Natural thermal convection in fractured porous media

Cécile Mezon (1, 2) , Valeri V. Mourzenko (3, 4, 5) , Jean-François Thovert (4, 3, 5) , Raphaël Antoine (6) , Anthony Finizola (1) , P.M Adler (2)

1 LGSR - Laboratoire GéoSciences Réunion
2 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols
3 Département FTC - Département Fluides, Thermique et Combustion [Institut Pprime]
4 CH - Combustion hétérogène et milieu poreux [Institut Pprime]
5 PPrime [Poitiers] - Institut Pprime [UPR 3346]
6 ENDSUM - Evaluation non destructive des structures et des matériaux

In the crust, fractures/faults can provide preferential pathways for fluid flow or act as barriers preventing the flow across these structures. In hydrothermal systems (usually found in fractured rock masses), these discontinuities may play a critical role at various scales, controlling fluid flows and heat transfer. The thermal convection is numerically computed in 3D fluid satured fractured porous media. Fractures are inserted as discrete objects, randomly distributed over a damaged volume, which is a fraction of the total volume. The fluid is assumed to satisfy Darcy's law in the fractures and in the porous medium with exchanges between them. All simulations were made for Rayleigh numbers (Ra) < 150 (hence, the fluid is in thermal equilibrium with the medium), cubic boxes and closed-top conditions. Checks were performed on an unfractured porous medium and the convection cells do start for the theoretical value of Ra, namely 4p². 2D convection was verified up to Ra=800. The influence of parameters such as fracture aperture (or fracture transmissivity), fracture density and fracture length is studied. Moreover, these models are compared to porous media with the same macroscopic permeability. Preliminary results show that the non-uniqueness associated with initial conditions which makes possible either 2D or 3D convection in porous media (Schubert & Straus 1979) is no longer true for fractured porous media (at least for 50

Domaines: Milieux fluides et réactifs; Mécanique des fluides [physics.class-ph]

Cécile Mezon, Valeri V. Mourzenko, Jean-François Thovert, Raphaël Antoine, Anthony Finizola, et al.. Natural thermal convection in fractured porous media. 2015 AGU Fall Meeting, Dec 2015, San Francisco, California, United States. ⟨hal-03110180⟩