Title: Instabilities in settling array of discs

Author (Talk): Rahul Chajwa, Tata Institute of Fundamental Research

Abstract:

Collective stokesian sedimentation is a challenging problem in the physics of many-body system with long range interactions. It offers rich dynamical behaviour when particles have nontrivial shapes, due to coupling of geometry and flow. Our experiments demonstrate the effect of shape anisotropy at the level of two particles, finding a variety of bound and scattering orbits for settling pair of discs. These orbits can be understood by a mapping to Kepler problem of planetary motion, through the emergence of an effective Hamiltonian for this wholly dissipative system. This pair interaction serves as a building block for collective sedimentation of disc shaped objects. In this talk I will summarise our experimental finding and theoretical understanding of the instabilities associated with disc shaped particles driven in a viscous fluid.