The mixing transition in turbulent flows

Data on turbulent mixing and other turbulent-flow phenomena suggest that a (mixing) transition, originally documented to occur in shear layers, also o ccurs in jets, as well as in other flows and may be regarded as a universal phenomenon of turbulence. The resulting fully-developed turbulent flow req uires an outer-scale Reynolds number of Re = U delta/nu greater than or sim ilar to 1-2 x 10(4), or a Taylor Reynolds number of Re-T = mu' lambda(T) / nu greater than or similar to 100-140, to be sustained. A proposal based on the relative magnitude of dimensional spatial scales is offered to explain this behaviour.