Mercredi 12 février à 11h00 ; salles des séminaires IRPHE
To enhance the understanding of the dynamics of anisotropic solid bodies moving through a fluid in inertial regime, this study investigates both the motion of isolated cylinders and the collective behaviour of cylinder groups, focusing on the influence of aspect ratio, density, Archimedes number, and other key parameters.
For isolated cylinders, a novel force model was developed, demonstrating that large oscillation amplitudes generate an average inertial force that significantly affects the falling velocity. The analysis revealed the necessity of incorporating a history force, in addition to drag and lift, within the Kelvin–Kirchhoff framework. Under certain conditions, an upward counter-flow was observed to stabilise the trajectories, providing new insights into flow-body interactions. The settling of group of cylinders was found to be even more complex, driven by strong hydrodynamic coupling, inter-body collisions, and orientation effects. Despite these complexities, coherent patterns emerged. The groups fall with constant average velocities, forming intricate internal structures influenced by control parameters. Remarkably, the development of concentrated ”streams” within the groups introduced significant heterogeneity. A predictive model, based on small-scale heterogeneities, was formulated to estimate the overall falling velocity. Additionally, scaling laws derived from velocity fluctuations captured the interplay between intrinsic body mobility and wake-induced entrainment effects.
These findings shed light on the intricate interplay of forces and structures in anisotropic body–fluid systems, advancing the understanding of their underlying dynamics.