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Capillary threads and viscous droplets in square microchannels
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10.1063/1.2911716
/content/aip/journal/pof2/20/5/10.1063/1.2911716
http://aip.metastore.ingenta.com/content/aip/journal/pof2/20/5/10.1063/1.2911716

Figures

Image of FIG. 1.
FIG. 1.

Typical capillary number-based flow map with flow patterns: (a) threading (●), (b) jetting (▶), (c) dripping (◼), (d) tubing (◆), (e) viscous displacement (+). fluid pair: .

Image of FIG. 2.
FIG. 2.

Stable capillary thread diameter vs flow rate ratio . Inset: experimental micrograph with arrow showing contact line between and and glass wall. Fluid pairs: (●), (◼), (⊠), (○), (◻), and (▷).

Image of FIG. 3.
FIG. 3.

Jetting regime. Thread breakup location occurs near fluid junction and is adjusted with flow rates in : (a) , ; (b) , ; (c) , ; (d) , (fluid pair: ).

Image of FIG. 4.
FIG. 4.

Normalized jetting droplet diameter vs the flow rate ratio . Solid line: . Inset: ratio vs . Solid line: . Fluid pairs: (◆), (⊠), (◻) (◇), (▷), (△).

Image of FIG. 5.
FIG. 5.

Experimental critical thread length before jetting droplets compared to the prediction of Eq. (3) (solid line). Fluid pairs: (◆), (▲), (⊗), (⊠), (◻), (◇), and (△).

Image of FIG. 6.
FIG. 6.

Examples of microchannel confinement of varicose deformations (flow rates in ): (a) Bead-on-a-string structure: , ; (b) , ; (c) , .

Image of FIG. 7.
FIG. 7.

Dynamics of dripping: (a) Time series of a cycle of viscous droplet formation: (i)–(ii) cap displacement, (ii)–(iii) cap squeezing, (iii)–(iv) pinching, (v) tail stretching, and (vi)–(vii) complete breakup. (b) Time-space diagram of (a) with corresponding events taken along the centerline of the channel. (c) Front velocity of a small droplet, , during breakup (flow rates in ): , (fluids pair: ). (d) Front velocity of a large droplet, , during breakup: , (fluids pair: ). The arrow indicates the end of the pinching stage.

Image of FIG. 8.
FIG. 8.

Normalized droplet length vs . Line (i): , line (ii): . Fluids pairs: (●), (◆), (▲), (▶), (⊗), (⊠), (○), (○), (◇), (▷), and (△). Inset: effect of for fixed volume fraction: (flow rates in ) (a) , ; (b) , ; (c) (fluid pair: G3E).

Image of FIG. 9.
FIG. 9.

Critical tail length at breakup, , of a viscous droplet vs Eq. (5). Fluids: (●), (◆), (▲), (▶), (⊗), (⊠), (⊠), (▷), and (△). Inset: Example of cometlike droplets with long tails (flow rates in ): [(a) and (b)] , ; (c) (fluids pair: ).

Image of FIG. 10.
FIG. 10.

Examples of flow regimes limiting the steady formation of threads and droplets: (a) Hysteresis between tubing and threading regimes (flow rates in ): (i) , and , (ii) , and (fluid pair: ). (b) Viscous displacement regime (finger of at counterflow with ): (i) , , (ii) , , (iii) , , (iv) and, . (c) Typical wetting behaviors: (i) sticking droplet, , ; stratification: (ii), , (iii) , .

Tables

Generic image for table
Table I.

Physicochemical properties of pairs of liquids ( and ): and are corresponding viscosities, is the viscosity ratio, and is the interfacial tension. For marked by (∗), the volume percentage of glycerol in the mixture is given. All properties are measured at room temperature.

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/content/aip/journal/pof2/20/5/10.1063/1.2911716
2008-05-01
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Capillary threads and viscous droplets in square microchannels
http://aip.metastore.ingenta.com/content/aip/journal/pof2/20/5/10.1063/1.2911716
10.1063/1.2911716
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