IMT Seminar - Anne Juel

Abstract

The handling and processing of microscale materials, which is routinely performed in a liquid environment, involves a rich variety of processes in the Stokes limit of vanishing inertia, e.g., the segregation of graphene by centrifugation, blood testing methods, microalgae harvesting, and the separation of microplastics from natural sediment
 
Elastohydrodynamic coupling can radically alter the inertialess transport of particles as illustrated by the buckling, crumpling and tumbling of flexible sheets in simple shear flow.
 
We study the settling of an elastic sheet under its own weight. The sedimentation flow generates viscous loading on the sheet which may deform or reorient, and this can in turn alter the flow. We find that unlike a slender flexible fibre, an elastic sheet sedimenting in a large tank does not evolve towards a steady state and instead exhibits a myriad of complex reorientation and sedimentation paths depending on its initial orientation.
 
To unravel these complex dynamics, we select a stiffness of sheet that leads to U-bent shapes during settling and study its behaviour by comparison with the settling of equivalent rigid shapes, which we characterise with experiments and numerical simulations.
 
We find that in addition to the pitching and rolling motions of the rigid sheet, the elastic sheet can reconfigure its spine or invert its curvature. Using a neural network to interpolate the experimental data, we determine a mobility matrix for the sheet depending on its shape and compare rates of deformation and reorientation.
 
The model suggests that the elastic disk is likely to exhibit a periodic cycle of rolling to an upright orientation, followed by pitching and subsequent spine reconfiguration.
 
Our results highlight the importance of particle shape in inertialess sedimentation and provide the fundamental framework to build an understanding of suspensions of particles of arbitrary shape such as microplastics.

Speaker

Anne Juel is Professor of Physics of Fluids at the University of Manchester and has been the Director of the Manchester Centre for Nonlinear Dynamics.
 
She obtained her D.Phil from Oxford University in 1998 and was a post-doctoral fellow at UT Austin and Manchester before her appointment to a faculty position at the University of Manchester in 2001.
 
Her research focuses on fluid-structure interaction and interfacial phenomena in complex fluids and soft matter.
 
She is a Fellow of the American Physical Society, an Associate Editor of JFM and sits on the editorial boards of Annual Reviews of Fluids Mechanics and PRSA.

Tags

Multiscale Thermofluids