Numerical Investigation on the Effects of Material Properties on the Evolution Mechanism of Rayleigh–Taylor Instability in Porous Media

ABSTRACT

This study systematically investigates the evolution mechanism of Rayleigh–Taylor instability (RTI) in porous media using a lattice Boltzmann model at the representative elementary volume (REV) scale. The results indicate that miscible RTI in REV‐scale porous media is governed by a structural–transport–force coupling mechanism. Porosity mainly regulates the effective flow area and structural resistance, whereas the Darcy number controls permeability‐related resistance and inertial flow reorganization. The Rayleigh number mainly reflects the intensity of buoyancy‐energy input. By analyzing the distributions of the horizontal and vertical force components, Fx and Fy , respectively, the present study shows that force‐field symmetry breaking is closely associated with vortex formation, interface deformation, and fingering development. Under the present numerical configuration, the transition from resistance‐limited diffusion to buoyancy‐driven convection appears around ε  ≈ 0.35, Da ≈ 10 ⁻⁴ , and Ra ≈ 10 ⁵ . These values are interpreted as case‐dependent transition ranges rather than universal critical constants. The findings may provide useful guidance for controlling mixing and heat/mass transfer in porous‐media systems, including CO ₂ geological storage, miscible displacement, catalytic porous layers, and porous heat‐transfer structures.