Seminar

Many common fluids, such as shampoo and ketchup, show yield stress behavior which is more complex than that of simple models like the Bingham fluid. Phenomena which are observed include yield stress hysteresis, shear banding, delayed yielding and thixotropy. It will be shown how such phenomena can be obtained from a viscoelastic model, in the limit where the relaxation time is large. The presence of a small parameter naturally makes the model amenable to methods of singular perturbation theory. The dynamics of yielding and unyielding, oscillatory flow, and the temporal development of shear bands will be discussed.