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| '''Viscosity''' is the "thickness" or "thinness" of a ]; it |
'''Viscosity''' is the "thickness" or "thinness" of a ]; it is a property of fluids describing their internal resistance to flow and may be thought of as a measure of fluid ]. ] is the field of ] that deals with viscosity; viscosity is measured with a ]. | ||
| If the viscosity of a fluid is constant (neglecting ] and ] effects) it is said to be a Newtonian fluid. ]s exhibit a variation of viscosity depending on ] within the flow field, the history that a fluid 'particle' experiences on its flow path, etc. If the viscosity of a fluid depends solely on the gradients within the flow field it is called generalized Newtonian or purely Newtonian. | If the viscosity of a fluid is constant (neglecting ] and ] effects) it is said to be a Newtonian fluid. ]s exhibit a variation of viscosity depending on ] within the flow field, the history that a fluid 'particle' experiences on its flow path, etc. If the viscosity of a fluid depends solely on the gradients within the flow field it is called generalized Newtonian or purely Newtonian. | ||
| Generally, viscosity is measured at '''25 |
Generally, viscosity is measured at '''25°C''' (]). | ||
| The viscosity of fluids is either given as absolute or '''dynamic viscosity''' η (]·] = ]]/]<sup>2</sup> = ]/]]) or as '''kinematic viscosity''' ν (]<sup>2</sup>/]). Both terms are related via the ] ρ to each other: <math>\eta = \nu \cdot \rho</math>. The old smaller ] ] for dynamic viscosity is '']'' after ] (]-]): 1 poise = 100 centipoise = 1 ]/]] = 0.1 Pa·s. The old unit for kinematic viscosity is '']'' (in ] called ''stoke'') after ] (]-]): 1 stokes = 1 ]<sup>2</sup>/] = 0.0001 ]<sup>2</sup>/]. | The viscosity of fluids is either given as absolute or '''dynamic viscosity''' ''η'' (1 ]·] = 1 ]·]/]<sup>2</sup> = 1 ]/]·]) or as '''kinematic viscosity''' ''ν'' (]<sup>2</sup>/]). Both terms are related via the ] ''ρ'' to each other: <math>\eta = \nu \cdot \rho</math>. The old smaller ] ] for dynamic viscosity is '']'' after ] (]-]): 1 poise = 100 centipoise = 1 ]/]·] = 0.1 Pa·s. The old unit for kinematic viscosity is '']'' (in ] called ''stoke'') after ] (]-]): 1 stokes = 1 ]<sup>2</sup>/] = 0.0001 ]<sup>2</sup>/]. | ||
| ] uses Cps. | ] uses Cps. | ||
Revision as of 18:24, 4 November 2003
Viscosity is the "thickness" or "thinness" of a fluid; it is a property of fluids describing their internal resistance to flow and may be thought of as a measure of fluid friction. Rheology is the field of science that deals with viscosity; viscosity is measured with a viscometer.
If the viscosity of a fluid is constant (neglecting temperature and pressure effects) it is said to be a Newtonian fluid. Non-Newtonian fluids exhibit a variation of viscosity depending on gradients within the flow field, the history that a fluid 'particle' experiences on its flow path, etc. If the viscosity of a fluid depends solely on the gradients within the flow field it is called generalized Newtonian or purely Newtonian.
Generally, viscosity is measured at 25°C (standard state).
The viscosity of fluids is either given as absolute or dynamic viscosity η (1 Pa·s = 1 N·s/m = 1 kg/m·s) or as kinematic viscosity ν (m/s). Both terms are related via the fluid density ρ to each other: . The old smaller cgs physical unit for dynamic viscosity is poise after Jean Louis Marie Poiseuille (1797-1869): 1 poise = 100 centipoise = 1 g/cm·s = 0.1 Pa·s. The old unit for kinematic viscosity is stokes (in U.S. called stoke) after George Gabriel Stokes (1819-1903): 1 stokes = 1 cm/s = 0.0001 m/s.
. The old smaller ASTM uses Cps.
Methanol is "thin", having a low viscosity, while vegetable oil is "thick" having a high viscosity.
Some dynamic viscosities of Newtonian fluids are listed below:
- acetone 0.326 × 10 Pa·s
- benzene 0.64 × 10 Pa·s
- castor oil 985 × 10 Pa·s
- ethyl alcohol 0.248 × 10 Pa·s
- glycerol 1485 × 10 Pa·s
- methanol 0.59 × 10 Pa·s
- mercury 17.0 × 10 Pa·s
- nitrobenzol 2.0 × 10 Pa·s
- sulfuric acid 30 × 10 Pa·s
- olive oil 81 × 10 Pa·s
- pitch 10 Pa·s
- water 1.025 × 10 Pa·s
Contrary to many assertions, glass is an amorphous solid, not a liquid, and it does not flow, but still we can talk about its viscosity. See the article on glass for more details on this.
Many fluids such as honey have a wide range of viscosity.
Viscosity is also an out-of-print image and animation editing utility published by Sonic Foundry. It can work with PNG, GIF, JPG/JPEG, BMP, AVI and its native VSC format.