We report an experimental evidence of a global bifurcation on a highly
turbulent von Karman flow. The mean flow presents multiple solutions: the
canonical symmetric solution becomes marginally unstable towards a flow which
breaks the basic symmetry of the driving apparatus even at very large Reynolds
number. The global bifurcation between these states is highly subcritical and
the system thus keeps a memory of its history. The transition recalls
low-dimension dynamical systems transitions and exhibits a very peculiar
statistics. We discuss the role of turbulence in two ways: the multiplicity of
hydrodynamical solutions and the effect of fluctuations on the nature of
transitions.Comment: submitted to Physical Review Letters 19 May 2004, accepted 10
September 200
