Week 2: Rheology I: Flow Behaviour

In-class walkthrough of Newtonian, power-law and Herschel-Bulkley flow — reading a flow curve to tell "thick" apart from "won't move until pushed."

1 March 2027

Outline#

• Recap: Module 1 gave us G′, G″ and tan δ for a material sitting still. This lecture asks the companion question — what happens once it flows?
• Live comparison of two flow curves: a Newtonian fluid (honey) against a yield-stress fluid (doubanjiang), read directly off shear stress vs. shear rate rather than described in words first.
• Building the Herschel-Bulkley equation term by term on the board, ending on the yield-stress term and why it is the one number that separates “thick” from “won’t move until pushed.”
• Naming shear-thinning and shear-thickening as the two ways a fluid’s apparent viscosity can depend on how hard you push it, with a kitchen example of each.
• Preview of the Module 2 activity: fitting a real flow curve in the Virtual Rheometer and deciding which of the three models actually fits, not just which one runs.
• Forward pointer: Module 10 revisits this exact fitting problem with the tools to judge a fit rigorously, once residuals are on the table.