“…Recorded lines at regular intervals (0.2 s) are stacked together to make space-time diagrams I (z,t) along a line of flow patterns. The duration of the data recording is T rec over a length L rec ; in most of the experiments, T rec = 18 618λ and L rec = 41 d. In order to characterize quantitatively the hydrodynamic fields in the neighborhood of the defects, we have used the particle image velocimetry (PIV) to measure velocity fields in meridional cross section, i.e., in the (r,z) plane [41,42]. These measurements were performed in a vertical Tayor-Couette cell with a = 4 cm and b = 5 cm and L = 45 cm designed especially for PIV; it is immersed in a large rectangular tank with a temperature fixed at T = 22 • C ± 0.2 • C.…”