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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, a constant coefficient of viscosity cannot be defined. Although the concept of viscosity is commonly used in fluid mechanics to characterize the shear properties of a fluid, it can be ...
However, non-Newtonian fluids are relatively common and include oobleck (which becomes stiffer when vigorously sheared) and non-drip paint (which becomes thinner when sheared). Other examples include many polymer solutions (which exhibit the Weissenberg effect ), molten polymers, many solid suspensions, blood, and most highly viscous fluids.
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.
When a material exhibits a linear response it is categorized as a Newtonian material. In this case the stress is linearly proportional to the strain rate. If the material exhibits a non-linear response to the strain rate, it is categorized as non-Newtonian fluid. There is also an interesting case where the viscosity decreases as the shear ...
Both these fluids show the behavior of a non-Newtonian fluid, behaving like a liquid under low or normal pressure and solid under higher pressure or applied fields. The shear thickening fluid is normally made with polyethylene glycol and the solid part is made of nano-particles of silica.
Let’s talk science: A non-Newtonian fluid is defined as a liquid that does not follow Newton’s law of viscosity. Ultimately, a non-Newtonian fluid will change under force to be either more ...
If a fluid does not obey this relation, it is termed a non-Newtonian fluid, of which there are several types. Non-Newtonian fluids can be either plastic, Bingham plastic, pseudoplastic, dilatant, thixotropic, rheopectic, viscoelastic. In some applications, another rough broad division among fluids is made: ideal and non-ideal fluids.
Classification of fluids with shear stress as a function of shear rate: Pseudoplastic, Bingham plastic and Bingham pseudoplastic all show reduction in apparent viscosity with increasing shear rate. In rheology , shear thinning is the non-Newtonian behavior of fluids whose viscosity decreases under shear strain .