The effect of stabilization has been investigated experimentally when a nonwetting fluid is displacing a wetting fluid with the same viscosity in a two-dimensional porous medium. Experiments were done at different injection rates, with capillary numbers ranging from 10 Ϫ7 to 10 Ϫ4 . The features of the front between the liquids were analyzed and found similar to those observed from invasion percolation models including a spatial gradient in the average pore threshold value, and gravitationally stabilized experiments. Front and structure of the trapped clusters of the invaded fluid at different capillary numbers are self-similar with the fractal dimensions D b ϭ1.33 and D b m ϭ1.85, respectively. The dependence of the front width w s on the capillary C a was found to be consistent with a power law w s ϳC a Ϫ␣ , with ␣ϭ0.6. The dynamic exponent ␤ d Ϸ0.8 describing front width evolution as a function of time was determined by collapsing the density-density correlation function data. An analytical argument is presented to support the stabilization of the front owing to the viscous effects. ͓S1063-651X͑96͒05012-X͔ PACS number͑s͒: 47.55.Mh, 05.40.ϩj, 47.55.Kf

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In this paper a method for the estimation of the curvature along a condensed phase interface is presented. In a previous paper in this journal [1] a mathematical relationship was established between this curvature and a template disk located at a given point along the interface. The portion of the computed area of the template disk covering one of the phases was shown to be asymptotically linear in the mean curvature. Instead of utilizing this relationship, an empirical approach was proposed in [1] in order to compensate for discrete uncertainties. In this paper, we show that this linear relationship can be used directly along the interface avoiding the empirical approach proposed earlier. Modifications of the algorithm are however needed, and with good data smoothing techniques, our method provides good quantitative curvature estimates.