Inhibition of phase turbulence close to onset of convection by permeable lateral boundary condition for the mean flow

Abstract : We show that the mechanisms which govern the onset of time dependence in usual Rayleigh-Bénard convection at low Prandtl number may be inhibited by a suitable choice of the lateral boundary condition for the sole mean flow. We first build a boundary condition which behaves like a rigid one for the roll flow and like a permeable one for the mean flow. We then observe that phase turbulence is inhibited close to the onset of convection. We understand this effect by solving the mean-flow field from the Cross-Newell equations. Our experimental result together with its interpretation demonstrates indirectly the existence of mean flows and enlightens the ways by which mean flows destabilize patterns.