Bubble size and air content of wet fibre foams in axial mixing with macro-instabilities

Al-Qararah, Ahmad M.; Hjelt, Tuomo; Koponen, Antti; Harlin, Ali; Ketoja, Jukka A.

doi:10.1016/j.colsurfa.2013.08.051

Cited by 42 publications

(29 citation statements)

References 30 publications

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“…All foams were generated with a combination of tank mixing and inline generation in a short flow loop, see Figure 1. The tank mixer has been specifically designed for foam generation and it has two round impeller plates with opposite edges slighty bended up and down [16]. The inline generation was implemented by injecting compressed air into the SDS solution in a specifically designed inline generation block where the flow field is highly turbulent.…”

Section: Figure 1 a Schematic View Of The Foam Generation System Fomentioning

confidence: 99%

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Experimental results on the flow rheology of fiber-laden aqueous foams

Jäsberg

Selenius

Koponen

2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Section: Figure 1 a Schematic View Of The Foam Generation System Fomentioning

confidence: 99%

“…After a long silent period, foam-coating [13,14] and foam-forming are now attracting increasing interest in paper industry [15][16][17][18][19][20]. The use of foam allows the inclusion of a wide variety of alternative raw materials, such as nanoparticles [21], nanocellulose [22] and long flexible fibers.…”

Section: Introductionmentioning

confidence: 99%

Experimental results on the flow rheology of fiber-laden aqueous foams

Jäsberg

Selenius

Koponen

2015

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…In the papermaking framework, several experimental studies (Al-Qararah et al, 2013, 2015bJäsberg et al, 2015;Haffner et al, 2017) have recently investigated the influence of the fibres (depending on their physico-chemical characteristics) on the properties of the wet foam used as carrier fluid: incor-15 porating fibres while mixing the foaming liquid produces a foam with smaller bubbles and a higher liquid fraction than without fibres. Foam viscosity has been found to increase with increased content of rough wood fibres, although the foam still remains shear-thinning.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of a flexible fibre in a sheared two-dimensional foam: Numerical simulations

Langlois

Hutzler

2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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Recently there has been a renewed interest in using foamy suspensions of wood fibres as a carrier fluid in papermaking but there is a lack of fundamental understanding of the dynamics of such a three-phase system. In this article we propose a numerical model for the dynamics of an individual flexible fibre within a flowing foam, based on discrete-element methods. As is observed in a Newtonian shear flow, we observe that the fibre systematically experiences a tumbling instability: the disordered motion of bubbles cannot prevent the pseudo-periodical flip of the fibre. Our simulations show that the tumbling time decreases almost as the inverse of the strain rate. It also decays when the fibre length is increased, though for long enough fibres it reaches a constant value. Similarly the tumbling time is also surprisingly independent of the stiffness of the fibre. Because of their tumbling motion, long and flexible fibres spend most of the time in a coiled geometry. This would imply that using foam as a carrier fluid is not enough to keep fibres aligned with the flow. However, further refinements of the model will need to be considered to arrive at firm conclusions regarding alignment. Dear Editor,We would like to thank the referee for his careful reading and constructive remarks. We tried to follow his recommendations, and to answer his comments and concerns regarding the article. The modifications we brought to the paper are listed below:Reviewer #1 * General questions that seem not to be addressed are: Is there shear-banding or localisation? Does it matter where between the side walls the fibre is placed? (I guess it shouldn't, but I presume that this was checked.)Since no additional wall friction is added (see our previous study of the bubble model in Langlois et al. [2008]), no shear-banding is observed. The average velocity profile is mostly undisturbed by the presence of a unique fibre, and remains linear.The initial y-position of the fibre is of no influence, except in the 'pathological' case where it comes in contact with one of the walls and remains there.* lines 10-20 are not very clear on how the presence of the fibres affects these foam properties; it would be useful to expand this section to give the reader more of a feel for the complexity of this area of research and the way in which a foam interacts with fibres.We have added to the introduction a more thorough description on the effects of fibres on the foam, recently observed experimentally (l.15 to 21).* lines 63 and 96: I find the use of the word "spherical" misleading, since in a 2D experiment bubbles are more discoidal than spherical and they are certainly treated here as discs. Once the description of the bubble model is restricted to 2D, I suggest to use "discs" exclusively.In the simulations the bubbles are indeed treated as disks, though we had initially used the term "spheres" since these disks are meant to mimick a bubble raft made of roughly spherical bubbles seen from above. However we agree that this can lead to some confusion...

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“…Although the technique has been known since 1974 [1] it has been only very recently that the interactions between fibres and foam have been examined in greater detail. [2,3,4,5,6].…”

Section: Introductionmentioning

confidence: 99%

“…drainage rate, bubble size distribution, coarsening rate) significantly. Recent work [2,3,4] concerned mainly wet foams, i.e. those with liquid volume fraction φ 0.2, and focused on the effect of the presence of fibres on global properties such as stability of the foam [5] or rheology [7] of fibre suspensions.…”

Section: Introductionmentioning

confidence: 99%

Interactions of fibres with simple arrangements of soap films

Whyte

Haffner

Tanaka

et al. 2017

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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We present experiments and Surface Evolver simulations concerning the interaction of fibres with simple arrangements of soap films, which constitute model systems for dry foams. For a fibre inserted into a soap film which spans two Plateau borders, our simulation accurately predicts the variation in the length of the film as the fibre thickness is varied. For a fibre introduced into a Plateau border, simulations accurately predict the variation in length of the Plateau border as the fibre diameter is varied, and as it is moved. We suggest that the force necessary to move the fibre from equilibrium may act to inhibit foam coarsening, in line with observations from experiments on fibreladen foams. EUFOAM Proceedings OfficeDublin, 28/10/2016 Dear Editor, Please find enclosed our manuscript entitled: "Interactions of fibres with simple arrangements of soap films" which was presented in the last EUFOAM Conference by David Whyte. This work presents an experimental investigation of the configuration of soap films in the presence of fibre. The data are described both theoretically and numerically. The very good description of our experimental data with our simulations allow to predict the configuration of the films as a function of the features of the fibre.In addition, our observations raise the question of the interaction between foam and fibres at the macroscopic scale, this appears as a promising topic, in particular for industry dealing with novel materials. Thus, we believe our observations should interest the broad community of researcher in fluid mechanics working on foam containing solid material. We therefore would be very excited to see this work published in the EUFOAM Proceedings, which we believe reaches the most relevant audience for our work. AbstractWe present experiments and Surface Evolver simulations concerning the interaction of fibres with simple arrangements of soap films, which constitute model systems for dry foams. For a fibre inserted into a soap film which spans two Plateau borders, our simulation accurately predicts the variation in the length of the film as the fibre thickness is varied. For a fibre introduced into a Plateau border, simulations accurately predict the variation in length of the Plateau border as the fibre diameter is varied, and as it is moved. We suggest that the force necessary to move the fibre from its equilibrium position may act to inhibit foam coarsening, in line with previous observations from experiments on fibre-laden foams.

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Bubble size and air content of wet fibre foams in axial mixing with macro-instabilities

Cited by 42 publications

References 30 publications

Experimental results on the flow rheology of fiber-laden aqueous foams

Experimental results on the flow rheology of fiber-laden aqueous foams

Dynamics of a flexible fibre in a sheared two-dimensional foam: Numerical simulations

Interactions of fibres with simple arrangements of soap films

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