Anomalous Roughening of Viscous Fluid Fronts in Spontaneous Imbibition

摘要

We report experiments on spontaneous imbibition of a viscous fluid by a model porous medium in the absence of gravity. The average position of the interface satisfies Washburn's law. Scaling of the interface fluctuations suggests a dynamic exponent z approx= 3, indicative of global dynamics driven by capillary forces. The complete set of exponents clearly shows that interfaces are not self-affine, exhibiting distinct local and global scaling, both for time (β = 0.64 ± 0.02, β~* = 0.33 ± 0.03) and space (α = 1.94 ± 0.20, α_(loc) = 0.94 ± 0.10). These values are compatible with an intrinsic anomalous scaling scenario.