Irreversibility and chaos: Role of long-range hydrodynamic interactions in sheared suspensions

Non-Brownian particles suspended in an oscillatory shear flow are studied numerically. In these systems it is often assumed that chaos (due to the long-range nature of the hydrodynamic interaction between particles) plus noise (contact or roughness) lead to irreversible behavior. However, we demonstrate that the long-range hydrodynamic interactions are not a source, nor even a magnifier, of irreversibility when coupled with non-hydrodynamic interactions. Additionally, analysis reveals that the apparent anisotropy of the particle diffusion is due to coupling of the shear flow and transverse diffusion.