Interaction of a turbulent boundary layer with a bio-inspired flexible canopy

The present work explores the structure of turbulent flow over elastic micro-structures laid on an impermeable wall. The filamentous layer consists of an array of slender flush mounted flexible cylinders. The dynamic deformations of the cylinders are governed by an inextensible Kirchhoff rod model, which is well suited to model such structures: it enables control of the undeformed shape and flexibility, among other parameters to match the characteristics of the bio-inspired canopies considered in the present study. We considered a turbulent channel flow case, where the bottom wall was covered by filaments with different flexibility. Three cases were considered: rigid filaments, highly flexible filaments, and one in between. Overall, at the bottom wall a significant momentum deficit, caused by the presence of the filaments, is observed. As the bending rigidity decreases and the filaments are pushed closer to the wall, the momentum deficit increases. As a result the turbulent kinetic energy pick is amplified and moves close the top of the average location of the filament tips. DNS exploring a wider parametric range are ongoing.