Fragmentation in turbulence revisited – Design of a homogeneous isotropic turbulence experiment for droplet breakup

The present study gives an overview on the preliminary experiments and design of a test rig for sustained homogeneous isotropic turbulence (HIT) with zero mean flow to study turbulent fragmentation of droplets in liquid-liquid flows of similar density. The design follows the concept of randomly actuated synthetic jet arrays (RASJA) to generate a region of HIT that extends several integral length scales. For the fragmentation of bubbles and droplets, the injected initial size needs to be larger than the Kolmogorov-Hinze scale. Hence, there are additional constraints for multiphase experiments in HIT that we discuss, including the initial droplet generation and characteristic time-scales involved in the turbulent fragmentation. The latter entails experimental quantification of the turbulence decay time-scale with distance from the jet arrays, as well as the residence time of the dispersed phase in the HIT region to ensure a sustained fragmentation cascade.