Stokes (unit)

Physical unit
Unit name Stokes
Unit symbol ${\ displaystyle \ mathrm {St}}$
Physical quantity (s) kinematic viscosity
Formula symbol ${\ displaystyle \ nu}$
dimension ${\ displaystyle {\ mathsf {L ^ {2} \; T ^ {- 1}}}}$
system CGS system of units
In SI units ${\ displaystyle \ mathrm {1 \, St = 10 ^ {- 4} \; {\ frac {m ^ {2}} {s}}}}$
In CGS units ${\ displaystyle \ mathrm {1 \, St = 1 \; {\ frac {cm ^ {2}} {s}}}}$
Named after George Gabriel Stokes
Derived from Centimeter , second

Stokes ( St ) is the name of the unit cm² / s of the kinematic viscosity in the CGS system of units ; it is named after the Irish mathematician and physicist George Gabriel Stokes . Between 1920 and 1940 the unit was also known as the Lentor .

In business transactions in Germany, the SI unit m² / s has been mandatory since 1978 . In practice, the specification in cSt (centistokes) is common.

Conversion:

${\ displaystyle \ mathrm {1 \, St = 1 \, {\ frac {cm ^ {2}} {s}} = 10 ^ {- 4} \, {\ frac {m ^ {2}} {s} }}}$
${\ displaystyle \ mathrm {1 \, cSt = 1 \, {\ frac {mm ^ {2}} {s}} = 10 ^ {- 6} \, {\ frac {m ^ {2}} {s} }}}$

The Stokes was declared a legal measure in Austria under the name Stok by federal law of July 5, 1950; In 1973 the name was changed to Stokes; since 1988 it is no longer a legal entity.

The unit name Stok was also recommended in the German standard DIN 1342 "Toughness" from August 1936.

Individual evidence

1. ^ François Cardarelli: Scientific Unit Conversion. A Practical Guide to Metrication , Springer Verlag, London 1997, p. 231.
2. Federal Law Gazette No. 174 (1973)
3. Federal Law Gazette No. 742 (1988)