Intermittency of Fluid Imbibition in Disordered Media
Abstract
We present an experimental study of the global velocity spatially averaged over the length scale l, Vl(t), of an air-liquid interface during the forced-flow imbibition of a viscous wetting liquid in a disordered medium. Thanks to a high resolution fast camera, we have followed directly the imbibition front and observed a complex dynamics, governed by power-law distributed avalanches on a wide range of durations and sizes [1, 2]. We characterize here this intermittent behavior by studying the statistical properties of the global velocity increments DVl(x) / Vl(t + x) - Vl(t) for various time lags x. In particular we show that the shape of the PDF of DVl(x) evolve with increasing x from fat tail exponentially stretched PDFs towards a Gaussian PDF above a characteristic time xc, which corresponds to the characteristic avalanche duration.
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