Details

Autor(en) / Beteiligte

• Liang, Yu
• Wen, Baole
• Hesse, Marc A.
• DiCarlo, David

Titel

Effect of Dispersion on Solutal Convection in Porous Media

Ist Teil von

• Geophysical research letters, 2018-09, Vol.45 (18), p.9690-9698

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2018

Link zum Volltext

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Solutal convection in porous media is thought to be controlled by the molecular Rayleigh number, Ram, the ratio of the buoyant driving force over diffusive dissipation. The mass flux should increase linearly with Ram and the finger spacing should decrease as Ram−1/2. Instead, our experiments find that flux levels off at large Ram and finger spacing increases with Ram. Here we show that the convective pattern is controlled by a dispersive Rayleigh number, Rad, balancing buoyancy and dispersion. Increasing the bead size of the porous medium increases Ram but decreases Rad and hence coarsens the pattern. While the flux is predominantly controlled by Ram, the anisotropy of mechanical dispersion leads to an asymmetry in the pattern that limits the flux at large bead sizes. Plain Language Summary Pattern formation in simple physical systems is intriguing, and convection in porous media is an example that was thought to be well understood. Convection is controlled by the balance between buoyant driving forces and dissipative mechanisms such as diffusion that smear out the concentration and hence density differences. Here we use simple laboratory experiments to show that the convective pattern is controlled by a different process than previously thought. A Rayleigh number based on mechanical dispersion, which is independent of fluid properties, predicts the flow pattern of solutal convection in bead packs. Key Points The classic Rayleigh number predicts neither flux nor pattern of convection in bead packs The convective pattern is controlled by mechanical dispersion and independent of fluid properties The anisotropy of dispersion breaks the symmetry of the convective pattern and reduces the flux