(316q) Comparison of Experimental Results and Model Predictions for Complex Geometry Flows of a Concentrated Suspension

Suspension flows are encountered in many industrial applications, including materials processing (especially ceramic injection molding), solid rocket propellant processing, and inkjet printing. However, uncertainties regarding constitutive relations remain in the current continuum models used to predict the flow behavior in these systems, especially where local flow kinematics are not governed by pure shear. This work focuses on low Reynolds number flow in the abrupt annular expansion/contraction geometry, which contains regions of both shear and extensional flow and therefore provides a challenging test geometry for the models. Nuclear magnetic resonance imaging (NMRI) is used to measure the concentration and velocity profiles of noncolloidal concentrated suspensions undergoing pressure-driven flow through an abrupt, axisymmetric 1:4 expansion or contraction. These results are compared with the predictions of existing continuum models. In particular, the particle concentration profiles, axial development lengths, and pressure drop in the system are compared to model predictions for suspensions of 50% particle volume fraction.