Figure 1

Left: shadowgraph images for $R=5.6\times {10}^8$. The elongated black stripes are hot plumes just above the bottom plate. Right: temporal correlation functions of two images separated in time by 1.22 s. Only the part inside the white squares ($31\times 31{\mathrm{mm}}^2$) in the images was used. Black dots at the centers of the correlation functions mark their origin.Reuse & Permissions

Figure 2

Temporal evolution of the angle $\Theta$ of the horizontal velocity component of the plumes close to the bottom plate. As for Fig. 1, $R=5.6\times {10}^8$.Reuse & Permissions

Figure 3

Angular frequency $\omega$ (in units of $L^2/\kappa$) of the angle $\Theta$ of the horizontal plume motion above the bottom plate for the slightly tilted (open circles) and the untilted (closed circles) apparatus. Solid (dashed) line: fit of a power law to the data of Ref. 9 (Ref. 12).Reuse & Permissions

Figure 4

Autocorrelation of $\Theta$ for $R=8.37\times {10}^8$. Lower panel: an expanded small time interval of the upper one.Reuse & Permissions

Figure 5

Cross correlation between the direction of the hot and cold plumes for $R=9.77\times {10}^8$.Reuse & Permissions

Figure 6

Schematic summary of a snapshot of the plume movement. The small angle at the bottom labeled $2°$ indicates the tilt of the apparatus relative to gravity. The curved double-headed nearly horizontal lines near the top and bottom indicate the amplitude of oscillation of the angle $\Theta$. The arrows through the top and bottom plane are an example of the direction of flow at an angle $\Theta$ at the top and $-\Theta$ at the bottom at a given time. Although not directly evident from our measurements, we assume that the instantaneous direction of flow near the sidewall is given by connecting the head of the top (bottom) arrow with the tail of the bottom (top) arrow.Reuse & Permissions