Transition Toward Developed Turbulence

Using an axisymmetric jet with helium at low temperature we have studied the velocity intermittency on a large range of Taylor scale based Reynolds number R_λ. The results show, for the first time, evidence for a transition between two types of turbulence in a jet. Above the transition (R_λ>180) a clear separation occurs between small and large scales. In the intermediate range, the existence of a Reynolds dependent scaling law is confirmed. It illustrates the way in which viscosity can have some influence up close to the integral scale in developed turbulent flows.