Meandering jets in a shallow fluid layer

A plane turbulent jet bounded in a fluid layer of depth H exhibits three distinct fluid zones : a near field (x/H less than 1) with classical unbounded jet behavior, a middle field with pronounced secondary circulations and well established three-dimensional turbulence, and the far field (x/H greater than 10) with large scale two-dimensional coherent structures in the form of an unsteady meandering motion. The far field flow appears to be in an asymptotic equilibrium state with a gradual growth of the length scales through turbulent diffusion. No other growth, pairing, or break-up mechanisms were observed. With increasing distance, there is a widening spectral window in which the energy transfer appears to be controlled by two-dimensional turbulence.