Universal Scaling Laws or Dense Particle Suspensions in Turbulent Wall-Bounded Flows

We examine by means of large-scale interface-resolved numerical simulations the macroscopic behavior of dense suspensions of neutrally-buoyant spheres in turbulent plane channel flow. We show that particles larger than the smallest turbulence scales cause the suspension to deviate from the continuum limit in which its dynamics is well described by an effective suspension viscosity. This deviation is caused by the formation of a particle layer close to the wall with significant slip velocity. By assuming two distinct transport mechanisms in the near-wall layer and the turbulence in the bulk, we propose scaling laws for the mean velocity profile of the suspension, together with a master equation able to predict the drag as function of the particle size and volume fraction.

References: 

P. Costa, F. Picano, L. Brandt and W.-P. Breugem, Physical Review Letters, 117, 134501, 2016.