Non-newtonian fluid behavior

Definition

Non-newtonian fluid behavior refers to the characteristics of fluids whose viscosity changes under different conditions of stress or shear rate, unlike Newtonian fluids that have a constant viscosity. This unique property means that non-newtonian fluids can exhibit complex behaviors, such as becoming thinner or thicker when stirred or subjected to force. Understanding non-newtonian fluids is crucial in fluid dynamics and is modeled by the Navier-Stokes equations, which describe how these fluids flow under varying forces.

5 Must Know Facts For Your Next Test

1. Non-newtonian fluids can be categorized into types like shear-thinning (pseudoplastic) and shear-thickening (dilatant), depending on how their viscosity changes with stress.
2. Common examples of non-newtonian fluids include ketchup, toothpaste, and cornstarch mixed with water (oobleck), all of which exhibit unique flow properties.
3. The mathematical modeling of non-newtonian fluids often requires modifications to the Navier-Stokes equations to account for their varying viscosity.
4. Understanding non-newtonian fluid behavior is essential in industries such as food processing, cosmetics, and polymer manufacturing, where precise control over flow properties is needed.
5. The study of non-newtonian fluids helps in predicting phenomena like yield stress, elastic recovery, and time-dependent behaviors that are not observed in Newtonian fluids.

Review Questions

• How does non-newtonian fluid behavior differ from Newtonian fluid behavior in terms of viscosity and response to shear stress?
  • Non-newtonian fluid behavior differs significantly from Newtonian fluid behavior in that non-newtonian fluids do not have a constant viscosity. Instead, their viscosity changes based on the applied shear stress. For example, while a Newtonian fluid like water maintains the same viscosity regardless of how hard you stir it, a non-newtonian fluid like ketchup becomes easier to pour when shaken or squeezed but thickens when left undisturbed.
• What role do the Navier-Stokes equations play in understanding the dynamics of non-newtonian fluids?
  • The Navier-Stokes equations are fundamental in fluid dynamics for modeling how fluids behave under various conditions. When it comes to non-newtonian fluids, these equations often need to be adjusted because traditional assumptions about constant viscosity do not apply. By incorporating variable viscosity into these equations, scientists and engineers can more accurately predict how non-newtonian fluids will flow and react under different forces and stresses.
• Evaluate the significance of studying non-newtonian fluids in real-world applications across different industries.
  • Studying non-newtonian fluids is crucial across various industries because these materials are common in everyday products and processes. For example, in the food industry, understanding how sauces and pastes flow affects production and packaging efficiency. In the cosmetic industry, formulating creams and lotions requires knowledge of how they will behave during application. Additionally, advancements in polymer manufacturing depend on controlling flow properties for quality products. Thus, insights into non-newtonian behavior contribute to innovation and efficiency in many sectors.

Related terms

Viscosity: A measure of a fluid's resistance to deformation or flow, indicating how thick or thin a fluid is.

Shear Stress: The force per unit area applied parallel to the surface of a material, which affects how non-newtonian fluids respond to external forces.

Bingham Plastic: A type of non-newtonian fluid that behaves like a solid until a certain yield stress is applied, after which it flows like a liquid.