Correlations of strain and plasticity in a flowing foam

Abstract

Via simulations of flowing foam, we connect the high- and intermediate-density regimes of complex fluid flows into a consistent microscopic picture of deformation. While at and above the jamming transition, elastic correlations lead to a strong spatial organization of the flow field, below jamming, the slowly diminishing elastic correlation length leads to a slowly ceasing spatial organization, which is nevertheless still present down to densities far below jamming. We show that the long-range–correlated flow field arises from the superposition of quadrupolar strain fields of shear zones with highly correlated positions, strengths and orientation. These interactions are still pertinent below jamming, where they systematically weaken with the slowly diminishing elastic correlation length. These results demonstrate the ubiquity and importance of elastic correlations in the flow of complex fluids even below the jamming transition, and motivate a scale-bridging description of their flow over wide ranges of density from solid to fluid.