Demonstrating invasion percolation with a table-top experiment

This paper highlights in an historical perspective a seminal "table-top" experiment [1] which, in the 80's, was one of the first experimental demonstrations of the relevance of invasion percolation to describe quasi-static drainage of a porous medium. This experiment involves the invasion of a crushed glass packing by molten Wood metal with a large influence of gravity. To account for it, data are compared to predictions of the gradient invasion percolation model in which the effect of buoyancy is modeled by a gradient of the percolation parameter. Experimental results agree well with 3D numerical simulations [2] based on this model. This demonstrates that such simple experiments using limited equipment may validate complex physical mechanisms. It is argued that while the availability of refined new techniques may seem to make this approach obsolete, such experiments remain needed to obtain pioneering results and to open new research fields. This conclusion aligns with Etienne Guyon's tireless action to initiate table-top experiments providing fundamental physics results.