Turbulence modulation in heavy-loaded suspensions of tiny particles

The features of turbulence modulation produced by a heavy lo aded suspension of small solid particles or liquid droplets are discussed by using a physic ally-based regularisation of particle-fluid interactions. The approach allows a robust description of t he small scale properties of the system exploiting the convergence of the statistics with respect t o the regularisation parameter. It is shown that sub-Kolmogorov particles/droplets modify the e nergy spectrum leading to a scaling law, E ( k ) ∝ k − 4 , that emerges at small scales where the particle forcing bal ances the viscous dissipation. This regime is confirmed by Direct Numerical Si mulation data of a particle-laden statistically steady homogeneous shear flow, demonstratin g the ability of the regularised model to capture the relevant small-scale physics. The energy budge t in spectral space, extended to account for the inter-phase momentum exchange, highlights how the p article provide an energy sink in the production range that turns into a source at small scales. Ov erall, the dissipative fluid-particle interaction is found to stall the energy cascade processes t ypical of Newtonian turbulent flows. In terms of particle statistics, clustering at small scale is d epleted, with potential consequences for collision models