  Dense non-Brownian suspensions exhibit significant shear thinning, although a
comprehensive understanding of the full scope of this phenomenon remains
elusive. This study numerically reveals intimate heterogenous coupled dynamics
between many-body particle motions and solvent hydrodynamics in shear-thinning
non-Brownian suspensions. We demonstrate the spatially correlated viscous
dissipation and particle motions; they share the same characteristic length,
which decreases with increasing shear rate. We further show that, at lower
shear rates, significant particle density changes are induced against the
incompressibility of the solvent, suggesting the cooperative creation and
annihilation of gaps and flow channels. We discuss that hydrodynamic
interactions may substantially restrict particle rearrangements even in highly
dense suspensions, influencing the quantitative aspects of macroscopic
rheology.
