Fluctuations in fluid invasion into disordered media

Phys Rev Lett. 2007 Feb 2;98(5):054502. doi: 10.1103/PhysRevLett.98.054502. Epub 2007 Jan 31.


Interfaces moving in a disordered medium exhibit stochastic velocity fluctuations obeying universal scaling relations related to the presence or absence of conservation laws. For fluid invasion of porous media, we show that the fluctuations of the velocity are governed by a geometry-dependent length scale arising from fluid conservation. This result is compared to the statistics resulting from a nonequilibrium (depinning) transition between a moving interface and a stationary, pinned one.