Physics:Poise (unit)
| poise | |
|---|---|
| Unit system | Centimetre–gram–second system of units |
| Unit of | Dynamic viscosity |
| Symbol | P |
| Named after | Jean Léonard Marie Poiseuille |
| Derivation | 1 P = 1 dyn⋅s/cm2 |
| Conversions | |
| 1 P in ... | ... is equal to ... |
| CGS base units | 1 cm−1⋅g⋅s−1 |
| SI units | 0.1 Pa⋅s |
The poise (symbol P; /pɔɪz, pwɑːz/) is the unit of dynamic viscosity (absolute viscosity) in the centimetre–gram–second system of units (CGS).[1] It is named after Jean Léonard Marie Poiseuille (see Hagen–Poiseuille equation). The centipoise (1 cP = 0.01 P) is more commonly used than the poise itself.
Dynamic viscosity has dimensions of [math]\displaystyle{ \mathrm{force \times time/area} }[/math], that is, [math]\displaystyle{ [\mathsf{M}^1 \mathsf{L}^{-1} \mathsf{T}^{-1}] }[/math].
[math]\displaystyle{ 1~\text{P} = 0.1~\text{m}^{-1} {\cdot} \text{kg} {\cdot} \text{s}^{-1} = 1~\text{cm}^{-1} {\cdot} \text{g} {\cdot} \text{s}^{-1} = 1~\text{dyn} {\cdot} \text{s} {\cdot} \text{cm}^{-2}. }[/math]
The analogous unit in the International System of Units is the pascal-second (Pa⋅s):[2]
[math]\displaystyle{ 1~\text{Pa} {\cdot} \text{s} = 1~\text{N} {\cdot} \text{s} {\cdot} \text{m}^{-2} = 1~\text{m}^{-1} {\cdot} \text{kg} {\cdot} \text{s}^{-1} = 10~\text{P}. }[/math]
The poise is often used with the metric prefix centi- because the viscosity of water at 20 °C (standard conditions for temperature and pressure) is almost exactly 1 centipoise.[3] A centipoise is one hundredth of a poise, or one millipascal-second (mPa⋅s) in SI units (1 cP = 10−3 Pa⋅s = 1 mPa⋅s).[4]
The CGS symbol for the centipoise is cP. The abbreviations cps, cp, and cPs are sometimes seen.
Liquid water has a viscosity of 0.00890 P at 25 °C at a pressure of 1 atmosphere (0.00890 P = 0.890 cP = 0.890 mPa⋅s).[5]
See also
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.
- ↑ Lide, David R. (1994). CRC Handbook of Thermophysical and Thermochemical Data. (1st ed.). CRC Press.
- ↑ "Viscosity of Liquids", in CRC Handbook of Chemistry and Physics, 91st Edition, W.M. Haynes, ed., CRC Press/Taylor and Francis, Boca Raton, Florida, 2010-2011.
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