(522a) Non-Viscometric Flow of Yield Stress Fluids: Flow Visualization, Velocimetry and Finite Element Modeling

Many multiphase materials of commercial interest including foams, emulsions and concentrated suspensions exhibit a yielding transition where material response transitions from primarily solid to liquid. In non-viscometric flows, there can also be coexisting regions of solid-like and liquid-like material. We will present new flow visualization experiments and finite element modeling of a Carbopol gel injected between two vertical clear plates. Apparent slip at the plates results in a quasi-2D plug flow. Particle tracking is used to measure local transient velocities, shear rates and local arrest as the fluid moves away from the injection point. Finite element calculations utilize a Saramito constitutive equation that 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. Conservation equations for momentum and mass and the Saramito constitutive equations for stress are solved using the finite element method coupled to a free-surface moving mesh algorithm. Simulation results are validated against literature results for a ball falling in a tube and then compared to plate flow experiments. Simulation predictions match qualitatively for the free surface shape of the yield stress fluid and allow analysis of yield surfaces within the flow.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2021-4388 A