Periodic saltation under extreme tidal currents: an experimental study

Gaspard Minster (1, 2) , France Floc'H , Alexandre Valance , Nicolas Le Dantec , Amandine Nicolle (3, 2) , Jean-François Filipot , Benoit Zerr (1, 2)

1 Lab-STICC_ENSTAB_CID_PRASYS
2 Pôle STIC_OSM
3 AD2M - Adaptation et diversité en milieu marin

In extreme tidal environment and specifically in the Alderney race (English Channel, France), the ambition to install hydrokinetic turbines requires knowledge on the pebbles concentration in the water column. Some evidences of the presence of such coarse sediments at one meter above the bed have been found. An experimental study is realized in a free surface flume for high Stokes number. With fast camera the trajectories of hundreds of spherical particles are analyzed. This study focuses on the characterization of the critical Shields number to intermittent and saltation regime and on the coefficient of restitution between the impact and the rebound velocity . The critical Shields number is identified experimentally at 0.2. The restitution coefficient shows little dependence on the impact angle. Finally, the experimental maximum height reached by the spherical particles proves that lift and inertia forces are not negligible.

Mots clés: Saltation; hydrodynamics; Experimental modelling; Shields number; Restitution coefficient; High Stokes number

Domaines: Physique [physics]; Océan, Atmosphère

Gaspard Minster, France Floc'H, Alexandre Valance, Nicolas Le Dantec, Amandine Nicolle, et al.. Periodic saltation under extreme tidal currents: an experimental study . Coastal Dynamics, Jun 2017, Copenhague, Denmark. ⟨hal-01698481⟩