Water surface response to turbulent flow over a backward-facing step

The water surface response to subcritical turbulent flow over a backward-facing step (BFS) is studied via high-resolution large-eddy simulation (LES). LES method validated first using data of previously reported experiments. LES-predicted decomposed into different types gravity waves as well turbulence-driven forced waves. Analysis the reveals interplay between low-frequency large-scale turbulence structures, which are result separation from and reattachment behind step, dynamics surface. deformation mainly freely propagating waves, owing in form rollers and/or hairpin vortices. Gravity with zero group velocity define characteristic spatial temporal scales deformations at higher frequencies, while large eddies determine their modulation. These confined lateral bands that propagate downstream following advection near-surface streamwise vortices (rollers) shed step. Steeper observed regions negative perturbation gradient down-welling, larger rollers, associated thin isolated high vorticity near investigation such complex has shown decomposition fluctuations its physical components may be used identify underlying structure.