Non-Newtonian fluid

Non-Newtonian fluid

A non-Newtonian fluid is a fluid whose viscosity is variable based on applied stress or force. Unlike a Newtonian fluid, where the viscosity remains constant regardless of the stresses applied, the viscosity of a non-Newtonian fluid can change when under force, making it either more liquid or more solid. This behavior is a key characteristic that distinguishes non-Newtonian fluids from Newtonian fluids, which have a constant flow regardless of the stress applied.

The study of non-Newtonian fluids falls within the realm of rheology, the science of the flow and deformation of matter. Non-Newtonian fluids can be classified into several types based on their behavior under stress: shear-thinning, shear-thickening, thixotropic, and rheopectic among others.

• Shear-thinning fluids, also known as pseudoplastic fluids, decrease in viscosity when shear stress is applied. An example of a shear-thinning fluid is paint, which becomes less viscous when stirred or brushed.
• Shear-thickening fluids, or dilatant fluids, increase in viscosity when subjected to shear stress. An example is a mixture of cornstarch and water, which can act solid when a sudden force is applied.
• Thixotropic fluids decrease in viscosity over time under constant shear stress, while rheopectic fluids increase in viscosity over time under constant shear stress.

The behavior of non-Newtonian fluids has practical applications in various industries. For example, in the food industry, the consistency of sauces and gravies can be controlled using non-Newtonian principles. In the automotive industry, non-Newtonian fluids are used in shock absorbers and dampers to improve performance under varying conditions.

Understanding the properties of non-Newtonian fluids is also crucial in the field of biomedical engineering, where the behavior of bodily fluids such as blood (which is a non-Newtonian fluid) is essential for the design of medical devices and in the analysis of physiological processes.