title: Anomalous roughening of viscous fluid fronts in spontaneous imbibition.
abstract: 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 approximately 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 (beta = 0.64 +/- 0.02, beta(*) = 0.33 +/- 0.03) and space (alpha = 1.94 +/- 0.20, alpha(loc) = 0.94 +/- 0.10). These values are compatible with an intrinsic anomalous scaling scenario.
authors.affiliation: Experimentalphysik I, Universität Bayreuth, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Soriano
authors.forename: A
authors.initials: A
authors.lastname: Mercier
authors.forename: R
authors.initials: R
authors.lastname: Planet
authors.forename: A
authors.initials: A
authors.lastname: Hernández-Machado
authors.forename: M A
authors.initials: MA
authors.lastname: Rodríguez
authors.forename: J
authors.initials: J
authors.lastname: Ortín