scholarly journals Electric field-induced pinch-off of a compound droplet in Poiseuille flow

2019 ◽  
Vol 31 (6) ◽  
pp. 062004 ◽  
Author(s):  
Somnath Santra ◽  
Sayan Das ◽  
Suman Chakraborty
Keyword(s):  
Electric Field ◽  
Poiseuille Flow ◽  
Compound Droplet

Dynamics of a compound droplet under the combined influence of electric field and shear flow

2021 ◽  
Vol 6 (2) ◽  
Author(s):  
Manash Pratim Borthakur ◽  
Binita Nath ◽  
Gautam Biswas
Keyword(s):  
Shear Flow ◽  
Electric Field ◽  
Compound Droplet

Using Shear and DC Electric Fields to Manipulate and Self-Assemble Dielectric Particles on Microchannel Walls

2014 ◽  
Author(s):  
Minami Yoda ◽  
Necmettin Cevheri
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Poiseuille Flow ◽  
Lift Force ◽  
Colloidal Particles ◽  
Solid Surfaces ◽  
Electric Field Magnitude ◽  
Field Magnitude ◽  
Combined Flow ◽  
Lift Forces

Manipulating suspended neutrally buoyant colloidal particles of radii a = O(0.1 μm–1 μm) near solid surfaces, or walls, is a key technology in various microfluidics devices. These particles, suspended in an aqueous solution at rest near a solid surface, or wall, are subject to wall-normal “lift” forces described by the DLVO theory of colloid science. The particles experience additional lift forces, however, when suspended in a flowing solution. A fundamental understanding of such lift forces could therefore lead to new methods for the transport and self-assembly of particles near and on solid surfaces. Various studies have reported repulsive electroviscous and hydrodynamic lift forces on colloidal particles in Poiseuille flow (with a constant shear rate γ̇ near the wall) driven by a pressure gradient. A few studies have also observed repulsive dielectrophoretic-like lift forces in electroosmotic (EO) flows driven by electric fields. Recently, evanescent-wave particle tracking has been used to quantify near-wall lift forces on a = 125 nm–245 nm polystyrene (PS) particles suspended in a monovalent electrolyte solution in EO flow, Poiseuille flow, and combined Poiseuille and EO flow through ∼30 μm deep fused-silica channels. In Poiseuille flow, the repulsive lift force appears to be proportional to γ̇, a scaling consistent with hydrodynamic, vs. electroviscous, lift. In combined Poiseuille and EO flow, the lift forces can be repulsive or attractive, depending upon whether the EO flow is in the same or opposite direction as the Poiseuille flow, respectively. The magnitude of the force appears to be proportional to the electric field magnitude. Moreover, the force in combined flow exceeds the sum of the forces observed in EO flow for the same electric field or in Poiseuille flow for the same γ̇. Initial results also imply that this force, when repulsive, scales as γ̇1/2. These results suggest that the lift force in combined flow is fundamentally different from electroviscous, hydrodynamic, or dielectrophoretic-like lift. Moreover, for the case when the EO flow opposes the Poiseuille flow, the particles self-assemble into dense stable periodic streamwise bands with an average width of ∼6 μm and a spacing of 2–4 times the band width when the electric field magnitude exceeds a threshold value. These results are described and reviewed here.

Using Shear and Direct Current Electric Fields to Manipulate and Self-Assemble Dielectric Particles on Microchannel Walls

2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Necmettin Cevheri ◽  
Minami Yoda
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Poiseuille Flow ◽  
Lift Force ◽  
Colloidal Particles ◽  
Solid Surfaces ◽  
Electric Field Magnitude ◽  
Field Magnitude ◽  
Combined Flow ◽  
Lift Forces

Manipulating suspended neutrally buoyant colloidal particles of radii a = O (0.1–1 μm) near solid surfaces, or walls, is a key technology in various microfluidics devices. These particles, suspended in an aqueous solution at rest near a solid surface, or wall, are subject to wall-normal “lift” forces described by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory of colloid science. The particles experience additional lift forces, however, when suspended in a flowing solution. A fundamental understanding of such lift forces could therefore lead to new methods for the transport and self-assembly of particles near and on solid surfaces. Various studies have reported repulsive electroviscous and hydrodynamic lift forces on colloidal particles in Poiseuille flow (with a constant shear rate γ· near the wall) driven by a pressure gradient. A few studies have also observed repulsive dielectrophoretic-like lift forces in electroosmotic (EO) flows driven by electric fields. Recently, evanescent-wave particle tracking has been used to quantify near-wall lift forces on a = 125–245 nm polystyrene (PS) particles suspended in a monovalent electrolyte solution in EO flow, Poiseuille flow, and combined Poiseuille and EO flow through ∼30 μm deep fused-silica channels. In Poiseuille flow, the repulsive lift force appears to be proportional to γ·, a scaling consistent with hydrodynamic, versus electroviscous, lift. In combined Poiseuille and EO flow, the lift forces can be repulsive or attractive, depending upon whether the EO flow is in the same or opposite direction as the Poiseuille flow, respectively. The magnitude of the force appears to be proportional to the electric field magnitude. Moreover, the force in combined flow exceeds the sum of the forces observed in EO flow for the same electric field and in Poiseuille flow for the same γ·. Initial results also imply that this force, when repulsive, scales as γ·1/2. These results suggest that the lift force in combined flow is fundamentally different from electroviscous, hydrodynamic, or dielectrophoretic-like lift. Moreover, for the case when the EO flow opposes the Poiseuille flow, the particles self-assemble into dense stable periodic streamwise bands with an average width of ∼6 μm and a spacing of 2–4 times the band width when the electric field magnitude exceeds a threshold value. These results are described and reviewed here.

