in pressure at one end of a container results in an equal increase at every other end. This principle allows for the creation of a hydraulic press. Such a machine can take a small force acting on a small area and multiply it into a much larger force acting over a larger area.

Table of Hydraulics and Hydrostatics, Cyclopaedia, Volume 1
Table of Hydraulics and Hydrostatics, Cyclopaedia, Volume 1

Hydraulic studies are often divided into different branches based on how the liquid moves. One major branch is free surface hydraulics. This field deals with flow where the liquid has a surface exposed to the air. Common examples include the flow in rivers, canals, lakes, estuaries, and seas. A specific sub-field of this is open-channel flow. This sub-field focuses specifically on the movement of liquids within open channels.

Open Channel
Open Channel

In contrast, other applications focus on fluid power within closed systems to move machinery.

Humans have utilized hydraulic principles since ancient times to manage water and energy. In Mesopotamia and ancient Egypt, irrigation and water clocks were used as early as the 6th and 2nd millennia BC. The Maya at Palenque engineered a pressurized water system in the Americas. They built a subterranean aqueduct that narrowed at the downstream end. This design created enough pressure to shoot water upwards to a height of 6 meters. In Persia, the Shushtar Historical Hydraulic System used canals and dams. This system was started by King Darius the Great and finished by Roman engineers. UNESCO has called this work a masterpiece of creative genius.

History also shows remarkable hydraulic achievements in other parts of the world. In ancient Sri Lanka, engineers used valve towers, called Bisokotuwa, to regulate water escape. They built massive reservoirs like Kalawewa and Parakrama Samudra. In China, Du Shi used a waterwheel to power blast furnace bellows. Zhang Heng used hydraulics to rotate an armillary sphere for astronomy. The Roman Empire utilized siphons to move water across valleys. They also practiced hydraulic mining in places like Las Medulas in Spain. At this site, at least seven long aqueducts were used to erode soft deposits and extract gold.

Segovia Aqueduct
Segovia Aqueduct

During the Islamic Golden Age, hydraulic technology reached new levels of complexity. Engineers built various water-powered industrial mills, such as paper, steel, and sugar mills. By the 11th century, these mills were operating in every province of the Islamic world. The inventor Al-Jazari described many water-powered devices in his book. He even designed programmable automata, or robots, in 1206. These included musicians that could play different rhythms using a programmable drum machine. This era showed how water could be used to create early forms of automated control.

Modern hydraulic science was shaped by many important researchers and inventors. In the 16th century, Giuseppe Ceredi improved the Archimedean screw pump for irrigation. In 1619, Benedetto Castelli published work that helped found modern hydrodynamics. Later, Blaise Pascal's studies on hydrostatics led to the invention of the hydraulic press. In the 19th century, cities built hydraulic power networks to operate lifts and cranes. The French physician Poiseuille also contributed by researching how blood flows through the body. He discovered a law regarding how the diameter of a tube affects the rate of flow.

Tuebingen-gerstenmuehle
Tuebingen-gerstenmuehle

Today, hydraulics remains connected to many different scientific fields and biological systems. It is not just for machines; it is also found in the human body. The principles of hydraulics are at work within the vascular system and erectile tissue. This shows that the way we move machines is similar to how nature moves fluids. From the massive dams that hold back rivers to the tiny vessels in our veins, hydraulics is a fundamental part of how the world works.

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Hydraulics and other studies (en).svg
File:Open Channel.png
Open Channel.png
File:Table of Hydraulics and Hydrostatics, Cyclopaedia, Volume 1.jpg
Table of Hydraulics and Hydrostatics,...
File:Tuebingen-gerstenmuehle.jpg
Tuebingen-gerstenmuehle.jpg
File:Sigiriya moat and garden2.jpg
Sigiriya moat and garden2.jpg
File:Segovia Aqueduct.JPG
Segovia Aqueduct.JPG
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