title: Sub- and superdiffusive molecular displacement laws in disordered porous media probed by nuclear magnetic resonance.
abstract: Hydrodynamic dispersion of water flowing through porous glasses with nominal pore sizes in the range 40 to 160 micrometers was studied with the aid of a pulsed gradient nuclear magnetic resonance technique compensating for coherent flow velocities. The crossover from effectively subdiffusive mean square displacement, <Z2> proportional variant t0.84, in the absence of hydrodynamic flow to a superdiffusive, almost ballistic power law, <Z2> proportional, variant t1.95, at the highest flow rates was observed. At intermediate flow rates, a gradual conversion between these two limiting power laws occurs. As a function of the Péclet number, the effective dispersion coefficient is in accordance with a power law with an exponent 1.2.
authors.affiliation: Sektion Kernresonanzspektroskopie, Universität Ulm, 89069 Ulm, Germany.
authors.forename: Yujie
authors.initials: Y
authors.lastname: Li
authors.forename: German
authors.initials: G
authors.lastname: Farrher
authors.forename: Rainer
authors.initials: R
authors.lastname: Kimmich