On the influence of bed roughness on saltation in inertial regime

Gaspard Minster (1, 2, 3) , France Floc'H (4) , Alexandre Valance (5) , Nicolas Le Dantec (6, 4) , Amandine Nicolle (3, 7, 8) , Benoit Zerr (3, 9)

1 Lab-STICC_ENSTAB_CID_PRASYS
2 Lab-STICC - Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance
3 ENSTA Bretagne - École Nationale Supérieure de Techniques Avancées Bretagne
4 GEO-OCEAN - Geo-Ocean
5 IPR - Institut de Physique de Rennes
6 IUEM - Institut Universitaire Européen de la Mer
7 STIC - Département STIC [Brest]
8 ADMM - Adaptation et diversité en milieu marin
9 Lab-STICC_ROBEX - Equipe ROBotics for EXploration

In extreme tidal environment, occurrences of saltating pebbles have been observed. The ambition to instal hydrokinetic turbines in such environment requires knowledge on the presence of pebbles in saltation in the water column because they can damage the structures. An experimental study is realized in a free-surface flume with no slope and different bed roughnesses as in marine environment. With fast camera the trajectories of hundreds of spherical particles are analysed. Our study deals with saltation in the inertial regime (i.e., large Stokes number) over fixed beds with various roughnesses. In inertial regime, the bed roughness has more influence on the collision process and the trajectory of the particles than for non-inertial motion where viscous forces play a key role. Jump height and length increase with bed roughness, with height increasing quicker than length leading to a more vertical trajectory for higher bed roughness. The vertical restitution coefficient is shown to increase with bed

Keywords: bed roughness; coarse sediment; critical Shields; inertial regime; saltation

Domains: Environmental Sciences; Physics [physics]

Gaspard Minster, France Floc'H, Alexandre Valance, Nicolas Le Dantec, Amandine Nicolle, et al.. On the influence of bed roughness on saltation in inertial regime. Earth Surface Processes and Landforms, 2024, 49 (4), pp.1303-1315. ⟨10.1002/esp.5767⟩. ⟨hal-04419645⟩