Electrohydrodynamic interaction between droplet pairs in a confined shear flow

Abstract

The present study deals with the numerical as well as asymptotic analysis of the electrohydrodynamic interaction between two deformable droplets in a confined shear flow. Considering both the phases as leaky dielectric, we have performed numerical simulations to study the effect of channel confinement on the drop trajectories in the presence of a uniform electric field. Two important varieties of motion are identified in the present analysis, namely (i) the reversing motion and (ii) the passing over motion. The study suggests that conversion of the passing over motion to the reversing motion or vice versa is possible via modulating the strength of the imposed electric field. Such a conversion of the pattern of droplet migration is also possible in a confined domain due to change in different electrical properties of the system (for instance conductivity). The present numerical model is also able to predict the pattern of the trajectory of individual droplets depending on the initial distance separating the two. For example, a smaller initial distance results in a reversing motion whereas a passing over motion is predicted when the distance between the droplets is significantly large. However, the final positions of the droplets are found to be independent of their initial positions. Interestingly, presence of electric field is found to prevent droplet coalescence to a certain extent depending on its strength, thus rendering the emulsion stable. A small deformation asymptotic model is also developed under the assumption of negligible fluid inertia to support the numerical results for the limiting case of an unbounded flow. The current investigation successfully presents a novel technique to predict the precise positions of a system of droplets in a micro-channel and how electric field can be used as a tool to modulate droplet trajectories in an emulsion. Such a study has a wide potential towards application in design and functionalities of several modern-day droplet based micro fluidics devices.

Steady axial electric field may lead to controllable cross-stream migration of droplets in confined oscillatory microflows

“…The boundary conditions employed at the top and bottom walls ( B T and B B ) in dimensionless forms read Here, denotes the normal vector at the walls. The governing equations have been solved using the finite element method taking the mentioned boundary conditions into consideration (Mandal et al 2015 b ; Santra et al 2019 b ; Wang et al 2019). The details of the numerical implementation are described in the supplementary material available at .…”

Electrically modulated dynamics of a compound droplet in a confined microfluidic environment

“…The order parameter is regulated by the Cahn–Hilliard equation in the following form (Santra et al. 2019 b ) The non-dimensional quantities in (2.16) are , which is the non-dimensional chemical potential, where is the Cahn number, which controls the interface thickness. Another important non-dimensional parameter is the Péclet number denoted as (the ratio of convective and diffusive transport of the phase field order parameter).…”

“…At the interface, the value of ψ(x, t) varies from −1 to +1 rapidly. The order parameter ψ(x, t) is regulated by the Cahn-Hilliard equation in the following form (Santra et al 2019b)…”

The Influence of Forced Convective Heat Transfer on Hybrid Nanofluid Flow in a Heat Exchanger with Elliptical Corrugated Tubes: Numerical Analyses and Optimization

“…The significance of the thermal and flow characteristics of nanofluids has been reported. Santra et al [29] carried out a study focusing on the thermohydraulic characteristics of Cu-water NFs inside a plain horizontal channel by influencing the intensity of the electric field and volume fraction (VF) of nanoparticles (NPs). They discovered that when the volume percentage of NPs and the Reynolds number (Re) increase, heat flow improves.…”