Large eddy simulation of droplet breakup in turbulent flow with adaptive mesh refinement

The interaction between droplets of different scales and turbulent flow is investigated with numerical simulations. To capture the gas flow characteristics and interface evolution accurately, the large eddy simulation method is combined with adaptive mesh refinement. This numerical strategy is shown to be suitable for complex two-phase flow simulations at moderate costs. The initial sizes of droplets are the characteristic length scales in homogeneous isotropic turbulence. From large to small sizes, the finite-, inertial-, Hinzeand Taylor-scale droplets are set separately in each simulation. Results show that droplets of different initial sizes respond differently to the gas flow. Large droplets present periphery shedding at the initial stage of breakup and tend to be stretched into a disklike shape before final breakup. Small droplets are carried by the gas field and deform into cylindrical structures besides the disklike shape. Pressure perturbations are found in both phases, and the average pressure is increased on the whole. The breakup processes introduce more fine structures in the flow field, and oscillation of the energy spectra in the inertial subrange is observed. Most vorticity vectors are aligned with the second principal axis of strain rate tensor and perpendicular to the third principal axis. The distribution of vortical structures is modified by the existence of droplets, and the unstable flow patterns are found to be enhanced as droplets breakup. The turbulence kinetic energy of the gas phase is suppressed more extensively with the decrease of droplet scale. The simulations provide more insights into the mechanisms of the two-phase interaction under realistic conditions.