Impact of spatially heterogeneous electric fields on the ascent of a solitary bubble in various confinements

This study investigates the electrohydrodynamic manipulation of solitary bubble trajectories in confined rectangular channels using spatially varying electric fields generated by segmented electrode configurations. A comprehensive numerical solver was developed by integrating complete charge conservation equations and the piecewise linear interface reconstruction method into the OpenFOAM framework, enabling accurate capture of coupled fluid dynamics and electrohydrodynamic phenomena. Bubbles maintaining straight vertical trajectories under uniform electric fields undergo substantial variations in path under spatially varied fields. Systematic parametric analysis across three confinement ratios (CR = 0.15, 0.2, 0.3), four electrode lengths (L* = 2, 3, 4), four gap spacings (G* = 2, 3, 4, 5), and four electric capillary numbers (CaE = 1, 2, 3, 5) reveals that spatially varying electric fields transform stable vertical bubble rise into complex zigzag motion patterns. Analysis examines electric field lines, vorticity fields, and electric force vectors. Trajectory characterization involves four key parameters: maximum linear X deviation, relative path complexity, maximum amplitude, and regime classification. Results show that the electric capillary number emerges as the primary control parameter, increasing trajectory path complexity by 20%–25% and maximum amplitudes up to five times. The confinement ratio acts as a fundamental scaling parameter, with narrow channels (CR = 0.3) achieving maximum amplitudes compared to wide channels. The electric field line distribution shows that electrode length affects forcing duration, while gap spacing determines gradient steepness. These geometric parameters establish a hierarchy (CaE > CR > G* > L*) enabling predictive design of electrohydrodynamic manipulation systems for industrial applications in mixing enhancement.