Slow dynamics in a turbulent von karman swirling flow

An experimental study of a turbulent von Karman flow in a cylinder is presented. The mean flow is stationary up to a Reynolds number Re = 10(4) where a bifurcation takes place. The new regime breaks some symmetries of the problem and becomes time dependent because of equatorial vortices moving with a precession movement. In the exact counterrotating case, a bistable regime appears and spontaneous reversals of the azimuthal velocity are registered. A three-well potential model with additive noise reproduces this dynamic. A regime of periodic response is observed when a very weak forcing is applied.