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Abstract:
We have studied spontaneous imbibition fronts generated by capillary rise between two roughened glass plates, the separation d of which varied between 10 and 50 μm. Perfect agreement with Washburn’s law was obtained. We have determined the roughness exponent χ of the fronts, and found χ=0.81±0.01 for small length scales. Above a certain crossover length ξ, it reached χ=0.58±0.04, as predicted by the quenched noise Kardar-Parisi-Zhang equation. The crossover length is found to scale with the plate separation as d√, as predicted by recent models which properly include nonlocal dynamics effects on the front. We believe this to be the first clear identification of crossover from nonlocal to local dynamics.