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- Title
A numerical study of suspension of microdroplets in a channel under uniform electric field at finite electric Reynolds numbers, Melcher–Taylor theory revisited.
- Authors
Mortazavi, S.; Zahedi, R.
- Abstract
The flow of emulsions under the action of an electric field has practical applications in microfluidic systems such as lab-on-a-chip devices. An emulsion of drops under uniform electric field is studied by numerical simulations. The familiar finite difference front tracking method is used to simulate the two-phase medium. The flow is studied at finite electric Reynolds numbers. In case of finite inertia, density appears as an important parameter that affects the behavior of the flow. Two- and three-dimensional systems have been studied in the present work. The full equation for conservation of charge has been applied in the numerical method. The drop deformation and shape agree with Taylor's leaky dielectric theory in the limit of small electric Reynolds number (Re2). However, the drop deformation deviates from the theory at relatively large electric Reynolds numbers, specifically the drop turns to a prolate shape instead of an oblate shape. It is found that emulsions of two-dimensional drops concentrate in the wall regions at small electric Reynolds numbers where drops have an oblate shape. The bond between drops become strong and it becomes difficult to break fibers when the Reynolds number based on the fluid density is raised (Re1). The increase in Reynolds number (Re1) reduces the actual flow rate inside the channel. At large Reynolds numbers (Re1) and relatively high capillary numbers, oblate drops form clusters at the center of the channel with size of the same order as the channel height in three-dimensional flow. At large electric Reynolds numbers (Re2), drops become prolate and form stable fibers across the channel. This reduces the net flow rate substantially. The net flow also decreases as the electric Reynolds number is raised (Re2).
- Subjects
REYNOLDS number; ELECTRIC fields; FINITE fields; THREE-dimensional flow; MICRODROPLETS; SPHEROIDAL state; ELECTRORHEOLOGY
- Publication
Archive of Applied Mechanics, 2022, Vol 92, Issue 12, p4033
- ISSN
0939-1533
- Publication type
Article
- DOI
10.1007/s00419-022-02280-5