Modulation of inter-phase, cross-scale momentum transfer by preferentially-concentrated inertial particles

Decaying homogeneous isotropic turbulence suspended with inertial point particles is investigated for understanding inter-phase, cross-scale interactions. Using a wavelet multiresolution analysis, the cross-scale transfer of turbulence kinetic energy (TKE) is quantified with a good spectral and spatial resolution and characterized as a function of the particle Stokes number $\text{St}_k$. Due to the spatially-local nature of the preferential concentration, the work done by the critical particles ($\text{St}_k = 1$) is increasingly intermittent in space. However, the subfilter-scale energy transfer by the triadic interactions becomes less intermittent than that of the particle-free simulation. Conditioned analysis is performed by evaluating joint probability density function of wavelet statistics. In contrast to the preferential concentration in the one-way coupled simulations, small-scale kinetic energy is positively correlated with the coarse-grained particle-number density where local TKE fluctuations are higher than the average. A collective work done by the high-concentration critical particles amplifies turbulent fluctuations, consistent to the unconditioned wavelet analysis.