An improved suspension balance model applied to shear-induced phase segregation

Abstract

When suspensions are subject to non-homogeneous shear, particles migrate towards lower-shear rate regions of the flow due to the anisotropy on the particle phase’s normal stress. This phenomenon leads to phase segregation, complicating the interpretation of rheological experimental data for characterising those suspensions. This work presents an improved version of the well-known Suspension Balance Model (SBM), featuring a frame-independent formulation of the particles’ normal stress with an improved momentum interpolation scheme that prevents numerical oscillations. The particle’s stress model also includes a local formulation for the microscopically generated extra stress, ensuring grid convergence. Our model, implemented in OpenFOAM-v7®, successfully simulated various shear-dominated flows. The simulated Couette rheometric data showed that the characterisation of suspensions from such data could not capture their non-Newtonian behaviour. Besides, the obtained rheological model for the suspensions depended on the geometry of the rheometer, being unable to predict the flow of the same suspension in different conditions and geometries.