Non-Newtonian Fluid

Definition

A non-Newtonian fluid is a type of fluid whose viscosity changes when under stress or shear, meaning it doesn't have a constant viscosity like Newtonian fluids. These fluids can behave differently depending on the force applied to them, which makes them unique in various applications including industrial processes and everyday materials. Understanding their behavior is crucial for effective momentum transfer in systems involving these types of fluids.

5 Must Know Facts For Your Next Test

1. Non-Newtonian fluids can be classified into several categories such as shear-thinning (pseudoplastic), shear-thickening (dilatant), and Bingham plastics, each responding differently to applied stress.
2. Common examples of non-Newtonian fluids include ketchup, paint, and certain types of slurries, which exhibit varied flow behavior under different conditions.
3. In industrial applications, non-Newtonian fluids can lead to challenges in pumping and mixing processes due to their variable viscosity.
4. The flow behavior of non-Newtonian fluids can be modeled using various mathematical equations that take into account the relationship between shear stress and shear rate.
5. Understanding how non-Newtonian fluids behave is essential for optimizing equipment design and process efficiency in chemical engineering.

Review Questions

• How does the behavior of non-Newtonian fluids differ from Newtonian fluids under varying shear stress?
  • Non-Newtonian fluids respond differently to shear stress compared to Newtonian fluids, which maintain a constant viscosity regardless of the stress applied. In contrast, non-Newtonian fluids exhibit a change in viscosity; they may become thinner or thicker depending on the amount of shear they experience. For example, a shear-thinning fluid will flow more easily when stirred, while a shear-thickening fluid will resist flow more as stress increases.
• Discuss the significance of thixotropic and dilatant behaviors in non-Newtonian fluids and their implications in real-world applications.
  • Thixotropic fluids decrease in viscosity over time under constant shear, which makes them ideal for applications such as printing inks and certain cosmetics that need to flow easily when applied but hold their shape when at rest. Conversely, dilatant fluids increase in viscosity with shear, making them useful in situations where resistance is beneficial, such as body armor or safety gear. Understanding these behaviors allows engineers to tailor processes and materials to achieve desired performance characteristics.
• Evaluate the impact of non-Newtonian fluid behavior on equipment design and process efficiency within chemical engineering.
  • The variable viscosity of non-Newtonian fluids significantly affects equipment design and process efficiency in chemical engineering. Engineers must consider these unique flow properties when designing pumps, mixers, and reactors to ensure optimal performance and minimize issues like clogging or inconsistent mixing. By accurately modeling how these fluids behave under different conditions, engineers can enhance operational reliability and efficiency, ultimately leading to better product quality and reduced operational costs.

Related terms

Viscosity: The measure of a fluid's resistance to flow, which can change under different conditions for non-Newtonian fluids.

Shear Stress: The force per unit area applied parallel to the surface of a material, affecting the behavior of non-Newtonian fluids.

Thixotropic Fluid: A specific type of non-Newtonian fluid that becomes less viscous over time when subjected to constant shear stress.