Viscous fingering in granular materials in a vertical Hele-Shaw cell

The dynamics of the air-granular interface has been studied in a quasi-two-dimensional vertically aligned Hele-Shaw cell experimentally. The air was pressed into the cell at the bottom through a single hole and the development of the upward propagating fingers was analyzed with the help of fast video recording. The behavior of the system was analyzed as a function of the applied air pressure, the grain size and the grain shape by using spherical glass beads or sorted sand particles.