Author(s): Francesca De Serio; Rosangela Basile

Linked Author(s): Francesca De Serio

Keywords: Long waves; Vorticity; Turbulent coherent structures; Wavelets

Abstract: Storm surges or floods, occurring more and more frequently especially because of climate change, significantly impact marine and fluvial structures, such as offshore piles or bridges‘ piers. This kind of long waves can be assumed quite similar to solitary waves, considering their large periods and lengths. Besides the inertia and drag forces that they generate on the structure, also the production of turbulent eddies downstream the obstacle is relevant, as it may affect both an erodible bottom and the ecosystem. The present study describes a medium-scale experiment, where two different long waves were generated in a flume and superimposed to a stationary current, in presence of a couple of rigid emergent cylinders. We used a Particle Image Velocimetry (PIV) to acquire the velocity measurements, providing instantaneous flow velocity vectors on selected 2D planes. For each experimental condition, the time-varying velocity fields neighboring the cylinders were processed and examined to detect the phase-averaged wave behavior and the vorticity spreading. A wavelet based technique was also adopted. In this way it was possible to deduce how the transit of the wave, especially of its crest, affects the detachment of coherent turbulent eddies downstream of the cylinder.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221066

Year: 2022