z=asin (ωt) where z is the vertical position,a is the amplitude and ω=2f
where f is the frequency. The frequency was fixed at 10 Hz. The amplitude could be varied from 0 to 10 mm. The granular material consisted of glass spheres, with bulk static density=(1440±10) kg/m3, sieved between 180 and 300m woven
mesh sieves (the grain size distribution was measured to be roughly Gaussian, with the peak diameter at 270m and standard deviation of 50m). Grains were contained in a Plexiglas cell depictedFig. 3B, shaped as an U-tube with square cross-section1.Experiments were done at atmospheric pressure. The total mass of grains
was (0.1244±0.0001) kg, capable of filling one of the branches of the U-tube from bottom to top.