Modulation of isotropic turbulence by deformable droplets of Taylor lengthscale size

We investigate the effects of finite-size deformable droplets on decaying isotropic turbulence via direct numerical simulation (DNS). DNS is performed using the two-fluid pressure-correction method by Dodd and Ferrante [\emph{J. Comput. Phys.} \textbf{273} (2014) 416--434] coupled with the volume of fluid method by Baraldi et al. [\emph{Comput. \& Fluids} \textbf{96} (2014) 322--337]. We fully-resolve the flow around and inside 3130 droplets of Taylor lengthscale size, resulting in a droplet volume fraction of 0.05. The initial Taylor lengthscale Reynolds number is Re$_{\lambda0}=75$, and the computational mesh has $1024^3$ grid points. We analyze the effects on turbulence modulation of varying the droplet- to carrier-fluid viscosity ratio ($1 \leq \mu_d/\mu_c \leq 100$) and the droplet Weber number based on the r.m.s velocity of turbulence ($0.1 \leq \mathrm{We}_{rms} \leq 5$). We discuss how varying these parameters affects the turbulence kinetic energy budget, and explain the physical mechanisms for such modulation.