Improved numerical model for high-resolution electrohydrodynamic jet printing

Detailed numerical simulations of the electrohydrodynamic (EHD) printing process provide valuable insights into the underlying highly transient phenomena that are difficult to observe experimentally as they involve various length- and time-scales. This study presents an improved numerical approach for accurately simulating axisymmetric EHD printing processes with a focus on eliminating nonphysical charge leakage. Three primary sources of charge leakage are identified and addressed, i.e., numerical diffusion at the interface, averaging of electrical properties near the interface and spurious currents. Charge compression is introduced as the most effective mitigation strategy to counteract numerically induced charge leakage. Interface curvature is calculated based on the piecewise linear interface calculation with reconstruction distance function (plicRDF) method, achieving errors below 1%. Furthermore, the maximum velocity magnitude of spurious currents is reduced by three orders of magnitude compared to the standard curvature calculation used in interFoam. Dynamic meshing and load balancing are employed to enhance computational efficiency, outperforming graded grid approaches commonly used in the context of EHD printing simulations. Spatial accuracy of the numerical solutions is evaluated by a grid convergence study, which demonstrates that for an accurate prediction of the investigated EHD printing process, the smallest computational-cell sizes need to be an order of magnitude smaller than those used in prior studies. Simulation results based on the present model show good agreement with experiments conducted by the authors and with experimental data from literature sources. In addition, present solutions are in better agreement with experimental observations than numerical results reported by others for the same case.