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Plot of shear rate as a function of the shear stress. Dilatants in green. A dilatant (/ d aɪ ˈ l eɪ t ə n t /, / d ɪ-/) (also termed shear thickening [1]) material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the initialism STF, is an example of a non-Newtonian fluid.
Time-dependent shear thickening behavior. Thixotropy: The longer a fluid is subjected to a shear force, the lower its viscosity. It is a time-dependent shear thinning behavior. Shear thickening: Similar to rheopecty, but independent of the passage of time. Shear thinning: Similar to thixotropy, but independent of the passage of time.
The shear rate at the inner wall of a Newtonian fluid flowing within a pipe [2] is ˙ =, where: ˙ is the shear rate, measured in reciprocal seconds; v is the linear fluid velocity; d is the inside diameter of the pipe.
The viscosity of a non-Newtonian fluid is defined by a power law: [5] = ˙ where η is the viscosity after shear is applied, η 0 is the initial viscosity, γ is the shear rate, and if <, the fluid is shear thinning, >, the fluid is shear thickening,
In a Newtonian fluid, the relation between the shear stress and the shear rate is linear, passing through the origin, the constant of proportionality being the coefficient of viscosity. In a non-Newtonian fluid, the relation between the shear stress and the shear rate is different. The fluid can even exhibit time-dependent viscosity. Therefore ...
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.
Nonlinear viscoelasticity also elucidates observed phenomena such as normal stresses, shear thinning, and extensional thickening in viscoelastic fluids. [ 3 ] An anelastic material is a special case of a viscoelastic material: an anelastic material will fully recover to its original state on the removal of load.
The consistency is a simple constant of proportionality, while the flow index measures the degree to which the fluid is shear-thinning or shear-thickening. 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 ...