Numerical experiments on the intermediate asymptotics of shear-free turbulent transport and diffusion. Associated similarity analysis.

A numerical experiment on the interaction between different decaying homogeneous and isotropic turbulences is described. In the absence of kinetic energy production, the intermediate asymptotics of the turbulent shear-free mixing layer can be observed. The first aim of the experiment is to verify of the existence of the intermittency or of the Gaussian asymptotic state in the case of the absence, or weak presence, of a lengthscale gradient.
The second aim is to analyse the effects that are due to the difference between the spectral distribution of the interacting turbulences, which introduces the presence of the gradient of integral scale into the initial condition.
An associated similarity analysis carried over the solution of the two-point correlation equation is also described.