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kinematic viscosity

is given by:

(21.4)

Here is an example of same typical materials’ dynamic viscosity:

It is often considered to be constant, but in general it is function^21.1 of at least six parameters.

(21.5)

– denotes the physical-chemical nature of a substance being the primary influence on viscosity.
– is linked to the temperature of substance. Experience shows that viscosity is heavily influenced by changes of temperature. In general holds for liquids: the viscosity decreases when temperature increases, and for gases: the viscosity increases when temperature increases.
– shear rate is important factor influencing viscosity of many fluids, the viscosity can either decrease or increase with shear rate, this dependency will be discussed in chapter 3.
– pressure is not experienced as often as previous parameters. Pressure compresses fluids and increases intermolecular resistance. Viscosity can increase.
– time denotes the phenomenon that the viscosity of some substances, usually dispersions, depends on previous shear history.
– parameter electrical field is related to a family of suspensions characterized by the phenomenon that their flow behavior is strongly influenced by the magnitude of electrical field acting upon them. These suspensions are called “electro-viscous fluids”.

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