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| Viscosity |
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Viscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress. |
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In everyday terms (and for liquids only), viscosity is thickness. Thus, water is thin; having a lower viscosity, while vegetable oil is thick having a higher viscosity. |
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All real fluids (except super fluids) have some resistance to stress, but a fluid which has no resistance to shear stress is known as an ideal fluid or in viscid fluid.
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The study of viscosity is known as rheology. |
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The word viscosity derives from the Latin word viscum for mistletoe.
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Temperature also effects viscosity. Raising the temperature of a fluid tends to make it less viscous. |
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Kinematic viscosity is a measure of the rate at which momentum is transferred through a fluid. It is measured in stokes.
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Dynamic viscosity is a measure of the ratio of the stress on a region of a fluid to the rate of change of strain it undergoes. It is equal to the kinematic viscosity times the density of the fluid. It is measured in pascal-seconds or poises.
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