Experiments on deformable oil droplets in turbulence

In this work, we experimentally investigate the momentum flux and breakup frequency in low-concentration oil in water mixtures. We use six high-speed cameras to capture the droplets dynamics in homogeneous and isotropic turbulence (HIT). The experiments are done in the TU Wien Jet-Stirred Turbulence Tunnel: two opposite jet arrays generate local HIT with zero-mean flow within an octagonal test section. The Taylor-Reynolds number ranges from 100 to 300, featuring energy dissipation rates of Ο(0.1 m²s^-3). We control the turbulence intensity and the droplets diameter to set the Weber number (We) to Ο(1), while changing the droplets viscosity tunes the Ohnesorge number (Oh) to Ο(0.1–10). Different methyl phenyl silicone oils are used, with the kinematic viscosity ranging from 20 to 3000 cSt; the oils are density-matched with the carrier phase (distilled water). To assess the complex interplay between the two phases, we simultaneously measure the interface shape and the surrounding flow structures. The interface reconstruction is based on the virtual-camera method (Masuk et al. 2019), and flow statistics are obtained via Shake-the-Box. As results, we discuss the 3D reconstruction of the filaments formed before the breakup, how the droplets inner viscosity affects the deformation rate, and how the breakup frequency scales with We/(1+Oh).