Dynamics of a mechanical interface in shear-banded flow

Shear banding of wormlike micelle solution has been studied in the context of constitutive instability of the Johnson-Segalman (JS) model plus Newtoni an stress. We have incorporated a higher-order gradient term of the deforma tion-rate tensor into the JS model for investigating the dynamics of a mech anical interface in shear-banded flow. Two-dimensional modelling of the new model has been carried out by a general Langrangian-Eulerian scheme. Withi n the unstable region, our results show that the new term plays an importan t role in selecting steady-state shear stress and the selected stress is in dependent of the nominal shear rate. The transit period of reaching the ste ady state can be much longer than the intrinsic relaxation time of the JS f luid. We have verified the experimental evidence on the existence of mechan ical metastable regime, over which hysteresis in flow curve might occur. Th e model captures many features of experimental results on shear banded flow .