(240g) Numerical Simulations of Free-Surface Flows of a Carbopol Solution

Many materials present in industrial processes, such as polymer solutions, foams, and emulsions exhibit elastic and/or yielding behavior. In this study, we perform numerical simulations of a model yield stress fluid, Carbopol, filling a rectangular mold with and without an obstruction present. For one approach, we use a Saramito model to describe the rheology of the fluid (Saramito, "A new constitutive equation for elastoviscoplastic fluid flows." Journal of Non-Newtonian Fluid Mechanics 145.1 (2007): 1-14). This model describes the material as a Maxwell fluid above yield and an elastic solid below yield with a yield criterion based on the von Mises stress. Thus, the fluid exhibits and constant viscosity but also has elasticity. For the second approach, we consider a generalized Newtonian approach using a Bingham-Carreau-Yasuda (BCY) model. This fluid has shear thinning, a yield stress, but no elasticity for describing the fluid rheology. Conservation equations for momentum and mass with either the BCY or Saramito constitutive equations are solved using the finite element method coupled to a free-surface moving mesh algorithm. We compare numerical results from both models to validation experiments using flow visualization in a quasi-two-dimensional flow where fluid fills a thin gap between transparent plates. Furthermore, we assess the impact of placing an obstruction on flow behavior and compare computations from both constitutive equations considered.