Modelling the transitional wall-jet by using a dynamical system

A low-dimensional dynamical system has been used to model the transition process in a wall-jet. Numerical simulations of non-linear dynamics have been pursued considering the dominant interaction among triadic resonant modes. The analysed time evolutions involve the most unstable linear mode and other two-dimensional or three-dimensional modes; the dependence of the transition behaviours from different type of resonant interaction has been pointed out. For a local self-similar evolution of the mean flow, the spreading rate of the length scale has been deduced from the mean kinetic energy flux equation. The obtained results show that the development of large scale coherent structures enhances the momentum diffusion.