Numerical investigation of electric field effect on interface instability and deformation

Understanding the effect of an electric field on a sharp interface separating two different fluids or phases is critical to many applications, including environmental remediation, water purification, and inkjet printing. In this study, the interfacial instability and deformation under a vertical or horizontal DC electric field are studied through detailed numerical simulations using the open-source solver Basilisk. The sharp interface is resolved by the volume-of-fluid method, and the adaptive mesh refinement technique is used to focus high mesh resolution to accurately resolve the interfacial dynamics. The electric stresses are incorporated using the Taylor–Melcher leaky dielectric model, and the height-function method is used to accurately estimate the interfacial curvature required for surface tension calculation. Since the interaction between surface tension and electrical forces dictates the interface deformation, the electric capillary number, which measures the ratio between the two, is the dominant parameter. We consider both a single-mode interfacial wave on a flat surface and the oscillation of a sessile drop with a dynamic contact line. Parametric studies are performed by systematically varying the electric capillary number, permittivity, conductivity, and density ratios. Particular attention is focused on the effects of these parameters on the frequencies of the interfacial wave and the oscillating sessile drop. For the sessile drop, we also investigate the impact of contact line mobility on contact line dissipation, oscillation frequency, and damping rate, with and without the electric field.