Interplay of flow-induced phase separations and rheological behavior of complex fluids in shearbanding flow
Department of Mechanical Engineering, King's College London
Strand, London WC2R 2LS, UK
2 H. H. Wills Physics Laboratory, University of Bristol Royal Fort, Tyndall Avenue, Bristol BS8 1TL, UK
Accepted: 16 September 2002
The generic behavior of both flow-induced phase separations and rheological responses of complex fluids has been studied. We solve a two-fluid model numerically in a strong-flow regime without using the diffusive equation linearization and adiabatic approximation. Our results show that the formation of the mechanical shear bands and the fluid composition bands can be closely interrelated. We have identified correlations between the microstructure evolution and rheology, and also different mechanisms to reach the steady state. The rheological signature of demixing fluids under shear is that the dependence of the steady-state shear stress on shear rate changes from non-linear to linear. The model selects a steady-state stress in a natural physical way for non-monotonic constitutive equations under strong flow.
PACS: 47.20.Hw – Morphological instability; phase changes / 47.50.+d – Non-Newtonian fluid flows / 83.60.Df – Nonlinear viscoelasticity
© EDP Sciences, 2002