Sutherland's law
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- | In 1893 [http://en.wikipedia.org/wiki/William_Sutherland_(physicist) William Sutherland], an Australian physicist, published a relationship between the | + | In 1893 [http://en.wikipedia.org/wiki/William_Sutherland_(physicist) William Sutherland], an Australian physicist, published a relationship between the dynamic viscosity, <math>\mu</math>, and the absolute temperature, <math>T</math>, of an ideal gas. This formula, often called Sutherland's law, is based on kinetic theory of ideal gases and an idealized intermolecular-force potential. Sutherland's law is still commonly used and most often gives fairly accurate results with an error less than a few percent over a wide range of temperatures. Sutherland's law can be expressed as: |
- | :<math>\mu = \ | + | :<math>\mu = \mu_{ref} \left( \frac{T}{T_{ref}} \right)^{3/2}\frac{T_{ref} + S}{T + S}</math> |
- | :<math> | + | :<math>T_{ref}</math> is a reference temperature. |
- | :<math>\ | + | :<math>\mu_{ref}</math> is the viscosity at the <math>T_{ref}</math> reference temperature |
:S is the Sutherland temperature | :S is the Sutherland temperature | ||
Line 13: | Line 13: | ||
Comparing the formulas above the <math>C_1</math> constant can be written as: | Comparing the formulas above the <math>C_1</math> constant can be written as: | ||
- | :<math>C_1 = \frac{\ | + | :<math>C_1 = \frac{\mu_{ref}}{T_{ref}^{3/2}}(T_{ref} + S)</math> |
+ | |||
+ | {| border=2 | ||
+ | |+ Sutherland's law coefficients: | ||
+ | ! Gas !! <math>\mu_0 [\frac{kg}{m s}]</math> !! <math>T_0 [K]</math> !! <math>S [K]</math> !! <math>C_1 [\frac{kg}{m s \sqrt{K}}]</math> | ||
+ | |- | ||
+ | | Air | ||
+ | | <math>1.716 \times 10^{-5}</math> | ||
+ | | <math>273.15</math> | ||
+ | | <math>110.4</math> | ||
+ | | <math>1.458 \times 10^{-6}</math> | ||
+ | |} | ||
== References == | == References == | ||
* {{reference-paper|author=Sutherland, W.|year=1893|title=The viscosity of gases and molecular force|rest=Philosophical Magazine, S. 5, 36, pp. 507-531 (1893)}} | * {{reference-paper|author=Sutherland, W.|year=1893|title=The viscosity of gases and molecular force|rest=Philosophical Magazine, S. 5, 36, pp. 507-531 (1893)}} |
Latest revision as of 04:13, 25 October 2008
In 1893 William Sutherland, an Australian physicist, published a relationship between the dynamic viscosity, , and the absolute temperature, , of an ideal gas. This formula, often called Sutherland's law, is based on kinetic theory of ideal gases and an idealized intermolecular-force potential. Sutherland's law is still commonly used and most often gives fairly accurate results with an error less than a few percent over a wide range of temperatures. Sutherland's law can be expressed as:
- is a reference temperature.
- is the viscosity at the reference temperature
- S is the Sutherland temperature
Some authors instead express Sutherland's law in the following form:
Comparing the formulas above the constant can be written as:
Gas | ||||
---|---|---|---|---|
Air |
References
- Sutherland, W. (1893), "The viscosity of gases and molecular force", Philosophical Magazine, S. 5, 36, pp. 507-531 (1893).