Molecular Dynamics Simulations of the Electrocoalescence Behaviors of Two Unequally Sized Conducting Droplets

Abstract

The electrocoalescence of droplets plays a crucial role in various fields. However, studies on the effects of droplet radius on the electrocoalescence behaviors of droplets have not been conducted until now. In this work, the electrocoalescence behaviors of two unequally sized conducting droplets are investigated via molecular dynamics (MD) simulations. The influences of electric field strength and droplet radius on the electrocoalescence behaviors of two unequally sized droplets are investigated. When the electric field strength increases, the contact cone angle between the droplets increases, and the two droplets are more likely to partially coalesce and bounce. When the radius of the smaller droplet between the two droplets increases at the same electric field strength, the contact cone angle, daughter droplet size, and ions in the daughter droplet increase, whereas the critical electric field strength (E d ) for generating the daughter droplet decreases. Furthermore, the daughter droplet is ejected from the smaller droplet when the two droplets have different radii.

Microfluidic Study of the Electrocoalescence of Aqueous Droplets in Crude Oil

“…We begin with a brief review. Electrocoalescence of an isolated pair of droplets of water in a continuous oil under a uniform applied electric field, Figure , has been studied theoretically ,− and experimentally. − ,,− The electrohydrodynamic forces, which cause the droplets to merge in the direction of the field, have been described by the field-induced charge distribution on the surface of the droplets. For an isolated spherical water droplet of radius a placed in a uniform oscillating field ( E̅ e i ω t where E̅ is the amplitude, t is the time, and ω is the frequency), mobile ions in the water and possibly oil phases are conducted in the field direction.…”

“…As relatively spherical droplets approach ( E c ≪ 1) one another, the electric field exerted on the facing poles intensifies, and pronounced opposing prolate deformations develop that precede coalescence. These deformations have been examined theoretically by accounting for interface deformation in continuum computational simulations − and molecular dynamics simulations …”

“…These deformations have been examined theoretically by accounting for interface deformation in continuum computational simulations 61−66 and molecular dynamics simulations. 68 The final stages in the electrocoalescence process have also been visualized in small fluidic cells or microfluidic arrangements in which, in a continuous oil phase, an electric field is applied across free aqueous droplet pairs along their line of centers 70−74 or anchored droplets at a fixed potential difference are arranged to face one another. 75,87−94 The dynamics are visualized over a time interval of hundreds of milliseconds from an initial separation distance s o /a.…”

Molecular Dynamics Study on the Demulsification Mechanism of Water-In-Oil Emulsion with SDS Surfactant under a DC Electric Field

“…Molecular dynamics (MD) simulation is an effective method which is well suited for investigating some physical phenomena on a microscale, for example, molecular adsorption and droplet coalescence . For the case of W/O emulsion, many studies have emerged to explore the microscopic mechanisms of deformation, breakup, and coalescence of water droplets under external electric fields at the molecular level by MD simulation in recent years. − These works mainly focused on the different influencing factors, such as electric field strength, − electric field type, − ion concentration. ,, However, to the best of our knowledge, studies on the electrocoalescence of surfactant-stabilized water droplets using MD method are still rare. Li et al investigated the deformation and breakup mechanism of a single water droplet in acidic crude oil emulsion under uniform electric field.…”

Free Energy and Dynamics of Organic-Coated Water Droplet Coalescence

“…Simulations on pure water droplet coalescence in the gas phase − or on a super-hydrophobic surface to examine the coalescence-induced jumping were carried out. , Recently, our group has just studied the thermodynamics and dynamics of coalescence of pure water droplets . In addition to the case of pure water droplets, MD simulation studies on the coalescence of metal nanodroplets − and electrocoalescence of conducting droplets − were also reported.…”