Question

With proper Rheological diagrams and suitable examples for each, discuss all the different types of non-Newtonian fluids whose viscosity changes with the applied shear rate only.

Answer 1

Non-Newtonian Fluids

In reality, most fluids are non-Newtonian, which means that their viscosity is dependent on the shear rate (Shear Thinning or Thickening) or the deformation history (Thixotropic fluids). In contrast to Newtonian fluids, non-Newtonian fluids display either a non-linear relation between shear stress and shear rate, have yield stress, or viscosity that is dependent on time or deformation history (or a combination of all the above!).

Type of behavior	Description	Example

Shear-thinning	Viscosity decreases with increased stress	Tomato sauce, Nail polish, whipped cream, molasses, syrups, paper pulp in water, latex paint, ice, blood, some silicone oils, some silicone coatings, sand in water
Dilatant or shear thickening	Viscosity increases with increased stress	Oobleck