Rheology of dense, bidispersed particles suspended in a perturbed shear-flow

We have studied the phenomenon of segregation of a non-Brownian dense suspension (volume fraction φ=0.50) of rigid, inertialess bidispersed particles, with a large particle-size-ratio a₂/a₁=3, being a₁ and a₂ the radii of the smaller and larger particles in the suspension, respectively. The particles have been immersed in a simple shear-flow of a Newtonian-fluid at a vanishing Reynolds number. The shear-rate was fixed to a value that places the rheological response of the suspension in the post-shear-thickening plateau.

To control the variation of the shear-thickening behaviour, we perturbed the underline shear-flow by adding to the velocity vector a simple sinusoidal wave of the form u_i = A sin(k_j x_j), where u_i is the ith velocity component, A is the amplitude of the wave and the pair k_j,x_j are the wavenumber and the spatial coordinate in the jth direction, respectively; the resulting parametric study considers six different scenarios. We select the waves that cause significant modifications to the rheological response and we carry out a parametric study varying the  amplitude and wavenumber. The study has been performed numerically by means of a validated and publicly available software CFF-Ball-0x that tackles the Newton-Euler equations governing the dynamics of the particles.