@article{WOS:000580889500001,
 abstract = {An array of spheres descending slowly through a viscous fluid always
clumps [J. M. Crowley, J. Fluid Mech. 45, 151 (1971)]. We show that
anisotropic particle shape qualitatively transforms this iconic
instability of collective sedimentation. In experiment and theory on
disks, aligned facing their neighbors in a horizontal one-dimensional
lattice and settling at Reynolds number similar to 10(-4) in a
quasi-two-dimensional slab geometry, we find that for large enough
lattice spacing the coupling of disk orientation and translation rescues
the array from the clumping instability. Despite the absence of inertia,
the resulting dynamics displays the wavelike excitations of a
mass-and-spring array, with a conserved ``momentum″ in the form of
the collective tilt of the disks and an effective spring stiffness
emerging from the viscous hydrodynamic interaction. However, the
non-normal character of the dynamical matrix leads to algebraic growth
of perturbations even in the linearly stable regime. Stability analysis
demarcates a phase boundary in the plane of wave number and lattice
spacing, separating the regimes of algebraically growing waves and
clumping, in quantitative agreement with our experiments. Through the
use of particle shape to suppress a classic sedimentation instability,
our work uncovers an unexpected conservation law and hidden Hamiltonian
dynamics which in turn open a window to the physics of transient growth
of linearly stable modes.},
 article-number = {041016},
 author = {Chajwa, Rahul and Menon, Narayanan and Ramaswamy, Sriram and
Govindarajan, Rama},
 doi = {10.1103/PhysRevX.10.041016},
 issn = {2160-3308},
 journal = {PHYSICAL REVIEW X},
 month = {OCT 22},
 number = {4},
 orcid-numbers = {Menon, Narayanan/0000-0003-0901-8488
Ramaswamy, Sriram/0000-0001-7726-8556},
 researcherid-numbers = {Govindarajan, Rama/ABE-6919-2020
},
 title = {Waves, Algebraic Growth, and Clumping in Sedimenting Disk Arrays},
 unique-id = {WOS:000580889500001},
 volume = {10},
 year = {2020}
}