High Reynolds-number orographic wave-breaking experiments

In this paper, we present laboratory measurements at high Reynolds numbers of the turbulence generated by breaking internal-gravity waves of flow over Gaussian-shaped obstacles. The results confirm that the flow evolution leading to wave-breaking for a flow started from rest and the ensuing large-scale flow structures in the wave-breaking region are essentially the same as observed in the low Reynolds-number laboratory experiments of Eiff and Bonneton [Eiff, O.S., Bonneton P., 2000. Lee-wave breaking over obstacles in stratified flow. Phys. Fluids 12 (6),1073-1086] and the associated direct numerical simulations of Gheusi et al. [Gheusi, F., Stein J., Eiff O.S., 2000. A numerical study of three-dimensional orographic gravity-wave breaking observed in a hydraulic tank. J. Fluid Mech. 410, 67-99]. The flow reaches a quasi-steady state during which turbulence statistics are computed in a horizontal plane intersecting the wave-breaking region. The statistics reveal a highly turbulent flow with intensities up to 20% of the free-stream velocity and spatial distributions which indicate that the underlying large-scale flow structures - toroidal vortices - are quasi-steadily aligned in the spanwise direction and that they might be shed downstream.