Impact of Marangoni instabilities on the fluid dynamic behaviour of organic droplets

Marangoni instabilities in dispersed liquid/liquid systems occur if the local solute concentration varies over the interface. The additional shear stress at the interface between a droplet and an ambient phase generates complex convection patterns which increase temporarily the global drag coefficient of the drop and thus retard the drop rise velocity. When Marangoni effects get weaker, the shear forces decrease and the drop reaccelerates. In the present experimental study, the transient drop rise velocity has been intensely investigated in the system toluene(d)/acetone(s)/water(c) for different initial solute concentrations and different drop diameters. Both mass transfer directions have been considered. The reacceleration time as an indicator of the end of Marangoni dominance can be expressed as a function of drop diameter and initial solute concentration.