SEDIMENTATION IS CONTAINER-SIZE DEPENDENT

In very dilute, bounded dispersions of identical spheres, the initial distributions of particle and fluid velocities in small containers differ enormously from those in very large ones. In the latter, local interactions are dwarfed by the massive collective influence of distant spheres. Large regions move downward or upward virtually en masse. Since particles and fluid in these clusters move with almost the same velocity, the mean of the initial distribution is scarcely affected by the much larger container size, but individual velocities can exceed the mean by one or more orders of magnitude. Experimental evidence of cluster settling, including the effect of container size, is ancient and abundant.