An actuated elastic sheet interacting with passive and active structures in a viscoelastic fluid

We adapt the classic Taylor swimming sheet set-up to investigate both the transient and long-time dynamics of an actuated elastic sheet immersed in a viscoelastic fluid as it interacts with neighboring structures. While the preferred kinematics of the sheet are specified, the flexible sheet interacts with the surrounding fluid and other structures, and its realized kinematics emerges from this coupling. We use an immersed boundary framework to evolve the Oldroyd-B/Navier-Stokes equations and capture the spatial and temporal development of viscoelastic stresses and sheet shape. We compare the dynamics when the actuated sheet swims next to a free elastic membrane, with and without bending rigidity, and next to a fixed wall. We demonstrate that the sheets can exploit the neighboring structures to enhance their swimming speed and efficiency, and also examine how this depends upon fluid viscoelasticity. When the neighboring structure is likewise an actuated elastic sheet, we investigate the viscoelastic dynamics of phase-locking.