Dynamique tourbillonnaire - Application à l'impact environnemental de structures immergées

Abstract : The study was performed experimentally. The vortices are generated by interaction between a monochromatic wave and a horizontal thin plate used as vortex generator. Their characterisation has been done in two and three dimensions. The two-dimensional vortex dynamics is characterized using PIV measurements. We observed the formation of downstream and upstream vortex pairs which are mutually advected toward the flume bottom and the free surface respectively. These evolutions are characterised through mean vortex trajectories computed thanks to λ2 criteria. It shows the presence of two stagnation point at the flume bottom due to the vortex pair advection and to the presence of two adjacent recirculation cells under the plate. These points would be a location of scouring phenomenon in the case of a sea bed. The three-dimensional vortex destabilisation has been studied thanks to the stereo-videography. The vortex cores are visualised with hydrogen micro bubbles generated at the edges of the plate by electrolysis. The deformation modes study, using a Fourier and a wavelet analysis, revealed that the deformation modes vary over the wave period. Strong axial velocity had been visualised on the vortex cores from the beginning of their development. These velocities are characteristics of strong destabilisations and vortex bursting.
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Adrien Poupardin. Dynamique tourbillonnaire - Application à l'impact environnemental de structures immergées. Mécanique des fluides [physics.class-ph]. Université du Havre, 2012. Français. ⟨tel-00832174⟩

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