Settling of non-Brownian particles

Images taken during particle sedimentation (the display area is approximately 4.5 mm X 3.4 mm):

(a) A particle configuration taken 35 minutes after mixing.

(b) A superposition of five sequential images taken at 30 second intervals beginning 30 minutes after mixing, showing a turbulent looking velocity field.

(c) A particle configuration taken 5 hours after mixing.

(d) A superposition of five sequential images taken at 30 second intervals beginning 5 hours after mixing.

While the single images (a) and (c) show similar looking random configurations of particles, the corresponding velocity fluctuations in (d) are less violent than those in (b).  Evidently there are subtle configuration differences between the two times.

Particle occupancy distributions:

(a) For = 6, 2 minutes after mixing (solid circles) and 8 hours after mixing (open circles).

(b) For = 58, 2 minutes after mixing (solid squares) and 8 hours after mixing (open squares).

The solid curves represent the Poisson distribution, , for the corresponding < N >. This distribution describes the earliest measurements after mixing but not at the later times, when the experimental distribution narrows relative to the Poisson distribution. The later time data show a strong suppression of number fluctuations with increasing test volume dimension.