Influence of electric field on deformation of a drop in shear flow

Abstract

The dynamics of a droplet in shear flow under the influence of an external electric field are investigated by performing extensive numerical simulations. The study is carried out by solving two-dimensional electrohydrodynamic equations, and the interface is captured using a volume-of-fluid approach. It is observed that with an increase in the drop size, a confined drop exhibits enhanced deformation and preferred orientation with the flow direction. For the case of dielectric fluids, the deformation of the drops can be either enhanced or reduced by varying the permittivity ratio and electric field strength. The nature of the polarisation forces acting at the interface can be either compressive or tensile depending on the magnitude of the permittivity ratio. The local electric field intensity inside the drop is significantly altered due to the permittivity contrast between the fluids. The computations for leaky dielectric fluids reveal that the deformation of the drop can be effectively tuned by altering the permittivity as well as the conductivity ratios. The nature of charge accumulation and the electric forces acting at the interface are critically dependent on the relative contrast between the electric properties of both the phases. The conductivity ratio decides the magnitude and nature of charge at the upper and lower portions of the droplet interface, thereby fundamentally maneuvering the droplet dynamics under the applied electric field.