A novel approach for modeling the mechanical behavior of thixotropic viscoplastic fluids is
presented. Non-monotonic flow curves, stress overshoot during microstructure breakdown
flows at constant shear rate, and viscosity bifurcation are some of the common aspects of
structured fluids that are predicted by the new model. It involves two evolution equations,
one for the stress and the other for the structure parameter. Simple ideas are employed to
describe the microstructure, and, as a result, a model with a clear physical basis is obtained …