Chaotic sedimentation of particle pairs in a vertical channel at low Reynolds number: Multiple states and routes to chaos

Thesedimentation of a pair of rigid circular particles in a two-dimensional vertical channel containing a Newtonian fluid is investigated numerically, for terminal particleReynolds numbers (ReT) ranging from 1 to 10, and for a confinement ratio equal to 4. While it is widely admitted that sufficiently inertial pairs should sediment by performing a regular DKT oscillation (Drafting-Kissing-Tumbling), the present analysis shows in contrast that a chaotic regime can also exist for such particles, leading to a much slowersedimentation velocity. It consists of a nearly horizontal pair, corresponding to a maximum effective blockage ratio, and performing a quasiperiodic transition tochaos while increasing the particle weight. For less inertial regimes, the classical oblique doublet structure and its complex behavior (multiple stable states and hysteresis, period-doubling cascade and chaoticattractor) are recovered, in agreement with previous work [Aidun, C. K. and Ding, E.-J., “Dynamics of particlesedimentation in a vertical channel: Period-doublingbifurcation and chaotic state, ” Phys. Fluids15, 1612 (2003)]. As a consequence of these various behaviors, the link between the terminalReynolds number and the non-dimensional driving force is complex: it contains several branches displaying hysteresis as well as variousbifurcations. For the range ofReynolds number considered here, a globalbifurcation diagram is given.

Source: Physics of Fluids - December 7, 2016 Category: Physics Authors: Romuald Verjus, Sylvain Guillou, Alexander Ezersky and Jean-R égis Angilella Source Type: research