3D experimental study of droplet deformation and breakup in HIT

We investigate the deformation and breakup mechanisms of oil droplets dispersed in homogeneous isotropic turbulence. The turbulence is created in an octagonal horizontal water tank by a pair of opposite jet arrays, producing an energy dissipation rate of 0.1 [m2 s−3] and Reλ = 550. Five high-speed cameras are used to capture the droplets interface dynamics and the surrounding turbulent field, the latter is obtained by 3D-Particle Tracking Velocimetry (Shake-The-Box). The tested oil has nearly the same density as water but its viscosity is about 30 times higher, and we controlled the turbulence intensity to maintain the Weber number close to unity. Under these conditions, droplets undergo deformation driven by turbulent forcing and, depending on the force balance, either return to a nearly spherical shape or break up. The breakup regime is characterized by significant filament-like elongation due to the droplet high inner viscosity. We provide experimental data demonstrating how the correlation between external turbulence, interfacial tension forcing and internal viscous damping governs the interface dynamics. Furthermore, we discuss the filament-stretching mechanisms and their characteristic timescales, which are essential for developing an accurate droplet population model.