Fluid pressure is the pressure on an object submerged in a fluid, such as water. The pressure can be provided from a number of sources: Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... A subset of the phases of matter, fluids include liquids, gases, plasmas and, to some extent, plastic solids. ...

1. the sheer weight of the fluid, such as in scuba diving, when the diver goes deeper into the water, the water pressure increases; or in the earth's atmosphere, as a plane goes higher, the air pressure decreases;
2. a pump, such as when water "pumped" into a water tower; or
3. a compressor, such as in a small water supply system in a rural well for a house connected to an air compressor. Water pressure is used in our daily lives to control the flow of water coming from any mechanical water source.

Fluid pressure occurs in one of two situations:

1. an open condition, such as the ocean, or a swimming pool, or
2. a closed condition, such as a water line or a gas line.

Open conditions are considered to be "static" or not moving (even in the ocean where there are waves and currents) because the fluid is essentially "at rest." The pressure in open conditions conform with principles of fluid statics. Fluid statics (also called hydrostatics) is the science of fluids at rest, and is a sub-field within fluid mechanics. ...

Closed bodies of fluid are either "static," when the fluid is not moving, or "dynamic," when the fluid is moving, like through a pipe. The pressure in closed conditions conform with the principles of fluid dynamics. Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ...

The concepts of fluid pressure are predominantly attributed to the discoveries of Blaise Pascal and Daniel Bernoulli. These concepts are given in greater detail in the remainder of this article. Blaise Pascal (June 19, 1623–August 19, 1662) was a French mathematician, physicist, and religious philosopher. ... Daniel Bernoulli Daniel Bernoulli (Groningen, February 8, 1700 – Basel, March 17, 1782) was a Dutch-born mathematician who spent much of his life in Basel, Switzerland. ...

Concepts of fluid pressure

There are two components to pressure: force and area. The more force, the larger the pressure; the more area, the smaller the pressure. As such, the force on an object in contact with fluid depends on three factors (as summarized in Bernoulli's equation): Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... In physics, a force is defined as the rate of change of momentum of that body. ... Area is a physical quantity expressing the size of a part of a surface. ... In fluid dynamics, Bernoullis equation, derived by Daniel Bernoulli, describes the behavior of a fluid moving along a streamline. ...

1. Is the fluid at rest or moving? If moving, how fast and in what direction in relation to the object?
2. What is the vertical distance from the surface of the fluid (if a liquid) to the object?
3. Are there any sources of pressure, such as from a pump or compressor?

Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... Manual water pump in Košice-Ťahanovce, Slovakia An electric driven pump of water works nearby the Hengstey See, Germany 19th century Dutch diesel pump in Rijswijk, Netherlands Manual pump used to obtain water in Afghanistan This article is about the mechanical device. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ...

Hydrostatic pressure

In the case where the fluid is at rest, called fluid statics or hydrostatics (from hydro meaning "water" and static meaning "at rest"), the force acting on the object is the sheer weight of the fluid above, up to the water's surface—such as from a water tower. The resulting hydrostatic pressure (static pressure) is isotropic: the pressure acts in all directions equally, according to Pascal's law: Fluid statics (also called hydrostatics) is the science of fluids at rest, and is a sub-field within fluid mechanics. ... Hydrostatics, also known as fluid statics, is the study of fluids at rest. ... The mushroom-shaped concrete water tower of Roihuvuori in Helsinki, Finland was built in the 1970s. ... Static pressure is a term used in ventilation engineering, airspeed indication, fluid statics, hydraulics and flow measurement. ... Isotropic means independent of direction. Isotropic radiation has the same intensity regardless of the direction of measurement, and an isotropic field exerts the same action regardless of how the test particle is oriented. ... In the physical sciences, Pascals law or Pascals principle gives the fluid pressure at mechanical equilibrium (see also fluid statics), on which only gravity forces are taken into account. ...

where:

• ρ (rho) is the density of the fluid (the practical density of fresh water is 1000 kg/m³);
• g is the acceleration due to gravity (practical value 9.81 m/s² );
• h is the height of the water column in meters.

In the following example. Assume a column 1 meter high, the pressure on the floor of the column will be as follow: 1. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... The acceleration due to gravity denoted g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... The metre, or meter (symbol: m) is the SI base unit of length. ...

Pa.

The pressure increases linearly with the water depth. The pascal (symbol: Pa) is the SI unit of pressure. ... The word linear comes from the Latin word linearis, which means created by lines. ...

Fluid dynamic pressure

Next, when the fluid is moving in a pipe, called fluid dynamics or hydrodynamics (dynamics meaning "moving" or "changing"), the interaction of the fluid with the walls of the pipe creates friction and energy loss. In fluid dynamics, the fluid pressure is anisotropic (not isotropic), i.e. the pressure is not the same in all directions. The anisotrophy is mainly caused by the friction losses, so the further an object is away from the surface of the fluid (assuming the fluid is moving from the fluid surface to the object), the less pressure there will be on that object in the fluid. (Note: There are other reasons for the anisotrophy that are beyond the scope of this article.) These concepts are mathematically explained by Bernoulli's equation, and are applicable to all fluids. Fluid dynamics is the subdiscipline of fluid mechanics that studies fluids (liquids and gases) in motion. ... The word dynamics can refer to: in physics, a branch of mechanics; see dynamics (mechanics). ... Look up anisotropy in Wiktionary, the free dictionary. ... In fluid dynamics, Bernoullis equation, derived by Daniel Bernoulli, describes the behavior of a fluid moving along a streamline. ...

Consider this simplified example: assume a 10 m high water tower with a large reservoir, that would give us a static pressure of 100,000 Pa (100 kPa or 100,000 N/m² at ground level. Now connect a 100-meter long horizontal pipe to the bottom of the column. From experiment it is known that the friction loss in this typical pipe, depending on material and diameter, is 100 Pa per meter of pipe length. So for the 100 meter pipe, that would be 10 kPa of pressure loss. So the pressure at the end of our pipe would be 100 kPa - 10 kPa = 90 kPa. The mushroom-shaped concrete water tower of Roihuvuori in Helsinki, Finland was built in the 1970s. ... Static pressure is a term used in ventilation engineering, airspeed indication, fluid statics, hydraulics and flow measurement. ... The newton (symbol: N) is the SI unit of force. ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ...

Applications

• Artesian well
• Blood pressure
• Plant cell stability

Geological strata giving rise to an Artesian well An artesian aquifer is an aquifer whose water is overpressurized. ... Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. ...

See also

• Fluid statics
• Hydraulics