STOCHASTIC-TRANSITION INTERMITTENCY IN PIPE FLOWS - EXPERIMENT AND MODEL

New experimental results at the onset of turbulence in a gravity-drive n pipe flow are presented, and a simple phenomenological model is intr oduced to describe the intermittent behavior observed. In this model s lugs are stochastically produced at the pipe inlet, and the decrease i n velocity due to turbulent friction is taken into account. The presen t approach shows that stochastic arguments account well for several ex perimental observations at low intermittency factors. In particular, i t is shown that special intermittency routes to chaos are not needed t o explain the exponentially decaying inverse cumulative distribution o f laminar times.