Herschel-Bulkley model

The Herschel-Bulkley model describes how certain complex fluids, like toothpaste or ketchup, flow. It shows that these materials need a minimum force, called yield stress, to start moving. Once they flow, their flow rate depends on the applied force following a specific mathematical relationship. This model accounts for both the initial resistance to movement and how the fluid's viscosity changes with the force applied. It's useful for understanding and predicting the behavior of non-Newtonian fluids that don’t flow like regular liquids, especially when they resist flow initially before becoming more fluid-like.