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Application
Notes:
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viscosity
is the measurement of a fluid’s internal resistance to
flow. The common metric unit of absolute
viscosity is the poise, which is defined as the force in dynes
required to move a surface one square centimeter in area past a parallel
surface at a speed of one centimeter per second, with the surfaces separated
by a fluid film one centimeter thick. For convenience, the centipoise
(cp) — one one-hundredth of a poise — is the unit customarily used.
Laboratory measurements of viscosity normally use the force of gravity to
produce flow through a capillary tube (viscometer)
at a controlled temperature. This measurement is called
kinematic viscosity. The unit of
kinematic viscosity is the stoke, expressed in square centimeters per
second. The more customary unit is the centistoke (cSt) — one
one-hundredth of a stoke. Kinematic viscosity can be related to absolute
viscosity by the equation:
cSt = cp ÷ fluid density
Additionally to
kinematic viscosity, there are other methods for determining viscosity,
including Saybolt Universal
viscosity, Saybolt Furol
viscosity, Engler viscosity,
and Redwood viscosity. Since
viscosity varies inversely with temperature, its value is meaningless unless
the temperature at which it is determined is reported.
Also see viscosity
(asphalt), V.I. Calculator,
Viscosity Classification, viscosity index,
viscosity-temperature
relationship, viscosity
selection.
.
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- Analytical Almanac
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