STRUCTURES AND TRANSITION IN A HIGH REYNOLDS-NUMBER EXPERIMENT

We present a brief review of experimental results obtained in high Rey nolds number flows using Helium gas as the working fluid. We focus on measurements of the skewness and the flatness of the velocity derivati ve, and in particular their evolution with the Reynolds number. A tran sition, observed at R-lambda approximate to 700, is discussed. In the second part, we analyze the structures associated with high velocity g radients, which we identify as ''worms''; we finally present a detaile d analysis of the evolution of their mean size, their number and their velocity increment with Reynolds number. (C) Elsevier, Paris.