Flow characteristics around a plate withdrawn from a bath of yield stress fluid

Maillard, Mathilde; Boujlel, Jalila; Coussot, Philippe

doi:10.1016/j.jnnfm.2014.08.001

Cited by 22 publications

(34 citation statements)

References 33 publications

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“…These results highlight that the deposition of YSF on the wall of the channel is governed by Bi −1 . On the one hand, for Bi −1 > 1, the YSF is fluidized and the thickness of the deposited film increases with the velocity as observed recently in different geometries 26,33,36,37,46 . This efficient deposition process induces the rapid thinning of the plugs separating adjacent bubbles leading to their collapse.…”

Section: Bubble Production In Ysfsupporting

confidence: 61%

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

et al. 2016

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International audienceWe investigate experimentally the stability of bubble production in yield-stress fluids (YSF) and highly viscous silicone oil, using flow-focusing and T-junction devices. When the exit channel is initially pre-filled with the fluid and the gas is pressure-driven, the production is highly unstable, despite a regular frequency of bubble production in the junction. As observed for pressure-driven bubble trains in Newtonian fluids, we report that two mechanisms can explain these observations : (i) drastic reduction of the hydrodynamic pressure drop along the channel during the transient bubble production, which induces a rapid increase of the gas flow rate and (ii) thin film deposition resulting in a cascade of plug break-up and bubbles coalescence. While the drastic reduction of the pressure drop is inevitable in such two-phase flows, we show that modifying the surfaces of the channel can help stabilizing the system when the continuous phase is a YSF. To do so, we measure the thickness of the film deposited on the channel wall for rough and smooth channels. Our results are rationalized by introducing the inverse of the Bingham number Bi −1 comparing the viscous stress to the yield stress. For Bi −1 ≥ 1, a fast fluidization process associated to efficient deposition of YSF on the channel wall leads to a rapid destabilization of the bubble production. However, for Bi −1 < 1, the deposition driven by capillarity can be hindered by the wall-slip induced by the existence of the yield stress: the thickness of the deposited film is very thin and corresponds to the equivalent roughness of the channels. It is typically 40 µm thick for rough surfaces and below the limit of resolution of our setup for smooth surfaces. In this regime of Bi −1 and for smooth surfaces, the length of the plugs barely vanishes, thus the start-up flow is less prone to destabilization. These results therefore potentially open routes to steady production of aerated YSF on smooth channels in the regime of small Bi −1

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Section: Bubble Production In Ysfsupporting

confidence: 61%

On the stability of the production of bubbles in yield-stress fluid using flow-focusing and T-junction devices

et al. 2016

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“…The flow visualization has been attempted qualitatively either by addition of particles or small bubbles [40,48] and also by injection of a dye [49]. The quantitative velocity field in the liquid can be inspected by Particle Image velocimetry (PIV) [30,31]. The liquid is seeded with micron-size particles illuminated by a laser sheet [47] and images are recorded with a high speed camera.…”

Section: Experimental Techniquesmentioning

confidence: 99%

“…As we mentioned in Sec. 4.3, Maillard et al controlled the interfacial condition of Carbopol solutions, a yield stress fluid, by using a rough substrate to prevent slippage [30,31]. This slippage is due to a layer of solvent between the polymers present in the bulk of the solution and the surface of the solid.…”

Section: Rough and Textured Surfacesmentioning

confidence: 99%

Withdrawing a solid from a bath: How much liquid is coated?

Rio

Boulogne

2017

Advances in Colloid and Interface Science

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A solid withdrawn from a liquid bath entrains a film. In this review, after recalling the predictions and results for pure Newtonian liquids coated on simple solids, we analyze the deviations to this ideal case exploring successively three potential sources of complexity: the liquid-air interface, the bulk rheological properties of the liquid and the mechanical or chemical properties of the solid. For these different complexities, we show that significant effects on the film thickness are observed experimentally and we summarize the theoretical analysis presented in the literature, which attempt to rationalize these measurements.

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“…We now solve (13)- (14) subject to h → 1 on the right and h → 1 2 κξ 2 on the left, with κ determined by (15) which assures that the solution for the film at the back of the bubble corresponds to that matching the front meniscus. As illustrated by the numerical solution for B = 1 shown in figure 2(a), the solution accomplishes the decay to h = 1 by passing through an infinite sequence of switches in the sign of h − 1.…”

Section: At the Back Of The Bubblementioning

confidence: 99%

“…The existing computations deal with relatively large Capillary number, outside of the regime of validity of Bretherton's lubrication-style theory, and so there is minimal overlap between our results and these previous studies. Also relevant are experiments on the viscoplastic Landau-Levich problem [14,15] and the work of [16] on the steady motion of viscoplastic plugs down conduits representing idealized airways. A variety of other interfacial flow problems involving bubbles in viscoplastic fluids, of indirect relevance to the present work, are reviewed by [17].…”

Section: Introductionmentioning

confidence: 99%