Statistical conservation laws in turbulent transport - art. no. 164502

We address the statistical theory of fields that are transported by a turbu lent velocity field, both in forced and in unforced (decaying) experiments. With very few provisos on the transporting velocity field, correlation fun ctions of the transported field in the forced case are dominated by statist ically preserved structures. In decaying experiments we identify infinitely many statistical constants of the motion, which are obtained by projecting the decaying correlation functions on the statistically preserved function s. We exemplify these ideas and provide numerical evidence using a simple m odel of turbulent transport. This example is chosen for its lack of Lagrang ian structure, to stress the generality of the ideas.