Wavenumber selection in Rayleigh-Benard convective structure

Abstract

The dislocation motion experiments we have performed, illustrate how the convective pattern,containing a single defect,findsa stationary state after a well defined evolution. This simple behaviour confirms that the transient evolution of textures at high Prandtl number may be understood as a phase of minimization of energy. The motions of dislocations also indicate that in our experiments a well defined preferred wavenumber does exist at each Rayleigh number, this selection criterion is the same as that offered by grain-boundaries. This agreement between selection criterions has motivated us to consider, that offered by the curvature in an axisyirmetric structure. This last experiment has shown the occurrence of an unexpected symmmetry-breaking of the structure, we conjecture that the large scale flows are at the origin of this symmetry-breaking. This is supported by our experimental observations. This symmetry-breaking destroys a part of the selection argument concerning axisym metric structures; however our experimental selection curves reported here, agree with the zero velocity dislocation curve, This agreement is astonishing since it does not seems to depend on the Prandtl number as expected.