On the effect of surfactants on drop coalescence at liquid/liquid interfaces

Weheliye, Weheliye Hashi; Dong, Teng; Angeli, Panagiota

doi:10.1016/j.ces.2016.12.009

Cited by 43 publications

(26 citation statements)

References 19 publications

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“…The increase of the surfactant concentration also shifts the rupture points off-axis. 29 For ϕ = 0, the rupture points are close to the center axis of the drop and the average horizontal distance between the rupture point and the central axis over 15 coalescence events is (0.24 ± 0.06)D. This distance increases to (0.36 ± 0.03)D for ϕ = 1.3 × 10 6 . At the low surfactant concentration at t = 0.44t σ , the oil film takes longer to retract outwards on the right-hand side of the rupture point, while on the left-hand side, the film drainage has already finished.…”

Section: Evolution Of the Drop Surface During Coalescencementioning

confidence: 80%

“…The drop surface approaches the final flat interface position for total coalescence, which is similar to previous observations by Mohamed-Kassim and Longmire 20 and Weheliye, Dong, and Angeli. 29 …”

Section: Evolution Of the Drop Surface During Coalescencementioning

confidence: 99%

“…When the surfactant concentration increases to ϕ = 1.3 × 10 4 , total coalescence is observed and the evolution of the vortices was discussed in a previous study by Weheliye, Dong, and Angeli. 29 …”

Section: E Vorticity Fields Inside the Droplet During Coalescencementioning

confidence: 99%

“…To check the repeatability of the PIV results, the average circulation level, 29 tests, was plotted for ϕ = 0 and ϕ = 1.3 × 10 6 . The circulation, Γ ω , was estimated from Eq.…”

Section: B Setup For Piv Measurementsmentioning

confidence: 99%

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An experimental study on the drop/interface partial coalescence with surfactants

et al. 2017

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This paper presents investigations on the partial coalescence of an aqueous drop with an organicaqueous interface with and without surfactants. The organic phase was different silicone oils and the aqueous phase was a glycerol-water solution at different concentrations. It is found that when the surfactant Span 80 is introduced into the organic phase, the partial coalescence region is reduced in the Oh-Bo coalescence map. The range of the inertio-capillary regime reduces when surfactants are present, while the drop size ratio decreases with increasing surfactant concentration. The velocity fields inside the aqueous drop were studied with high speed particle image velocimetry for the first time. In the surfactant-free system, it was found that the inward motion of the fluids at the upper part of the drop favours the generation of a liquid cylinder at the early stages of coalescence. The pressure gradient created by the downward stream at the bottom of the liquid cylinder drives the pinch-off of the secondary drop. When surfactants are present, the rupture of the film between the drop and the interface occurs at an off-axis location. The liquid cylinder formed in this case is not symmetric and does not lead to pinch-off. It is also found that the vortices inside

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Section: Evolution Of the Drop Surface During Coalescencementioning

confidence: 80%

Section: Evolution Of the Drop Surface During Coalescencementioning

confidence: 99%

Section: E Vorticity Fields Inside the Droplet During Coalescencementioning

confidence: 99%

“…To check the repeatability of the PIV results, the average circulation level, 29 tests, was plotted for ϕ = 0 and ϕ = 1.3 × 10 6 . The circulation, Γ ω , was estimated from Eq.…”

Section: B Setup For Piv Measurementsmentioning

confidence: 99%

See 2 more Smart Citations

An experimental study on the drop/interface partial coalescence with surfactants

et al. 2017

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“…Gravity and Laplace pressure cause a strong downward motion of the aqueous phase from the drop to the bulk continuous phase (Weheliye et al 2017) would have an effect on the film drainage rate and the local flow fields, as discussed by Bordoloi and Longmire (2012) on the effect of neighbouring particles on drop coalescence. Chinaud et al (2016) showed that two more counteracting vortices form in the bulk coalescing phase.…”

Section: Coalescence Dynamicsmentioning

confidence: 99%