Fully resolved DNS of freely moving finite-size particles in decaying isotropic turbulence

The objective of the present study is to investigate the two-way coupling effects of freely moving {\em finite-size} solid particles on decaying isotropic turbulence. The particle diameter is of the order of the Taylor micro- scale of turbulence, $\lambda$, i.e. $d\sim\lambda > \eta$, and the volume fraction of particles $\phi_v\sim 0.1$. Our DNS employs an {\em immersed boundary method} to resolve the flow around each individual particle while simultaneously resolving the fluid motion at the Kolmogorov scale. The Navier-Stokes equations are solved throughout the whole domain (including the volumes occupied by the particles) on a Cartesian mesh. The number of the dispersed particles is $88$ for $ \phi_v=0.01$, and $884$ for $\phi_v=0.1$. The density of the solid particles is 2.56 times that of the carrier fluid. The modifications of the decay rate and the spectrum of the turbulence kinetic energy and its dissipation rate are discussed.