Entrainment induced by waves at a density interface impinged by a turbulent jet

Abstract: Using water/salty-water laboratory experiments}, we investigate the mechanism of erosion by a turbulent jet impinging on a density interface, for moderate Reynolds and Froude numbers. Contrary to previous models involving baroclinic instabilities, we show that the entrainment is driven by interfacial gravity waves, which break and induce mixing. The waves are generated by the turbulent fluctuations of the jet and are amplified by a mechanism of wave-induced stress . Based on the physical observations, we introduce a scaling model which varies continuously from the $Fr_i^3$ to the $Fr_i$ power law from small to large Froude numbers, in agreement with some of the previous laboratory data.