SCALAR INTERMITTENCY IN THE VARIATIONAL THEORY OF TURBULENCE

The evolution of the probability density function (pdf) of temperature differences (passive or active scalar): T(x + r) - T(x) versus the sc ale r is considered on the point of view of the variational theory. Th e pdf at scale r appears as a superposition of rescaled large-scale pd fs, with a log-normal distribution of the scaling factors theta. As in the velocity case the variance of this log-normal distribution behave s as a power law versus r, the exponent going to zero as the Reynolds or Grasshof numbers go to infinity.