Effect of nonuniform electric field on the electrohydrodynamic motion of a drop in Poiseuille flow

2017 ◽  
Vol 29 (5) ◽  
pp. 052006 ◽  
Author(s):  
Shubhadeep Mandal ◽  
Suryapratim Chakrabarti ◽  
Suman Chakraborty
Keyword(s):  
Electric Field ◽  
Poiseuille Flow ◽  
Nonuniform Electric Field

Compound‐Droplet‐Pairs‐Filled Hydrogel Microfiber for Electric‐Field‐Induced Selective Release

Small ◽  
2019 ◽  
Vol 15 (42) ◽  
pp. 1903098 ◽  
Author(s):  
Xiaokang Deng ◽  
Yukun Ren ◽  
Likai Hou ◽  
Weiyu Liu ◽  
Tianyi Jiang ◽  
...  
Keyword(s):  
Electric Field ◽  
Compound Droplet

scholarly journals Modal and non-modal stability analysis of electrohydrodynamic flow with and without cross-flow

2015 ◽  
Vol 770 ◽  
pp. 319-349 ◽  
Author(s):  
Mengqi Zhang ◽  
Fulvio Martinelli ◽  
Jian Wu ◽  
Peter J. Schmid ◽  
Maurizio Quadrio
Keyword(s):  
Stability Analysis ◽  
Electric Field ◽  
Linear Stability ◽  
Poiseuille Flow ◽  
Cross Flow ◽  
Transient Growth ◽  
Unstable Flow ◽  
Electrohydrodynamic Flow ◽  
Stability Threshold ◽  
Energy Growth

We report the results of a complete modal and non-modal linear stability analysis of the electrohydrodynamic flow for the problem of electroconvection in the strong-injection region. Convective cells are formed by the Coulomb force in an insulating liquid residing between two plane electrodes subject to unipolar injection. Besides pure electroconvection, we also consider the case where a cross-flow is present, generated by a streamwise pressure gradient, in the form of a laminar Poiseuille flow. The effect of charge diffusion, often neglected in previous linear stability analyses, is included in the present study and a transient growth analysis, rarely considered in electrohydrodynamics, is carried out. In the case without cross-flow, a non-zero charge diffusion leads to a lower linear stability threshold and thus to a more unstable flow. The transient growth, though enhanced by increasing charge diffusion, remains small and hence cannot fully account for the discrepancy of the linear stability threshold between theoretical and experimental results. When a cross-flow is present, increasing the strength of the electric field in the high-$\mathit{Re}$Poiseuille flow yields a more unstable flow in both modal and non-modal stability analyses. Even though the energy analysis and the input–output analysis both indicate that the energy growth directly related to the electric field is small, the electric effect enhances the lift-up mechanism. The symmetry of channel flow with respect to the centreline is broken due to the additional electric field acting in the wall-normal direction. As a result, the centres of the streamwise rolls are shifted towards the injector electrode, and the optimal spanwise wavenumber achieving maximum transient energy growth increases with the strength of the electric field.

The effect of uniform electric field on the cross-stream migration of a drop in plane Poiseuille flow

2016 ◽  
Vol 809 ◽  
pp. 726-774 ◽  
Author(s):  
Shubhadeep Mandal ◽  
Aditya Bandopadhyay ◽  
Suman Chakraborty
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Numerical Simulations ◽  
Poiseuille Flow ◽  
Shape Deformation ◽  
Uniform Electric Field ◽  
Plane Poiseuille Flow ◽  
Stream Migration ◽  
The Cross ◽  
Transverse Position

The effect of a uniform electric field on the motion of a drop in an unbounded plane Poiseuille flow is studied analytically. The drop and suspending media are considered to be Newtonian and leaky dielectric. We solve for the two-way coupled electric and flow fields analytically by using a double asymptotic expansion for small charge convection and small shape deformation. We obtain two important mechanisms of cross-stream migration of the drop: (i) shape deformation and (ii) charge convection. The second one is a new source of cross-stream migration of the drop in plane Poiseuille flow which is due to an asymmetric charge distribution on the drop surface. Our study reveals that charge convection can cause a spherical non-deformable drop to migrate in the cross-stream direction. The combined effect of charge convection and shape deformation significantly alters the drop velocity, drop trajectory and steady state transverse position of the drop. We predict that, depending on the orientation of the applied uniform electric field and the relevant drop/medium electrohydrodynamic parameters, the drop may migrate either towards the centreline of the flow or away from it. We obtain that the final steady state transverse position of the drop is independent of its initial transverse position in the flow field. Most interestingly, we show that the drop can settle in an off-centreline steady state transverse position. Two-dimensional numerical simulations are also performed to study the drop motion in the combined presence of plane Poiseuille flow and a tilted electric field. The drop trajectory and steady state transverse position of the drop obtained from numerical simulations are in qualitative agreement with the analytical results.

Evolution of a compound droplet attached to a core-shell nozzle under the action of a strong electric field

2006 ◽  
Vol 18 (6) ◽  
pp. 062101 ◽  
Author(s):  
S. N. Reznik ◽  
A. L. Yarin ◽  
E. Zussman ◽  
L. Bercovici
Keyword(s):  
Electric Field ◽  
Strong Electric Field ◽  
Core Shell ◽  
Compound Droplet

Cross-stream migration of drops suspended in Poiseuille flow in the presence of an electric field

2018 ◽  
Vol 97 (6) ◽  
Author(s):  
Binita Nath ◽  
Gautam Biswas ◽  
Amaresh Dalal ◽  
Kirti Chandra Sahu
Keyword(s):  
Electric Field ◽  
Poiseuille Flow ◽  
Stream Migration
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