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Consequently, if a liquid has dynamic viscosity of n centiPoise, and its density is not too different from that of water, then its kinematic viscosity is around n centiStokes. For gas, the dynamic viscosity is usually in the range of 10 to 20 microPascal-seconds, or 0.01 to 0.02 centiPoise. The density is usually on the order of 0.5 to 5 kg/m^3.
Viscosity is a measure of a fluid's rate-dependent resistance to a change in shape or to movement of its neighboring portions relative to one another. [1] For liquids, it corresponds to the informal concept of thickness; for example, syrup has a higher viscosity than water. [2]
Viscous flow in amorphous materials is characterised by deviations from the Arrhenius-type behaviour: the activation energy of viscosity Q changes from a high value Q H at low temperatures (in the glassy state) to a low value Q L at high temperatures (in the liquid state).
Boger fluids are named after David V. Boger, who in the late 1970s was the primary researcher pushing for the study of constant viscosity elastic liquids. [2] He released his first paper on Boger fluids in 1977, titled "A Highly Elastic Constant-Viscosity Fluid", where he described the ideal fluid for experimentation as a fluid that is "highly viscous and highly elastic at room temperature and ...
The University of Queensland pitch drop experiment, demonstrating the viscosity of bitumen. A pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. "Pitch" is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen, also known as asphalt. At room ...
the fluid is assumed to be isotropic, as with gases and simple liquids, and consequently is an isotropic tensor; furthermore, since the deviatoric stress tensor is symmetric, by Helmholtz decomposition it can be expressed in terms of two scalar Lamé parameters, the second viscosity and the dynamic viscosity, as it is usual in linear elasticity:
The dilute gas viscosity contribution to the total viscosity of a fluid will only be important when predicting the viscosity of vapors at low pressures or the viscosity of dense fluids at high temperatures. The viscosity model for dilute gas, that is shown above, is widely used throughout the industry and applied science communities.
A Newtonian fluid is a power-law fluid with a behaviour index of 1, where the shear stress is directly proportional to the shear rate: = These fluids have a constant viscosity, μ, across all shear rates and include many of the most common fluids, such as water, most aqueous solutions, oils, corn syrup, glycerine, air and other gases.