Morphologie of air invasion in an immersed granular layer

German Varas (1) , Valérie Vidal (1) , Jean-Christophe Géminard (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon

We report a study of the paths formed by a finite volume of air gently injected at the base of an immersed granular material. A two-dimensional model, based on experimental observations, shows that the typical height and width of the region explored by the branched path depend not only on the injected volume V but also on a dimensionless parameter χ which accounts for the relative effects of the gravity and capillarity: for a given injected volume V , larger gravity effects lead to taller and narrower structures; for a given χ, the typical height and width of the structure scale like V^1/2 and V^1/4, respectively while the typical gaseous fraction in the corresponding region increases accordingly like V^1/4. Such results could be of practical importance: for instance, gas can be trapped on purpose in an underground natural container below a granular slurry. Our results can help in predicting if the gas is likely to reach the free surface and escape the system if the container presents a defect (hole or fracture).

Domaines: Matière Molle [cond-mat.soft]

German Varas, Valérie Vidal, Jean-Christophe Géminard. Morphologie of air invasion in an immersed granular layer. Physical Review E : Statistical, Nonlinear, and Soft Matter Physics, 2011, 83 (6), pp.061302. ⟨10.1103/PhysRevE.83.061302⟩. ⟨hal-00596863⟩