Short circuits in the Corrsin–Obukhov cascade

Experiments show that a blob of scalar released in the inertial range of scales of a turbulent medium is rapidly converted into a set of disjointed sheets whose spectrum exhibits a k(-1) shape for wave numbers larger than the injection wave number 1/d. The sheets diffusive uniformization onsets at a time t(s)=(d/u)f(Sc) with f(Sc)similar to ln(Sc) function of the injection time of the blob in the medium d/u, of the Schmidt number Sc, independently of the Reynolds number. This time is appreciably smaller than the time needed to cross the Kolmogorov cascade, which is "bypassed" by a strong and constant stretching rate acting at the injection scale. (C) 2001 American Institute of Physics.