| A sphere falling through a wormlike micellar solution (A surfactant solution) does not approach a steady state - instead it oscillates as it falls. Bubbles rising through this solution also displays this oscillatory behaviour. The micellar fluid is often modelled with consitutive equations which display non-monotonic stress-strain relationship. In this talk, we will argue that these oscillations can be explained as a "instability" in the constitutive equations which display non-monotonic stress-strain relationship. |