Spreading of a density front in the K\"untz-Lavall\'ee model of porous media

TL;DR

This study reexamines the spreading of a density front in a porous media model, revealing that normal diffusion and hydrodynamic flow, not anomalous diffusion, govern the front's behavior, impacting interpretations of recent experimental results.

Contribution

It demonstrates that the apparent anomalous diffusion observed in previous studies is actually due to hydrodynamic flow, challenging prior assumptions.

Findings

Front evolution is controlled by normal diffusion and flow.

Hydrodynamic flow enhances apparent front speed.

Recent experiments attributing spreading to anomalous diffusion should be reconsidered.

Abstract

We analyze spreading of a density front in the K\"untz-Lavall\'ee model of porous media. In contrast to previous studies, where unusual properties of the front were attributed to anomalous diffusion, we find that the front evolution is controlled by normal diffusion and hydrodynamic flow, the latter being responsible for apparent enhancement of the front propagation speed. Our finding suggests that results of several recent experiments on porous media, where anomalous diffusion was reported based on the density front propagation analysis, should be reconsidered to verify the role of a fluid flow.