Frictional fingers in gravity

Pattern formation of frictional fingers in a gravitational potential

Jon Alm Eriksen, Renaud Toussaint, Knut Jørgen Måløy, Eirik Flekkøy, Olivier Galland, and Bjørnar Sandnes
Phys. Rev. Fluids 3, 013801 – Published 3 January 2018

Gravity induces parallel growth of finger structures which forms when air displaces a granular-liquid mixture. The alignment direction, which varies between horizontal and vertical, is explained by the interplay between surface tension, yield stresses, and the hydrostatic potential.