DEPOSITION-RATE EFFECTS ON ROUGH SURFACES FORMED BY SEDIMENTING PARTICLES

The quasi-two-dimensional sedimentation of silica particles in a visco us fluid results in quasi-one-dimensional surfaces. These surfaces are rough on all length scales between the particle size and the cell siz e, but different roughness exponents an observed in two well-defined l ength scale regimes. Hydrodynamic forces should play an important role in determining which, if either, length scale regime shows universal properties. The role of these hydrodynamic forces can be controlled th rough control of the deposition rate of particles into the cell. A ran ge of different deposition rates has been examined, and a clear upward trend was observed in the scaling exponent found at long length scale s, while the scaling exponent found at short length scales remained re latively constant and very consistent with results of previous experim ents with a fixed number of particles but wherein cell length, cell wi dth, and fluid viscosity were all varied with no effect on observed in terfacial roughness.