RHEOLOGICAL CHARACTERIZATION OF YIELD-STRESS MATERIALS: FLOW PATTERN AND APPARENT WALL SLIP

An experimental and numerical investigation of the rotational rheometry of yield-stress materials is performed, using water-based Carbopol dispersions. The flow and fluid characterization in different rheometer geometries, namely the smooth Couette, the grooved Couette, and the vane-in-cup are analysed. The bi-dimensional flow governing equations are solved numerically, using the finite volume method and Fluent software (Ansys Inc.). The viscoplastic behavior of Carbopol dispersions is modeled using the Generalized Newtonian constitutive equation with the regularized viscoplastic viscosity function proposed by de Souza Mendes and Dutra [1], herein called SMD function. The flow pattern and the presence of apparent wall slip in rheometric measurements of yield-stress materials are investigated and discussed.