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Pressure as a function of the height above the sea level. There are two equations for computing pressure as a function of height. The first equation is applicable to the atmospheric layers in which the temperature is assumed to vary with altitude at a non null lapse rate of : = [,, ()] ′, The second equation is applicable to the atmospheric layers in which the temperature is assumed not to ...
[1] [2] By the barometric formula, 1 bar is roughly the atmospheric pressure on Earth at an altitude of 111 metres at 15 °C. The bar and the millibar were introduced by the Norwegian meteorologist Vilhelm Bjerknes, who was a founder of the modern practice of weather forecasting, with the bar defined as one mega dyne per square centimeter. [3]
For instance, an absolute pressure of 80 kPa may be described as a gauge pressure of −21 kPa (i.e., 21 kPa below an atmospheric pressure of 101 kPa). For example, abdominal decompression is an obstetric procedure during which negative gauge pressure is applied intermittently to a pregnant woman's abdomen. Negative absolute pressures are possible.
Moderate vacuum pressure readings can be ambiguous without the proper context, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 4 inHg, calculated as 30 inHg (typical atmospheric pressure) − 26 inHg (gauge pressure).
Flux F through a surface, dS is the differential vector area element, n is the unit normal to the surface. Left: No flux passes in the surface, the maximum amount flows normal to the surface.
In fluid mechanics, pressure head is the height of a liquid column that corresponds to a particular pressure exerted by the liquid column on the base of its container. It may also be called static pressure head or simply static head (but not static head pressure). Mathematically this is expressed as:
Air pressure in an automobile tire relative to atmosphere (gauge pressure) [citation needed] +210 to +900 kPa +30 to +130 psi Air pressure in a bicycle tire relative to atmosphere (gauge pressure) [57] 300 kPa 50 psi Water pressure of a garden hose [58] 300 to 700 kPa 50–100 psi Typical water pressure of a municipal water supply in the US [59]
Aircraft Mode “C” transponders report the pressure altitude to air traffic control; corrections for atmospheric pressure variations are applied by the recipient of the data. The relationship between static pressure and pressure altitude is defined in terms of properties of the ISA.