Figure 8.

(a) Analytical velocity profiles $u\left(y,t\right)$ at $t$ = 100 s (O), 1000 s (◁), and 2000 s (☐) during the experimental run. The evolution of $u\left(y,t\right)$ during the recording of $N_i$ = 20 consecutive images is illustrated. At each time $t$, the figure reports: the velocity profile captured by the first image of the group; the velocity profile captured by the last image of the group; the average velocity profile (solid black lines) that the image resulting from the average of the $N_i$ images would represent. (b) Relative variation of the velocity profile with respect to the average velocity profile at $t$ = 100 s (O), 1000 s (◁), and 2000 s (☐).