Lecturer: Mr. Tomer Goldfriend
Affiliation:
Raymond & Beverly Sackler School of Physics & Astronomy,
Tel Aviv University
Abstract:
Sedimentation, the settling of colloidal objects
under gravity, involves long-ranged flow-
mediated interactions among the objects.
Consequently, sedimenting suspensions exhibit
a complex many-body dynamics with strong
fluctuations, even in the case of athermal
(non-Brownian) objects at zero Reynolds
number.
We study the sedimentation of objects of
irregular shape by employing a fluctuating
hydrodynamic model. We find that the
anisotropic coupling between the external
drive, hydrodynamic interactions, and objects'
orientations, directly suppresses concentration
and velocity fluctuations. This allows the
suspension to avoid the anomalous
fluctuations predicted for suspensions of
spheres or symmetric spheroids. The
suppression of concentration fluctuations
leads to a dynamic, hyperuniform structure.
For certain object shapes, the anisotropic
response may act in the opposite direction,
destabilizing uniform sedimentation.