Fluid dynamics of a double emulsion droplet in an electric field

Abstract

One of general free boundary problems concerning the electrohydrodynamic effects on a concentric double emulsion drop is studied theoretically for the three constituent phases of leaky dielectric fluids. In order to proceed the problem analytically, the domain perturbation procedure is utilized in the small deformation limit. The patterns of electric-field-driven flow are successfully characterized by examining the distribution of induced surface charges at the inner and outer drop interfaces. The second recirculating flow is generated in the annular phase when the inner and outer interfaces are charged with the same sense. The deformation type of inner and outer interfaces can be roughly interpreted by the flow patterns, although the exact description on the deformation requires consideration of the combined contributions from both electric and flow fields. In addition, the presence of double emulsion droplets alters the stress field of the continuous phase. The electric-field-induced ''particle stress'' not only changes the effective viscosity of dispersion of the double emulsion droplets but yields the normal stress difference, which is typical of a viscoelastic fluid. Finally, the heat transfer rate enhanced by the electric-field-driven flow is also considered.

Electrohydrodynamics of a compound drop

“…They also showed qualitatively how the fluid orientation could lead to different senses of fluid flow circulation and drop deformation. Ha and Yang [28] studied the problem analytically in the creeping flow limit and for small deformation. They used a formal solution based on the general form of the solution to Stokes equation (see Refs.…”

Hydrodynamic Interaction between Spheres Coated with Deformable Thin Liquid Films

“…When a quasi-steady deformation approximation is valid, the second-part equations of kinematic conditions [6] and [7] relating the rate of change in h i to the normal component of the velocity are not needed to determine the interface shape. Only, the continuity of velocities at the interface is needed.…”

“…The rate of change of the interface deformation can be determined by converting kinematic conditions [6] and [7] to those based on the moving coordinates with the approaching velocity. It is a simple matter to estimate the rate of change of the coated film thickness relative to that of the sphere position by comparing two independent characteristic timescales; i.e., t film c [15] in which the Reynolds number is defined as…”

“…Initially, droplets are transported to a nearby drop by external mean flow, Brownian motion, or external fields such as gravity (5,6) and electric field (7,8). As the gap between the twodrop surfaces becomes narrower, the fluid in the gap is drained out.…”

Encapsulated Drop Breakup in Shear Flow

“…Previous studies [15,20,21] have analyzed deformation in extensional flow, which tends to stretch the shell while compressing the core. Here we show that shear flow deforms the core in tandem with the outer drop and that new behaviors emerge that have no parallel for simple drops.…”