Onset and evolution of a wavy instability in shaken sand

Abstract

A novel small wavelength instability occurs in experiments for vertically shaken ( z = a cos( ωt)) sand, for small particle diameters d and when gas effects are important. At onset, the energy (aω) 2 gd is proportional to a d , as previously found for traveling waves. The instability begins as a surface perturbation with wavelength λ 0 ∼ 6 mm; subsequently λ grows exponentially in time.