Dissipative interactions between particles in shear flow

We present an experimental study of a low-Reynolds number shear flow carrying particles. The flow is nearly two-dimensional due to stable stratification of the fluid, with the particles occupying a planar neutral buoyancy layer. While both the two- and three-particle interactions show a degree of irreversibility, the three-particle interactions demonstrate apparently chaotic behavior, where small variations in the initial conditions of the experiment (i.e., particle positions) lead to large changes in the final state of the experiment. Moreover, a detailed knowledge of the trajectory of each particle in the triplet is required to relate the final particle order to the initial positions. Results of experiments with particles of different shapes (spherical, ellipsoid, etc.) are also discussed.