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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.
The use of the word "law" in referring to the Glen-Nye model of ice rheology may obscure the complexity of factors which determine the range of viscous ice flow parameter values even within a single glacier, as well as the significant assumptions and simplifications made by the model itself. [13] [14] [7]
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 ...
The Herschel–Bulkley fluid is a generalized model of a non-Newtonian fluid, in which the strain experienced by the fluid is related to the stress in a complicated, non-linear way. Three parameters characterize this relationship: the consistency k , the flow index n , and the yield shear stress τ 0 {\displaystyle \tau _{0}} .
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.
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.
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.