Rising bubbles in yield stress materials

Lopez, William F.; Naccache, Mônica F.; Mendes, Paulo R. de Souza

doi:10.1122/1.4995348

Cited by 44 publications

(67 citation statements)

References 31 publications

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“…As the bubble grows, inertia forces grow and exceed the surface tension, which becomes negligible. These results are in contrast with the ones observed in the experimental study made by Sikorski et al (2009) and Lopez et al (2017), where it was observed bubble shapes with a rounded head and a cusped tail. How-ever, this difference can be due to elasticity that is present in the fluid used in the experiments.…”

Section: Fig 6 Wall Effect On Bubble Velocity For τY =contrasting

confidence: 99%

“…5, where it is noted that the Reynolds number decreases with the Bingham number up to a certain value of Bn above which the force balance be-tween yield stress and buoyancy leads the bubble to remain stagnant. These results are in qualitative agreement with the ones obtained in Dimakopoulos et al (2013) and Lopez et al (2017). Fig.…”

Section: Single Bubblesupporting

confidence: 92%

“…These works show that bubble shape and displacement are a result of the contribution of buoyancy, viscous forces, inertia and surfacetension. The presence of shear thinning, yield stress and elasticity play also an important role (Dubash and Frigaard (2004); Dubash and Frigaard (2007); Zhang et al (2010); Fraggedakis et al (2016); Funfschilling and Li (2001); Sikorski et al (2009); Lopez et al (2017); Lind and Phillips (2010); Premlata et al (2017); Amirnia et al (2013); Smolianski et al (2008); Tripathi et al (2015); Tsamopoulos et al (2008); Xu et al(2017)). Despite all these and other relevant works, the displacement phenomena is not completely understood.…”

Section: Introductionmentioning

confidence: 99%

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Air Bubbles Displacement in Yield Stress Fluids

Naccache

Abdu

Abreu

2020

JAFM

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The motion of air bubbles in a yield stress fluid is analyzed numerically using a 2D approach and the finite volume technique. The multiphase flow is simulated using the volume of fluid method (VoF), which solves the conservation equations of mass and momentum coupled to a transport equation for the volume fraction of the fluids. The effects of yield stress, bubble size, number and position of bubbles rising in a viscoplastic fluid confined between vertical parallel plates are analyzed and discussed. The results indicate that the yield stress has great impact on the rising velocity. In the case of multiple bubbles flowing vertically, it is observed that the displacement of one bubble influences the rising velocity of the others, causing them to approach each other. As the distance between the bubbles increases the interference is reduced and the bubbles begin to flow as single ones. When two bubbles are horizontally positioned, they can approach or move away from each other, depending on the initial distance between them. Furthermore, the bubbles shape is analyzed as a function of the governing parameters. It is observed that for lower Reynolds number the bubbles present a circular shape, but as inertia increases the bubble becomes ellipsoidal.

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Section: Fig 6 Wall Effect On Bubble Velocity For τY =contrasting

confidence: 99%

Section: Single Bubblesupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

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Air Bubbles Displacement in Yield Stress Fluids

Naccache

Abdu

Abreu

2020

JAFM

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“…pastes, slurries, emulsions and microgels which possess a characteristic stress τ y below which they stop flowing and behave as solids [1,2]. They may trap bubbles when buoyancy-induced stresses do not suffice to yield the material [3][4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Oscillations of small bubbles and medium yielding in elastoviscoplastic fluids

et al. 2019

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We investigate the radial oscillations of small gas bubbles trapped in yield-stress fluids and driven by an acoustic pressure field. We model the rheological behavior of the yield-stress fluid using the recently developed elasto-visco-plastic (EVP) constitutive equation that takes into account the elastic and visco-plastic deformations of the material [P. Saramito, J. NonNewton. Fluid Mech.158 (1-3) (2009) pp. 154161]. Assuming that the bubble remains spherical during the pressure driving, we reduce the problem to a set of ODEs and an integrodifferential equation, which we solve numerically for the case of two yield stress fluids, a soft Carbopol gel and a stiffer Kaolin suspension.We find that, depending on the amplitude and frequency of the pressure field, the radial oscillations of the bubble produce elastic stresses that may or may not suffice to yield the surrounding material.We evaluate the critical amplitude of the acoustic pressure required to achieve yielding and we find a good agreement between numerical simulations and an analytical formula derived under the assumption of linear deformations. Finally, we examine the bubble oscillation amplitude for a very wide range of applied pressures both below and above the critical value to assess the impact of yielding on the bubble dynamics. This analysis could be used to identify a signature of yielding in experiments where the radial dynamics of a bubble is measured. More generally, these results can be used to rationalize the optimal conditions for pressure-induced bubble release from yield-stress fluids, which is relevant to various biomedical and industrial applications, including oil industry and food processing.

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“…Elastic effects can be observed also in the fluid phase. For example, bubbles rising in Carbopol solutions usually acquire the shape of an inverted teardrop, with a cusp at their leeward side [13,14], but the classical Bingham and HB viscoplastic models fail to predict such behaviour [15,16]; on the other hand, such shapes are observed also in viscoelastic fluids, and are correctly captured by viscoelastic constitutive equations [17]. Similarly, for the settling of spherical particles in Carbopol, classical VP models cannot predict phenomena such as the loss of fore-aft symmetry under creeping flow conditions and the formation of a negative wake behind the sphere, but these phenomena are predicted if elasticity is incorporated into the constitutive modelling [18].…”

Section: Introductionmentioning

confidence: 99%

A finite volume method for the simulation of elastoviscoplastic flows and its application to the lid-driven cavity case

Syrakos

Dimakopoulos

Tsamopoulos

2020

Journal of Non-Newtonian Fluid Mechanics

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We propose a Finite Volume Method for the simulation of elastoviscoplastic flows, modelled after the extension to the Herschel-Bulkley model by Saramito [J. Non-Newton. Fluid Mech. 158 (2009) 154-161]. The method is akin to methods for viscoelastic flows. It is applicable to cell-centred grids, both structured and unstructured, and includes a novel pressure stabilisation technique of the "momentum interpolation" type. Stabilisation of the velocity and stresses is achieved through a "both sides diffusion" technique and the CUBISTA convection scheme, respectively. A second-order accurate temporal discretisation scheme with adaptive time step is employed. The method is used to obtain benchmark results of lid-driven cavity flow, with the model parameters chosen so as to represent Carbopol. The results are compared against those obtained with the classic Herschel-Bulkley model. Simulations are performed for various lid velocities, with slip and no-slip boundary conditions, and with different initial conditions for stress. Furthermore, we investigate the cessation of the flow, once the lid is suddenly halted.

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Rising bubbles in yield stress materials

Cited by 44 publications

References 31 publications

Air Bubbles Displacement in Yield Stress Fluids

Air Bubbles Displacement in Yield Stress Fluids

Oscillations of small bubbles and medium yielding in elastoviscoplastic fluids

A finite volume method for the simulation of elastoviscoplastic flows and its application to the lid-driven cavity case

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