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In fluid dynamics, dynamic pressure (denoted by q or Q and sometimes called velocity pressure) is the quantity defined by: [1] where (in SI units): u is the flow speed in m/s. It can be thought of as the fluid's kinetic energy per unit volume. For incompressible flow, the dynamic pressure of a fluid is the difference between its total pressure ...
Atmospheric pressure, also known as air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101,325 Pa (1,013.25 hPa ), which is equivalent to 1,013.25 millibars , [ 1 ] 760 mm Hg , 29.9212 inches Hg , or 14.696 psi . [ 2 ]
The International Standard Atmosphere (ISA) is a static atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes ...
Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 5 Pa (100 kPa, 1 bar). NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). [ 3 ] This standard is also called normal temperature and pressure (abbreviated as NTP).
The value of subscript b ranges from 0 to 6 in accordance with each of seven successive layers of the atmosphere shown in the table below. The reference value for ρ b for b = 0 is the defined sea level value, ρ 0 = 1.2250 kg/m 3 or 0.0023768908 slug/ft 3 .
US customary units. 14.69595 psi. other metric units. 1.013250 bar. Aneroid barometer for household use from c. 1925. The standard atmosphere (symbol: atm) is a unit of pressure defined as 101 325 Pa. It is sometimes used as a reference pressure or standard pressure. It is approximately equal to Earth 's average atmospheric pressure at sea level.
Pressure may also be expressed in terms of standard atmospheric pressure; the unit atmosphere (atm) is equal to this pressure, and the torr is defined as 1 ⁄ 760 of this. Manometric units such as the centimetre of water , millimetre of mercury , and inch of mercury are used to express pressures in terms of the height of column of a particular ...
Orders of magnitude (pressure) This is a tabulated listing of the orders of magnitude in relation to pressure expressed in pascals. psi values, prefixed with + and -, denote values relative to Earth's sea level standard atmospheric pressure (psig); otherwise, psia is assumed. Magnitude. Pressure. lbf/in 2 or dB.