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  2. Perm (unit) - Wikipedia

    en.wikipedia.org/wiki/Perm_(unit)

    A variant of the metric perm is used in DIN Standard 53122, where permeance is also expressed in grams per square meter per day, but at a fixed, "standard" vapor-pressure difference of 17.918 mmHg. This unit is thus 17.918 times smaller than a metric perm, corresponding to about 0.084683 of a U.S. perm.

  3. Comparison of the imperial and US customary measurement ...

    en.wikipedia.org/wiki/Comparison_of_the_imperial...

    In 1824, these units were replaced with a single system based on the imperial gallon. [a] Originally defined as the volume of 10 pounds (4.54 kg) of distilled water (under certain conditions), [b] then redefined by the Weights and Measures Act 1985 to be exactly 4.546 09 L (277.4 cu in), the imperial gallon is close in size to the old ale gallon.

  4. Pressure - Wikipedia

    en.wikipedia.org/wiki/Pressure

    The average water pressure acting against a dam depends on the average depth of the water and not on the volume of water held back. For example, a wide but shallow lake with a depth of 3 m (10 ft) exerts only half the average pressure that a small 6 m (20 ft) deep pond does.

  5. Litre - Wikipedia

    en.wikipedia.org/wiki/Litre

    A litre is a cubic decimetre, which is the volume of a cube 10 centimetres × 10 centimetres × 10 centimetres (1 L ≡ 1 dm 3 ≡ 1000 cm 3). Hence 1 L ≡ 0.001 m 3 ≡ 1000 cm 3; and 1 m 3 (i.e. a cubic metre, which is the SI unit for volume) is exactly 1000 L. From 1901 to 1964, the litre was defined as the volume of one kilogram of pure ...

  6. Pressure coefficient - Wikipedia

    en.wikipedia.org/wiki/Pressure_coefficient

    This pressure distribution is simply the pressure at all points around an airfoil. Typically, graphs of these distributions are drawn so that negative numbers are higher on the graph, as the C p {\displaystyle C_{p}} for the upper surface of the airfoil will usually be farther below zero and will hence be the top line on the graph.

  7. Volume - Wikipedia

    en.wikipedia.org/wiki/Volume

    Some SI units of volume to scale and approximate corresponding mass of water. To ease calculations, a unit of volume is equal to the volume occupied by a unit cube (with a side length of one). Because the volume occupies three dimensions, if the metre (m) is chosen as a unit of length, the corresponding unit of volume is the cubic metre (m 3).

  8. Dimensionless numbers in fluid mechanics - Wikipedia

    en.wikipedia.org/wiki/Dimensionless_numbers_in...

    Dimensionless numbers (or characteristic numbers) have an important role in analyzing the behavior of fluids and their flow as well as in other transport phenomena. [1] They include the Reynolds and the Mach numbers, which describe as ratios the relative magnitude of fluid and physical system characteristics, such as density, viscosity, speed of sound, and flow speed.

  9. Water activity - Wikipedia

    en.wikipedia.org/wiki/Water_activity

    The definition of a w is where p is the partial water vapor pressure in equilibrium with the solution, and p* is the (partial) vapor pressure of pure water at the same temperature. An alternate definition can be a w ≡ l w x w {\displaystyle a_{w}\equiv l_{w}x_{w}} where l w is the activity coefficient of water and x w is the mole fraction of ...