Shear-thickening fluids

Definition

Shear-thickening fluids are non-Newtonian fluids that increase in viscosity when subjected to shear stress, meaning they become thicker and more resistant to flow as the applied force increases. This behavior is contrary to shear-thinning fluids, which become less viscous with increased shear. The properties of shear-thickening fluids have significant implications in fluid dynamics, particularly in the context of the Navier-Stokes equations, where their unique behavior can affect flow patterns and stability.

5 Must Know Facts For Your Next Test

1. Shear-thickening behavior is often observed in colloidal suspensions, where particles interact under stress, causing an increase in resistance to flow.
2. The mechanism behind shear thickening can involve particle interactions and hydrodynamic forces that create temporary structures in the fluid.
3. These fluids can exhibit dramatic changes in viscosity, sometimes becoming nearly solid under high shear rates, which can be useful in applications like body armor.
4. Examples of shear-thickening fluids include cornstarch mixed with water (oobleck) and certain polymer solutions.
5. In the context of fluid dynamics and the Navier-Stokes equations, modeling shear-thickening behavior requires additional terms or modifications to account for changes in viscosity with shear.

Review Questions

• How do shear-thickening fluids differ from shear-thinning fluids in terms of viscosity response to applied stress?
  • Shear-thickening fluids increase in viscosity when subjected to higher levels of shear stress, becoming thicker and more resistant to flow. In contrast, shear-thinning fluids decrease in viscosity under the same conditions, allowing them to flow more easily as stress increases. This fundamental difference is crucial for understanding their behavior in various applications and for accurately modeling them using fluid dynamics equations.
• Discuss the implications of shear-thickening behavior on the modeling of fluid dynamics using the Navier-Stokes equations.
  • The presence of shear-thickening behavior necessitates adjustments in how the Navier-Stokes equations are applied. Traditional formulations assume constant viscosity; however, shear-thickening fluids exhibit a dynamic viscosity that changes with shear rate. This means that additional terms may need to be incorporated into the equations to accurately describe the flow dynamics and predict stability under varying conditions.
• Evaluate the practical applications of shear-thickening fluids and how they leverage their unique properties in engineering or safety solutions.
  • Shear-thickening fluids have practical applications that exploit their unique properties, particularly in areas like protective gear and body armor. When impacted with a high force, these materials become rigid and absorb energy, providing enhanced protection. This behavior is advantageous in engineering designs where materials must respond dynamically to external stresses. Furthermore, advancements in technology allow for better integration of these fluids into various products, illustrating their versatility and importance in safety applications.

Related terms

Viscosity: A measure of a fluid's resistance to deformation or flow, which is influenced by factors such as temperature and shear rate.

Non-Newtonian fluids: Fluids whose viscosity changes with the rate of shear strain, unlike Newtonian fluids, which have a constant viscosity regardless of the shear rate.

Bingham plastic: A type of non-Newtonian fluid that behaves as a solid until a certain yield stress is applied, after which it flows like a viscous fluid.