(331b) Effect of Perturbation Wavelength On Jets of Complex Fluids

A liquid jet can become unstable and break up into drops as a result of undulations on its surface. The effect of these undulations in the jet breakup process, particularly on crucial features such as drop size and drop size distribution, is of broad scientific interest, and of particular interest to those studying spray and propulsion systems. Due to the widespread industrial use of complex fluids, including surfactant and polymeric solutions, recent studies have focused on the breakup of surfactant laden jets or non-Newtonian liquid jets, but modeling of the two subjects proceed more or less independently and little is known about their coupled effect on jets. Here we present direct numerical simulations showing that combined surfactant and non-Newtonian effects can result in a threshold value for the undulation wavelength above which the system makes a sudden transition to a new, different behavior with a much different drop size distribution. Since direct simulations of the free-surface system of governing equations, including fully coupled continuity, momentum and surfactant convection-diffusion equation, enabled a comprehensive analysis of the physical effect of perturbation wavelength on the breakup dynamics of jets of complex liquids, results from this study can have a significant impact on the more rational design of surfactant and polymer additives for spray and propulsion systems.