Transition and Turbulent Flow of GNF in Pipes-1 — Lesson 1

This lesson covers the transition and turbulent flow of generalized Newtonian fluids in pipes. It begins with a recap of previous lessons, discussing the derivation of velocity profiles, volumetric flow rates, and friction factors for different types of fluids, including power law fluids, Ellis model fluids, Bingham plastics, and Herschel-Bulkley fluids. The lesson then delves into the criteria for transition from laminar to turbulent flow for non-Newtonian fluids. It discusses the critical Reynolds number and how it varies depending on the type and degree of non-Newtonian behavior. The lesson also covers the friction factor for viscoplastic fluids under transition and turbulent conditions. It concludes with a few example problems to illustrate the concepts discussed.

Video Highlights

01:47 - Explanation of the concept of shear stress and its derivation for different types of non-Newtonian fluids.
14:14 - Discussion on the models proposed by Hanks for Bingham plastic fluids and Slatter for Herschel-Bulkley fluids.
21:25 - Explanation of the process of finding the maximum permissible velocity for laminar flow conditions using the models of Hanks and Slatter.
38:06 - Discussion on the concept of friction factor for generalized Newtonian fluids flowing under turbulent conditions.
41:58 - Explanation of the semi-empirical equation proposed by Darby for viscoplastic fluids.

Key Takeaways

• The transition from laminar to turbulent flow in non-Newtonian fluids depends on the type and degree of non-Newtonian behavior.
• The critical Reynolds number for non-Newtonian fluids is primarily based on experimental information and can vary significantly.
• The friction factor for viscoplastic fluids under transition and turbulent conditions can be determined using semi-empirical equations.
• Understanding these concepts is crucial for designing and operating systems involving the flow of non-Newtonian fluids.