Time‐dependent mixing in stratified Kelvin‐Helmholtz billows: Experimental observations

Quantitative time‐dependent laboratory measurements are made of the irreversible mixing caused by the development, saturation and turbulent breakdown of Kelvin‐Helmholtz (KH) billows in an initially stable two‐layer stratified shear flow of miscible fluids. The measurements are obtained using a light attenuation technique. Irreversible mixing is found to be strongly dependent on the life‐cycle of the flow, in particular the characteristics of large‐scale, quasi‐two‐dimensional billow merging events, which stir the flow and then trigger mixing during turbulent transition.