Drop rise velocities and fluid dynamic behavior in standard test systems for liquid/liquid extraction-experimental and numerical investigations

The fluid dynamic behavior of single organic droplets rising in a quiescent ambient liquid is investigated experimentally and numerically. Three standard test systems for liquid/liquid extraction recommended by the European Federation of Chemical Engineering (EFCE) but without the respective transfer component have been chosen for the investigations: toluene/water, n-butyl acetate/water, and n-butanol/water, representing systems with high, medium, and low interfacial tension. Simulations are performed using the academic code Navier, which features a sharp interface representation and a variational formulation of the curvature. The validity of both correlations and the results obtained by dynamic numerical simulation is discussed in terms of terminal rise velocity, aspect ratio, and the onset of shape oscillation. The numerical results show excellent agreement with experiments in all three test systems, and with simulations in the n-butanol/water system published recently by Bertakis et al. (2010). The presented numerical method is applicable for a wide range of interfacial tension, whereas the investigated correlations lose accuracy with decreasing interfacial tension.