The mechanism behind VIV onset on rectangular cylinders with porous coverings: an experimental and numerical study

This study investigates the aeroelastic effects of a porous envelope on an elongated rectangular cylinder with an aspect ratio of 3.33. The addition of a porous covering to a solid structure allows airflow into the gap between the two surfaces, altering the dynamics of the separated shear layer, with potential for vortex-shedding (VS) suppression. An experimental campaign, complemented by 3D CFD simulations, was conducted to examine the role of the porous covering in VS behavior and the vortex-induced vibrations (VIV) of the structure. Specifically, large eddy simulation (LES) was employed to capture the evolution of the flow field and to assess how the permeable covering affects the forcing mechanisms induced by VS. Results highlight that the onset of VIV is governed by the spatial correlation of the instantaneous pressure field, reaffirming the state-dependent nature of this phenomenon.