Instabilités hydro-thermiques dans un anneau cylindrique vertical soumis à un fort gradient radial de température

We investigate experimentally the influence of a radial temperature gradient in a vertical annulus. The geometrical parameters are fixed with aspect ratio and radius ratio respectively equal to 114 and 0.8. After imposing a Grashof number Gr, related to the radial temperature gradient, the convection cell is destabilized by inertial forces due to the increasing of the rotation of the inner cylinder. Above a critical value of the Taylor number Ta, related to the velocity of the inner cylinder, a spiral pattern occurs giving rise to a finite extent propagating pattern. For Gr 965, the spiral pattern is modulated. It appears around mid-height and nearly fills the system at threshold.