Structures and transition in a high Reynolds number experiment

We present a brief review of experimental results obtained in high Reynolds number flows using Helium gas as the working fluid. We focus on measurements of the skewness and the flatness of the velocity derivative, and in particular their evolution with the Reynolds number. A transition, observed at R λ 700, is discussed. In the second part, we analyze the structures associated with high velocity gradients, which we identify as worms ; we finally present a detailed analysis of the evolution of their mean size, their number and their velocity increment with Reynolds number