DNS of fully resolved spherical particles dispersed in isotropic turbulence

Our DNS study concerns the interactions between decaying isotropic turbulence and solid spherical particles with diameter, $d$, larger than the Kolmogorov length scale, $\eta$. We employ an Immersed Boundary method similar to that of Uhlmann (JCP, 2005) to resolve the flow around $6400$ spherical particles with a volume fraction of $\phi_v=0.1$. The monosize particles have a diameter, $d = 16 \eta_o$. Our simulations, with $256^3$ mesh points and $Re_{\lambda_0} = 75$, cover a range of $38 \le \tau_p/\tau_{K_o} \le 149$, for the ratio of the particle response time to the initial Kolmogorov time scale. A Lagrangian approach is used to compute the frequency spectrum of the turbulence kinetic energy (TKE) of the fluid phase. The effects of varying $\tau_p/\tau_{K_o}$ on the spectrum and the decay rate of TKE are discussed. The effects of the formation of the particle boundary layer on the viscous dissipation rate of TKE are also discussed.