MULTIPLICATIVE PROCESS IN TURBULENT VELOCITY STATISTICS - A SIMPLIFIED ANALYSIS

A lot of models in turbulence links the energy cascade process and int ermittency, the characteristic of which being the shape evolution of t he probability density functions (pdf) for longitudinal velocity incre ments. Using recent models and experimental results, we show that the flatness factor of these pdf gives a simple and direct estimate for wh at is called the deepness of the cascade. We analyse in this way the p ublished data of a Direct Numerical Simulation and show that the deepn ess of the cascade presents the same Reynolds number dependence as in laboratory experiments.