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The predictions of the first three models (hard-sphere, power-law, and Sutherland) can be simply expressed in terms of elementary functions. The Lennard–Jones model predicts a more complicated T {\displaystyle T} -dependence, but is more accurate than the other three models and is widely used in engineering practice.
For example, if n were less than one, the power law predicts that the effective viscosity would decrease with increasing shear rate indefinitely, requiring a fluid with infinite viscosity at rest and zero viscosity as the shear rate approaches infinity, but a real fluid has both a minimum and a maximum effective viscosity that depend on the ...
The simplest model of the dense fluid viscosity is a (truncated) power series of reduced mole density or pressure. Jossi et al. (1962) [14] presented such a model based on reduced mole density, but its most widespread form is the version proposed by Lohrenz et al. (1964) [15] which is displayed below.
Where: , , and are material coefficients: is the viscosity at zero shear rate (Pa.s), is the viscosity at infinite shear rate (Pa.s), is the characteristic time (s) and power index. The dynamics of fluid motions is an important area of physics, with many important and commercially significant applications.
In rheology, shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain. It is sometimes considered synonymous for pseudo- plastic behaviour, [ 1 ] [ 2 ] and is usually defined as excluding time-dependent effects, such as thixotropy .
The power law model is used to display the behavior of Newtonian and non-Newtonian fluids and measures shear stress as a function of strain rate. The relationship between shear stress, strain rate and the velocity gradient for the power law model are: τ x y = − m | γ ˙ | n − 1 d v x d y , {\displaystyle \tau _{xy}=-m\left|{\dot {\gamma ...
Ordinary paint is one example of a shear-thinning fluid, while oobleck provides one realization of a shear-thickening fluid. Finally, the yield stress quantifies the amount of stress that the fluid may experience before it yields and begins to flow. This non-Newtonian fluid model was introduced by Winslow Herschel and Ronald Bulkley in 1926. [1 ...
In fluid dynamics, a Cross fluid is a type of generalized Newtonian fluid whose viscosity depends upon shear rate according to the Cross Power Law equation: (˙) = + + (˙)where (˙) is viscosity as a function of shear rate, is the infinite-shear-rate viscosity, is the zero-shear-rate viscosity, is the time constant, and is the shear-thinning index.