viscosity

In general, the resistance to flow or alteration of shape by any substance as a result of molecular cohesion; most frequently applied to liquids as the resistance of a fluid to flow because of a shearing force. [L. viscositas, fr. viscosus, viscous]

- absolute v. force per unit area applied tangentially to a fluid, causing unit rate of displacement of parallel planes separated by a unit distance; units in CGS system : poise.

- anomalous v. the viscous behavior of nonhomogenous fluids or suspensions, e.g., blood, in which the apparent v. increases as flow or shear rate decreases toward zero.

- apparent v. the v. calculated from Poiseuille law at any particular flow and tube diameter; it is used for suspensions, such as blood, that exhibit anomalous v. and the Fahraeus-Lindqvist effect.

- dynamic v. (μ) the internal or molecular frictional resistance of a fluid by Newton law of v. as the ratio of the applied force per unit area to the relative velocity of adjacent fluid layers (produced by the force).

- kinematic v. (ν, Υ) a measure used in studies of fluid flow; it is the dynamic v., μ, in poises, divided by the density of the material; unit; stoke.

- newtonian v. the v. characteristics of a newtonian fluid.

- relative v. the ratio of the v. of a solution or dispersion to the v. of the solvent or continuous phase.

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vis·cos·i·ty vis-'käs-ət-ē n, pl -ties

1) the quality of being viscous esp the property of resistance to flow in a fluid or semifluid

2) the ratio of the tangential frictional force per unit area to the velocity gradient perpendicular to the direction of flow of a liquid called also coefficient of viscosity

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vis·cos·i·ty (vis-kosґĭ-te) resistance to flow; a physical property of a substance that depends on the friction of its component molecules as they slide past one another.