Universal scaling laws for the disintegration of electrified drops

Collins, Robert T.; Sambath, Krishnaraj; Harris, Michael T.; Basaran, Osman A.

doi:10.1073/pnas.1213708110

Cited by 167 publications

(191 citation statements)

References 45 publications

Supporting

Mentioning

178

Contrasting

Order By: Relevance

“…Currently, we are extending the idea of decomposing the flow field as the addition of two simpler velocity fields to those cases in which the Reynolds number of the outer stream is large. The same type of ideas based on the slender body approach could also be applied to describe the stability of electrohydrodynamic tip streaming regimes that, under appropriate conditions, take place when electrical stresses act on the interface of liquid threads with a cone-jet structure (Fernandez de la Mora & Loscertales 1994; Barrero & Loscertales 2007;Collins et al 2008Collins et al , 2013. …”

Section: Discussionmentioning

confidence: 99%

Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

2013

View full text Add to dashboard Cite

In this paper we reveal the physics underlaying the conditions needed for the generation of emulsions composed of uniformly sized drops of micrometric or submicrometric diameters when two immiscible streams flow in parallel under the so-called tip streaming regime after Suryo & Basaran (2006). Indeed, when inertial effects in both liquid streams are negligible, the inner to outer flow-rate and viscosity ratios are small enough and the capillary number is above an experimentally determined threshold which is predicted by our theoretical results with small relative errors, a steady micron-sized jet is issued from the apex of a conical drop. Under these conditions, the jet disintegrates into drops with a very well defined mean diameter, giving rise to a monodisperse microemulsion. Here, we demonstrate that the regime in which uniformly-sized drops are produced corresponds to values of the capillary number for which the cone-jet system is globally stable. Interestingly enough, our general stability theory reveals that liquid jets with a cone-jet structure are much more stable than their cylindrical counterparts thanks, mostly, to a capillary stabilization mechanism described here for the first time. Our findings also limit the validity of the type of stability analysis based on the common parallel flow assumption to only those situations in which the liquid jet diameter is almost constant.

show abstract

Section: Discussionmentioning

confidence: 99%

Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

2013

View full text Add to dashboard Cite

show abstract

“…The 50 , to differentiate the phenomena of charge relaxation and charge separation [50][51][52] . Due to the similar magnitudes of the electrical and hydrodynamic time scales (t e /t d ¼ (4D H þ )/(zm e,H þ )E1.35), the time scales can be approximated as t e Et d ¼ e i /K, where e i is the permittivity of liquid water and K is the combined ionic (or electrical) conductivity of pure water 51 .…”

Section: Discussionmentioning

confidence: 99%

Electrostatic charging of jumping droplets

et al. 2013

View full text Add to dashboard Cite

With the broad interest in and development of superhydrophobic surfaces for self-cleaning, condensation heat transfer enhancement and anti-icing applications, more detailed insights on droplet interactions on these surfaces have emerged. Specifically, when two droplets coalesce, they can spontaneously jump away from a superhydrophobic surface due to the release of excess surface energy. Here we show that jumping droplets gain a net positive charge that causes them to repel each other mid-flight. We used electric fields to quantify the charge on the droplets and identified the mechanism for the charge accumulation, which is associated with the formation of the electric double layer at the droplet-surface interface. The observation of droplet charge accumulation provides insight into jumping droplet physics as well as processes involving charged liquid droplets. Furthermore, this work is a starting point for more advanced approaches for enhancing jumping droplet surface performance by using external electric fields to control droplet jumping.

show abstract

“…The flow draws from the rim a thin sheet which destabilizes and sheds fluid cylinders. This streaming phenomenon provides a new route for generating monodisperse microemulsions.A highly conducting drop in a uniform electric field elongates into a prolate ellipsoid whose poles in strong fields deform into conical tips (Taylor cones) emitting jets of charged tiny droplets [1][2][3][4][5]. This so called electrohydrodynamic (EHD) streaming or cone-jetting occurs in many natural phenomena (e.g., drops in thunderclouds) and technological applications (printing, electrospraying, electrospinning) [4,6].…”

mentioning

confidence: 99%

Streaming from the Equator of a Drop in an External Electric Field

Brosseau

Vlahovska

2017

Phys. Rev. Lett.

View full text Add to dashboard Cite

Tip-streaming generates micron-and submicron-sized droplets when a thin thread pulled from the pointy end of a drop disintegrates. Here, we report streaming from the equator of a drop placed in a uniform electric field. The instability generates concentric fluid rings encircling the drop, which break up to form an array of microdroplets in the equatorial plane. We show that the streaming results from an interfacial instability at the stagnation line of the electrohydrodynamic flow, which creates a sharp rim. The flow draws from the rim a thin sheet which destabilizes and sheds fluid cylinders. This streaming phenomenon provides a new route for generating monodisperse microemulsions.A highly conducting drop in a uniform electric field elongates into a prolate ellipsoid whose poles in strong fields deform into conical tips (Taylor cones) emitting jets of charged tiny droplets [1][2][3][4][5]. This so called electrohydrodynamic (EHD) streaming or cone-jetting occurs in many natural phenomena (e.g., drops in thunderclouds) and technological applications (printing, electrospraying, electrospinning) [4,6].The streaming is related to a generic interfacial instability due to a convergent flow [7], see Figure 1.a. The interface is compressed and a local perturbation at the stagnation point (e.g., drop tips) gets drawn by the flow. If the viscous stresses overcome the interfacial tension, the perturbation grows into a fluid filament. This is the tip-streaming phenomenon commonly observed in the microfluidic co-flow geometry [8][9][10]. If instead of a point, the flow is converging to a stagnation line, then a thin sheet can be entrained [11]. By analogy with the cone-jet geometry resulting from the destabilization of a stagnation point, it is expected that the instability of a stagnation line would give rise to an edge-sheet structure. In this Letter, we report for the first time streaming resulting from a stagnation line instability.Experimentally, we exploit the electrohydrodynamic flow about a neutral drop placed in a uniform electric field [12,13]. By varying the fluid conductivities, we are able create flow converging either at the drop poles (Figure 1.b) to generate cone-jet, or at the equator ( Figure 1.c) to generate an edge-sheet. The latter case is the focus of this work. The electrohydrodynamic flow is driven by electric shear stresses due to induced surface charges [12,13]. For a drop in a uniform electric field the resulting flow is axisymmetrically aligned with the applied field. For a spherical drop with radius a placed in DC electric field E = Eẑ, the surface velocity is [12]where λ = µ in /µ ex is the viscosity ratio between the drop and suspending fluids and θ is the angle with the applied field direction. The direction of the surface flow depends on the difference of conductivity, σ, and permittivity, ε, of the drop and suspending fluids R = σ in /σ ex and S = ε in /ε ex . For highly conducting drops, R/S > 1, the surface flow is from the equator to the poles. Accordingly, the poles become stagnation p...

show abstract

Universal scaling laws for the disintegration of electrified drops

Cited by 167 publications

References 45 publications

Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

Global stability of stretched jets: conditions for the generation of monodisperse micro-emulsions using coflows

Electrostatic charging of jumping droplets

Streaming from the Equator of a Drop in an External Electric Field

Contact Info

Product

Resources

About