4. Conclusion

Viscosity is a physical quantity that characterizes a fluid's resistance to flow. This concept is relatively easy to grasp when working with simple liquids such as water. But when it comes to fluids with a complex microstructure, a number of questions arise, requiring the clarification of various notions concerning both the material and the type of flow envisaged.

The material can be rheofluidifying or rheo-thickening, thixotropic or antithixotropic, viscoelastic or stress threshold. These different types of behavior result from modifications to the microstructure under flow conditions. This article reviews the main findings concerning two major families of non-Newtonian fluids: suspensions of solid particles and solutions of macromolecules.

Two main types of flow were considered: simple shear flow and uniaxial elongational flow. Thus, the...