InterPore2026

Foam confined in granular media: liquid distribution & consequences

19 May 2026, 14:20

15m

Oral Presentation (MS05) Physics of multiphase flow in diverse porous media MS05

Speaker

Vincent Langlois (Laboratoire Navier, Université Gustave Eiffel)

Description

Liquid foams are widely used in porous and granular media in applications such as enhanced oil recovery, soil remediation, and tunneling. In these contexts, foams are injected or generated within a solid matrix, where their structure and dynamics are strongly affected by confinement and by interactions with the grain surfaces.
In a series of recent works [1–4], we have investigated how the presence of a granular skeleton modifies the physical behavior of liquid foams. When a foam is introduced into a granular packing, the liquid phase no longer remains uniformly distributed within the foam structure (Fig. 1a). Instead, a significant fraction of the liquid is extracted from the foam confined within the pore space and redistributed to the surface of the grains. This liquid accumulates preferentially at grain–grain contacts, where capillary bridges are formed (Fig. 1b), and within a liquid-rich surface network associated with the contacts between the foam and the grain surfaces. This redistribution is driven by capillary pressure differences between the gas–liquid interfaces in the foam and the highly curved liquid interfaces at the grain scale. As a consequence, the foam core confined within the pore space becomes effectively drier than the same foam in bulk, due to the presence of substantial amounts of liquid stored in capillary bridges and surface-associated liquid networks at the solid boundaries.
We show that this liquid transfer provides a unifying framework to interpret several key properties of foams in granular media. First, we examine the flow of foam through porous packings and focus on the apparent yield stress. Compared to bulk foams, confined foams exhibit an enhanced resistance to flow, which can be quantitatively interpreted as the response of a bulk foam with a reduced effective liquid fraction (Fig. 1c). Second, we investigate the coarsening dynamics of bubbles within granular packings. Bubble growth by gas diffusion is found to be significantly enhanced under confinement. This increase in coarsening rate is consistent with the effective drying of the foam core, which leads to an increase in the total area of thin liquid films available for gas exchange (Fig. 1d).
Overall, our results suggest that many aspects of foam behavior in granular and porous media can be rationalized by mapping the confined foam onto an equivalent bulk foam characterized by an effective liquid fraction.

Figure 1 – (a) Liquid repartition between the foam filling the pore (ϕ_l^eff), the wall Plateau border of bubbles in contact with grains (ϕ_l^wall) and liquid bridges at the interface (ϕ_l^bridge). (b) The effective liquid fraction of the core foam decreases as the bubble/grain sizes (R_b/R_g) ratio increases [3]. This effective liquid fraction rationalizes the effect of the liquid fraction on (c) the apparent yield stress σ_y (normalized by a capillary pressure) and (d) the coarsening rate Ω of the confined foam. Full lines correspond to the relationship found for bulk foam.