FEM modeling and simulation of thixo-viscoplastic flow problems.

We are concerned, in this work, with Finite Element Method (FEM) for modeling and simulation of thixotropy in viscoplastic materials. We use a quasi-Newtonian approach to integrate the constitutive equation, which results in a new thixo-viscoplastic (TVP) generalized Navier-Stokes (N-S) equations. To solve the corresponding flow fields at once, we developed a FEM TVP solver based on monolithic Newton-multigrid method. The phenomenologi-cal process of competition of breakdown and buildup characteristics of thixotropic material is replicated throughout, localization and shear banding for Couette flow on one hand, and induction of more shear rejuvenation layers nearby walls for contraction flow on the other hand. [ABSTRACT FROM AUTHOR]