RESONANT ENHANCED DIFFUSION IN TIME-DEPENDENT FLOW

Explicit examples of scalar enhanced diffusion due to resonances betwe en different transport mechanisms are presented. Their signature is pr ovided by the sharp and narrow peaks observed in the effective diffusi vity coefficients and, in the absence of molecular diffusion, by anoma lous transport. For the time-dependent flow considered here, resonance s arise between their oscillations in time and either molecular diffus ion or a mean flow. The effective diffusivities are calculated using m ultiscale techniques.