BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Simon Cox (Aberystwyth University) DTSTART:20260526T120000Z DTEND:20260526T130000Z DTSTAMP:20260423T022229Z UID:UEA_mth/27 DESCRIPTION:Title: Bubble properties and growth rates in coarsening wet foams\nby Simon Cox (Aberystwyth University) as part of Fluids and Structures Seminar @ UE A\n\nLecture held in SCI 3.05.\n\nAbstract\nIn an aqueous foam\, gas can d iffuse through the liquid phase\, changing the sizes of the bubbles. On\na verage\, large bubbles grow while small bubbles shrink\, and subsequently disappear. Thus the average\nbubble size increases\, and the length-scale of the foam coarsens. This reduces the efficacy of foams in\napplications such as soil remediation and firefighting\, and it reduces the shelf-life of foamed foods.\n\nCoarsening is well characterised in the low (dry foam) and high (dilute) limits of liquid fraction ϕ. In\nthe dry limit (ϕ =0) the gas flow is through the thin films separating polyhedral bubbles\, wh ile in the\ndilute limit (ϕ =100%) there are no thin films and the gas fl ows through bulk liquid between isolated\nspherical bubbles. Growth laws f or individual bubbles are known\, as is the exponent of time by which\nthe average bubble size evolves in a scaling state. However\, these propertie s have not yet been\nconvincingly established for intermediate liquid frac tions\, which are found in most applications.\n\nThe growth rate of a bubb le is determined by (i) its pressure relative to that of its neighbours\, which is\nrelated to the curvature of its liquid/gas interfaces\, and (ii) its surface area in contact with other\nbubbles. I will describe mean-fie ld approximations for a bubble’s pressure and contact area at arbitrary\ nliquid fraction [1]\, validated against bubble-scale simulations.\n\nThes e approximations can be combined to give a growth law for a bubble of a gi ven size in a\ncoarsening foam of a given liquid fraction. From this growt h law we predict scaling-state bubble size\ndistributions\, that is\, we f ind a similarity solution of the continuity equation for the number of bub bles\nthat leaves the distribution of bubble sizes\, when scaled by their average\, independent of time. I will\npresent results for various liquid fractions [2] and compare them with recent experiments on the\nInternation al Space Station [3].\n\nReferences\n\n[1] J. Morgan and S.J. Cox (2024) E ffects of liquid fraction and contact angle on structure and coarsening in \ntwo-dimensional foams. J. Fluid. Mech.\, 999: A10.\n\n[2] J. Morgan and S.J. Cox (2026) Mean-field model of bubble size distribution in coarsening wet foams. Soft\nMatter\, 22: 1601-1617.\n\n[3] Galvani\, N.\, et al. (20 23). Hierarchical bubble size distributions in coarsening wet liquid foams . Proc. Nat.\nAcad. Sci\, 120: e2306551120.\n LOCATION:https://researchseminars.org/talk/UEA_mth/27/ END:VEVENT END:VCALENDAR