Neutron Scattering Study of Transitions to Convection and Turbulence in Nematic Para-Azoxyanisole

The critical temperature gradients for the onset of convection and turbulence were measured in nematic para-azoxyanisole. The transition to turbulence was found to occur through two successive instabilities. The first of these clearly signals the entrance to a periodic-motion regime, and the second, although less clearly, to a regime with nonperiodic, time-dependent motion. A typical phase-transition behavior was observed at the transitions to turbulence.