Flow-induced loading on and unsteady flow structure in the wake of bluff perforated plates at zero incidence

Flow over rectangular plates positioned at zero incidence can result in high-amplitude forces on the plates. In this study, we apply particle image velocimetry (PIV) and direct force measurements to investigate the effect of transverse perforations on the flow-induced loading on and the flow structure in the near-wake of the plates. We compare plates with different characteristic diameter of the perforations, as well as a reference configuration without perforations, in terms of the spectra of the flow-induced forces, frequencies of the trailing edge vortex shedding and boundary layer profiles at the trailing edge at different planes across the perforation patterns for a range of inflow velocities. The three-dimensionality of the near-wake of the perforated plate is related to the proximity of the individual perforations to the trailing edge of the plate. In the vicinity of the perforations, transverse oscillations of the flow velocity in the wake become suppressed as the diameter of the perforations increases.