Quantitative Analysis of an Invading-Fluid Invasion Front under Gravity

Abstract

We report a detailed quantitative comparison between experimental measurements of the structure of a nonwetting fluid invasion front into a porous medium and a gradient percolation model accounting for the influence of gravity. The 2D correlation function of the invaded area in horizontal cuts follows a universal behavior at short distances in the fractal domain in good agreement with numerical predictions. Variations with the cut height of the mean saturation and of the crossover length between the fractal and the Euclidean domains can also be fitted precisely with theoretical gradient percolation curves.