Non-Newtonian Fluids and Their Phenomena — Lesson 2

This lesson covers the concept of non-Newtonian fluids, focusing on time-independent non-Newtonian fluids. It explains the characteristics of Newtonian fluids and how non-Newtonian fluids differ from them. The lesson further categorizes non-Newtonian fluids into three types: time-independent, time-dependent, and viscoelastic fluids. It delves into the details of time-independent non-Newtonian fluids, explaining how their apparent viscosity depends on the shear rate and not on the time of shearing. The lesson also discusses different models for shear-thinning fluids, viscoplastic fluids, and shear-thickening fluids. For instance, it explains the power-law model, Carreau viscosity model, and the Herschel-Bulkley fluid model. The lesson concludes with examples of materials that exhibit these fluid behaviors, such as meat extract, Carbopol solution, and beach sand.

Video Highlights

02:11 - Explanation of time-independent non-Newtonian fluids
05:43 - Discussion on shear-thinning fluids
21:30 - Mathematical models for shear-thinning fluids
36:35 - Introduction to viscoplastic fluids
46:41 - Mathematical models for viscoplastic fluids

Key Takeaways

• Non-Newtonian fluids are categorized into time-independent, time-dependent, and viscoelastic fluids.
• Time-independent non-Newtonian fluids have an apparent viscosity that depends on the shear rate and not on the time of shearing.
• Shear-thinning fluids, a type of time-independent non-Newtonian fluids, have an apparent viscosity that decreases with increasing shear rate.
• Viscoplastic fluids, another type of time-independent non-Newtonian fluids, do not deform until the applied stress crosses a certain characteristic yield stress.
• Shear-thickening fluids, the last category of time-independent non-Newtonian fluids, have an apparent viscosity that increases with increasing shear rate.
• Different mathematical models like the power-law model, Carreau viscosity model, and the Herschel-Bulkley fluid model are used to describe these fluid behaviors.