Experimental and Numerical Investigation of Electrohydrodynamic Modes of Viscoelastic Polymeric Solutions

The main aim of this study is to explore the role of viscoelastic properties of polymeric solutions on mode transitions in electrospray process. By adjusting the applied electric potential between the nozzle and the collecting substrate, various electrohydrodynamic (EHD) modes were photographed by a high-speed camera. Then, the effect of operating parameters on the drops size in dripping mode and the jet profile in jet mode was investigated. By categorizing the EHD modes of each viscoelastic solution into dimensionless operating maps, it can be seen that by increasing the solution concentration or flowrate, the extents of dripping mode and beads on string structure dwindle, while the jet stabilizes in a wider range of electric capillary numbers. Furthermore, contrary to deionized (DI) water, when the applied voltage escalates, the stick jet mode is observed where the jet sticks to the outer surface of the nozzle, and the asymptotic thickness of the jet falls. In the second part of this research, several numerical simulations were conducted to simulate the behavior of an electrified viscoelastic jet. First, an electrified DI water jet was simulated, and the obtained jet profile was compared to the experimental data. Afterwards, the proposed algorithm was used to simulate viscoelastic electrified jets, where the effect of Weissenberg number (Wi) on the jet profile was examined. In agreement with the experimental results, by increasing the solution concentration, the asymptotic profile of the jet is reached at a smaller length from the nozzle, while the final thickness of the jet is slightly reduced.