vis·cos·i·ty ˌviˈskäsitē/Submit noun noun: viscosity the state of being thick, sticky, and semifluid in consistency, due to internal friction. synonyms: thickness, gooeyness, viscidity; More a quantity expressing the magnitude of internal friction, as measured by the force per unit area resisting a flow in which parallel layers unit distance apart have unit speed relative to one another. plural noun: viscosities The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal notion of thickness. For example, honey has a much higher viscosity than water.[1] Viscosity is due to the friction between neighboring particles in a fluid that are moving at different velocities. When the fluid is forced through a tube, the fluid generally moves faster near the axis and very slowly near the walls; therefore, some stress (such as a pressure difference between the two ends of the tube) is needed to overcome the friction between layers and keep the fluid moving. For the same velocity pattern, the stress required is proportional to the fluids viscosity. A liquids viscosity depends on the size and shape of its particles and the attractions between the particles.[citation needed] A fluid that has no resistance to shear stress is known as an ideal fluid or inviscid fluid. Zero viscosity is observed only at very low temperatures, in superfluids. Otherwise all fluids have positive viscosity. If the viscosity is very high, for instance in pitch, the fluid will appear to be a solid in the short term. A liquid whose viscosity is less than that of water is sometimes known as a mobile liquid, while a substance with a viscosity substantially greater than water is called a viscous liquid.
Posted on: Mon, 07 Jul 2014 10:52:09 +0000
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