Vortex Induced Vibrations Analysis of a Cantilevered Blunt Plate by Proper Orthogonal Decomposition of TR-PIV and Structural Modal Analysis

International audienceThe present work focuses on the experimental characterization of the vortex shedding and on the induced vibrations of a cantilevered blunt rectangular aluminum plate of chord to thickness ratio 16, immersed in a uniform water flow in the hydrodynamic tunnel of the French Naval Academy Research Institute. Experiences have been conducted for Reynolds numbers Re (based on chord length) ranging from 2.5 × 10^5 to 10.5 × 10^5 at zero degrees incidence. Special attention has been paid to the interaction of the structural response and the flow dynamics at the twisting resonance. For this purpose, wake structures have been analyzed by Time Resolved Particle Image Velocimetry (TR-PIV) and the structural response of the plate has been examined by laser vibrometry. The von Karman vortex street has been characterized by statistical analysis and Proper Orthogonal Decomposition of PIV velocity fields and the structure is analyzed through modal analysis. The near-wake’s structure has been examined for three different Reynolds numbers: (i) at Re = 3.0 × 10^5, corresponding to vortex induced structural response at constant Strouhal number; (ii) at Re = 4.5 × 10^5, corresponding to mechanical resonance but dissociated vortex shedding and (iii) at Re = 5.4 × 10^5, corresponding to lock-in of the vortex shedding at the mechanical resonance. At Re = 4.5 × 10^5, at mechanical resonance, it reveals the occurrence of an energy transfer between the shear layer and the bubble wake vortex which cancels synchronization of the structural vibration with the von-Karman vortex street