Reynolds number dependence of the intermittency exponent in fully developed turbulence

Jochen Cleve (MPIPKS Dresden), Thomas Dziekan (TU Dresden), Martin Greiner (Siemens Muenchen)

The guiding principle for the inertial range dynamics of fully developed turbulence is scale invariance. The important
question which are good fields and good observables for this has so far not attracted much attention. A careful analysis
of hot-wire time series data reveals that velocity pdfs and structure functions do not reveal a strict scaling and that
heuristic methods like Extended Selfimilarity are misleading. It is the surrogate energy dissipation field together with
two-point observables, like two-point correlators and cumulants, which show a clear and rigorous scaling, revealing that
the intermittency exponent is a function of the Reynoldsnumber. Once several observational effects are properly taken
into account, empirical random multiplicative energy cascade models give a very satisfying description of these findings
and allow for a unification of several data-driven models, which previously have appeared to be in conflict with each