Non-Newtonian Fluid

Definition

A non-Newtonian fluid is a fluid that does not follow Newton's law of viscosity, which states that the rate of shear is proportional to the shear stress. These fluids exhibit complex flow behavior that cannot be described by a single constant viscosity value.

5 Must Know Facts For Your Next Test

1. Non-Newtonian fluids exhibit a variable viscosity that changes with the rate of shear, unlike Newtonian fluids which have a constant viscosity.
2. Examples of non-Newtonian fluids include ketchup, paint, blood, toothpaste, and certain types of polymers and suspensions.
3. The viscosity of non-Newtonian fluids can increase or decrease with increasing shear rate, depending on the fluid's specific properties.
4. Non-Newtonian fluids can exhibit behaviors such as shear-thinning, shear-thickening, and yield stress, which are not observed in Newtonian fluids.
5. The complex flow behavior of non-Newtonian fluids can lead to unique and interesting phenomena, such as the formation of vortices and the development of turbulence.

Review Questions

• Explain how the viscosity of a non-Newtonian fluid differs from that of a Newtonian fluid.
  • The viscosity of a non-Newtonian fluid is not constant, as it is in a Newtonian fluid. Instead, the viscosity of a non-Newtonian fluid varies with the rate of shear. This means that as the shear rate changes, the fluid's resistance to flow, or its internal friction, also changes. This complex flow behavior is what distinguishes non-Newtonian fluids from Newtonian fluids, which have a constant viscosity that is independent of the shear rate.
• Describe the relationship between the viscosity of a non-Newtonian fluid and the development of turbulence.
  • The variable viscosity of non-Newtonian fluids can have a significant impact on the development of turbulence. As the shear rate increases, the viscosity of some non-Newtonian fluids may decrease (shear-thinning), which can promote the formation of eddies and vortices, leading to turbulent flow. Conversely, other non-Newtonian fluids may exhibit shear-thickening behavior, where the viscosity increases with shear rate, which can dampen the formation of turbulence. The complex interplay between the fluid's viscosity and the shear rate can result in unique and unpredictable turbulent flow patterns in non-Newtonian fluids.
• Analyze the implications of the non-Newtonian behavior of fluids in various industrial and biological applications.
  • The non-Newtonian behavior of fluids has important implications in a wide range of applications. In industrial settings, the ability to control the viscosity of non-Newtonian fluids, such as paints, coatings, and polymers, allows for better processing, mixing, and application. In the human body, the non-Newtonian properties of blood and other biological fluids play a crucial role in their transport and function. For example, the shear-thinning behavior of blood allows it to flow more easily through narrow blood vessels, while the yield stress of synovial fluid in joints helps to provide lubrication and support. Understanding and leveraging the non-Newtonian characteristics of fluids is essential for designing effective and efficient systems in various industries and biological contexts.

Related terms

Viscosity: The measure of a fluid's resistance to flow, or its internal friction. Viscosity determines a fluid's thickness and how easily it flows.

Shear Stress: The stress component perpendicular to the face of an infinitesimal element within a fluid, caused by the fluid's flow.

Turbulence: The irregular, chaotic, and unpredictable flow of a fluid, characterized by eddies, vortices, and other complex flow patterns.