Abstract

Yield-stress fluids and thixotropic fluids are known to exhibit similar flow curves (flow rate vs. pressure drop) in steady shear flows such as Poiseuille flows. Such similarities may lead to i) confusion when identifying constitutive equations, ii) wrong predictions in 3D complex flows. In this presentation, similarities and differences in several complex flows of the simplest yield-stress and thixotropic fluid models that exhibit the same flow curves are studied. To perform the resolution of 2D-3D flows, a finite element method based on an a posteriori error estimation and anisotropic mesh adaptation is proposed. This method, coupled to an explicit treatment of highly nonlinear flow constitutive models, allows capturing extreme localization of high strain rates flow regions such as shear banding. It is shown, in 3D benchmark flows, that for a range of mean (i.e. apparent) strain rates, symmetry breaking and shear banding occur for thixotropic fluid models whereas yield-stress fluid models exhibit smoother flow features.