Dynamic viscosity is an empirical function of temperature, and kinematic viscosity is calculated by dividing dynamic viscosity by the density. the vertical pressure variation, which relates pressure, density and geopotential altitude (using a standard pressure of 101,325 pascals (14.696 psi) at mean sea level as a boundary condition):ĭ P d h = − ρ g Īt each geopotential altitude, where g is the standard acceleration of gravity, and R specific is the specific gas constant for dry air.Īir density must be calculated in order to solve for the pressure, and is used in calculating dynamic pressure for moving vehicles.The other two values (pressure P and density ρ) are computed by simultaneously solving the equations resulting from: The USSA mathematical model divides the atmosphere into layers with an assumed linear distribution of absolute temperature T against geopotential altitude h. Each tiny cube (such as the one representing krypton) has one millionth of the volume of the entire block. Water vapor is not included, as this is highly variable. Visualization of composition by volume of Earth's atmosphere. It is largely consistent in methodology with the International Standard Atmosphere, differing mainly in the assumed temperature distribution at higher altitudes. Committee on Extension to the Standard Atmosphere, and was updated in 1962, 1966, and 1976.
The model, based on an existing international standard, was first published in 1958 by the U.S. Standard Atmosphere 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. Comparison of the 1962 US Standard Atmosphere graph of geometric altitude against air density, pressure, the speed of sound and temperature with approximate altitudes of various objects. Not to be confused with International Standard Atmosphere.
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