SEDIMENTATION OF GLASS BEADS UNDER THE INFLUENCE OF GRAVITY

Abstract

The quasi-two-dimensional sedimentation of 0.06 cm diameter silica spheres in viscous oil (between glass plates separated by a 1 mm gap) results in quasi-one dimensional rough surfaces. These surfaces are rough on all length-scales between the particle size and the cell size, but different roughness exponents are observed in each of two well defined regimes (αs=0.81±0.03 for L≤2 cm and αl=0.92±0.05 for L≥2 cm). The dynamical exponent, β, is measured to be 0.48±0.16. The role and range of hydrodynamic forces must be considered before this system can be related to available rough interface theories. A first attempt at assessing the effect of hydrodynamics yields a noise spectrum whose probability distribution is close to Gaussian (with significant excess of large fluctuations) and whose correlation function resembles that measured for density-density correlations in the oil far above the growing interface.