{"id":16415,"date":"2024-07-22T18:57:49","date_gmt":"2024-07-22T16:57:49","guid":{"rendered":"https:\/\/navier-lab.fr\/?page_id=16415"},"modified":"2024-09-06T10:37:48","modified_gmt":"2024-09-06T08:37:48","slug":"bubbly-media-and-foams","status":"publish","type":"page","link":"https:\/\/navier-lab.fr\/en\/research\/rheophysics-porous-media\/bubbly-media-and-foams\/","title":{"rendered":"Bubbly Media and Foams"},"content":{"rendered":"

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Our research group has investigated liquid foams, interfaces and soap films for over a decade. We focus on the mechanical stability of thin liquid films, granular films and gas marbles<\/em>. We are also interested in the rheology, the coarsening and the stability of simple bubbly media or complex aerated materials, along with the production and the shaping of foamed coatings and foamed construction materials.<\/p>\n

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\n \"Coarsening\n <\/figure>
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Coarsening of liquid foams<\/h2>Read More<\/a><\/div>\n <\/article><\/div><\/div>
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Granular films and gas marbles<\/h2>Read More<\/a><\/div>\n <\/article><\/div><\/div>
\n \"Bubbly\n <\/figure>
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Stability of aerated yield-stress fluids<\/h2>Read More<\/a><\/div>\n <\/article><\/div><\/div>
\n \"Cement\n <\/figure>
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Foamed construction materials<\/h2>Read More<\/a><\/div>\n <\/article><\/div><\/div><\/div><\/div><\/section>
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Coarsening of liquid foams<\/h3>\n

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O. Pitois, N. Galvani (PhD)<\/h5>\n
Collaborations : S. Cohen-Addad, R. H\u00f6hler (INSP), D. Langevin, E. Rio, A. Salonen (LPS), D. J. Durian (U. Pennsylvania), S. Vincent-Bonnieu (ESA)<\/h5>\n

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\nIn liquid foams, we name coarsening<\/em> the gas diffusion from one bubble to another through the liquid that separates them. Coarsening leads to a decrease in the number of bubbles and to an increase of their average size. While many applications deal with wet<\/em> foams, i.e. with a liquid volume fraction above 20%, these foams have been seldom studied because of their instability to liquid drainage due to gravity.<\/p>\n

We have joined a European consortium led by Dominique Langevin in the framework of a MAP Contract (Hydrodynamics of Wet Foams) with the European Space Agency to study liquid foam coarsening on the International Space Station <\/em>(!). The first round of experiments conducted in 2020 have yielded precious results related to the bubble growth dynamics for a broad range of liquid volume fractions from wet foams to bubbly liquids (50 %). We have observed a change in the coarsening regime from a growth with t<\/em>1\/2<\/sup> for small liquid fractions to t<\/em>1\/3<\/sup> for the larger liquid fractions. One of our main results is that the volume fraction for which the change of regime occurs (0.39) is laregly above the Random Close Packing volume fraction (0.31 as the foams are not monodisperse). We have shown that this deviation is caused by small adhesion forces that keep the average contact area between bubbles to a non-zero value beyond Random Close Packing. We have also highlighted an excess of small bubbles (named roaming bubbles<\/em>) in the bubble size distribution compared to theoretical models. We have shown that these bubbles have lost contact with the foam bubbles, which impedes their dissolution. These roaming bubbles<\/em> had never been seen before.<\/p>\n

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Credits : ENPC, Ingenius
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References<\/h4>\n