Poise (unit)

The poise (symbol P; English: /ˈpɔɪzˌˈpwɑːz/) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units.^[1] It is named after Jean Léonard Marie Poiseuille.

1~{\text{P}}=0.1~{\text{kg}}\cdot {\text{m}}^{-1}\cdot {\text{s}}^{-1}=1~{\text{g}}\cdot {\text{cm}}^{-1}\cdot {\text{s}}^{-1}=1~{\text{dyne}}\cdot {\text{s}}\cdot {\text{cm}}^{-2}.

The analogous unit in the International System of Units is the pascal-second (Pa·s):^[2]

1~{\text{Pa}}\cdot {\text{s}}=1~{\text{N}}\cdot {\text{s}}\cdot {\text{m}}^{-2}=1~{\text{kg}}\cdot {\text{m}}^{-1}\cdot {\text{s}}^{-1}=10~{\text{P}}.

The poise is often used with the metric prefix centi- because the viscosity of water at 20 °C is almost exactly 1 centipoise.^[3] A centipoise is one hundredth of a poise, equal to one millipascal-second (mPa·s) in SI units (1 cP = 10⁻³ Pa·s = 1 mPa·s).

The CGS symbol for the centipoise is cP. The abbreviations cps, cp, and cPs are sometimes seen.

Water has a viscosity of 0.00890 P at 25 °C and a pressure of 1 atmosphere (0.00890 P = 0.890 cP = 0.890 mPa-s).^[4]

References

^ Gooch, Jan W. (2010). Encyclopedia dictionary of polymers (2nd ed.). Berlin: Springer. ISBN 978-1-4419-6246-1.
^ Reid, Robert C. (1987). The Properties of Gases and Liquids (4th ed.). McGraw-Hill.
^ Parker, Sybil P. (1988). Fluid Mechanics Source Book (1st ed.). McGraw-Hill.
^ "Viscosity of Liquids", in CRC Handbook of Chemistry and Physics, 91st Edition, W.M. Haynes, ed., CRC Press/Taylor and Francis, Boca Raton, FL, 2010-2011.

[1] Gooch, Jan W. (2010). Encyclopedia dictionary of polymers (2nd ed.). Berlin: Springer. ISBN 978-1-4419-6246-1.

[2] Reid, Robert C. (1987). The Properties of Gases and Liquids (4th ed.). McGraw-Hill.

[3] Parker, Sybil P. (1988). Fluid Mechanics Source Book (1st ed.). McGraw-Hill.

[4] "Viscosity of Liquids", in CRC Handbook of Chemistry and Physics, 91st Edition, W.M. Haynes, ed., CRC Press/Taylor and Francis, Boca Raton, FL, 2010-2011.

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See also

References