Scalar Beltramization in turbulent flows
Résumé
We show that in turbulent scalar mixing the advection is strongly suppressed with respect to its Gaussian estimate. This effect is particularly important in the small scales. Results are given for different Schmidt numbers, illustrating the persistency and universality of the phenomenon. The link with the generation of passive scalar fronts is discussed and it is argued that scalar fronts are the consequence of the underlying suppression of nonlinearity observed in a wide class of flows for which the dynamics are governed by quadratic nonlinearities or pseudo-nonlinearities.
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