Abstract
In this work we study the effect of an additional mechanical noise on the rheological features of yield stress materials that exhibit non-homogeneous steady flows. Using a mesoscale elasto-plastic model accounting for a viscosity bifurcation in the flow response to an external shear stress, we find that additional sources of noise can lead to a fluidisation effect. As we increase the noise intensity we evidence a transition from a non-monotonic to a monotonic rheology, associated with giant fluctuations of the macroscopic shear rate and long-time correlated dynamics. Although distinct noise models can lead to different rheological behaviours in the low stress regime, we show that the noise-induced transition from shear-localised to homogeneous flow at higher stresses appears very generic. The observed dynamical features can be interpreted as a result of an out-of-equilibrium phase transition, for which we estimate the critical exponents that appear to be independent of the specific choice of the noise implementation for the microscopic dynamics.
Highlights
Dense disordered materials such as emulsions, foams, colloidal suspensions, or granular materials exhibit rich rheological behaviours
We studied two models of a fluidising noise leading to a transition between a self-fluidised regime and an externally fluidised regime in the flow of soft glassy materials
Upon increase of the external noise amplitude we evidence the vanishing of shear bands, which is an indication of a transition from an unstable shearlocalised flow to a stable homogeneous flow
Summary
Dense disordered materials such as emulsions, foams, colloidal suspensions, or granular materials exhibit rich rheological behaviours. The steady state flow behaviour of these yield stress fluids (YSF) can be described at the continuum level using empirical laws such as the Herschel-Bulkley relationship [3], or continuum descriptions, such as visco-elasto-plastic [4, 5] and fluidity models [6, 7] While such descriptions account well for the average flow behaviour at a coarse grained scale, it has appeared that some flow features of YSF are dominated by giant fluctuations of the relevant rheological quantities on the macroscopic scale [8,9,10,11]. This leads to non-monotonic rheological constitutive curves [7, 20, 21], that can be associated with flow instabili- Besides this self-generated mechanical noise there can be additional external sources of noise, which can be regarded as a first approximation as independent of the shear-induced one. This suggests that this type of transition might be very generic, independent of the microscopic details in the underlying dynamics
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