Study of the mixing layer from the point of view of two-dimensional turbulence

The dynamics of large coherent structures in the mixing layer is examined from the point of view of two-dimensional turbulence, both by direct numerical simulations and with the aid of the EDQNM stochastic model. The predictability theory leads in this case to a mechanism of return to three-dimensionality for a given coherent structure. One suggests that, after their 'explosive' destruction, the large structures are recreated by the linear instability of the inflexional mean shear. The dynamics of the mixing layer could then be governed by an intermittent transition between two states, 'coherent' and 'incoherent'.