An experimental study of flow reversals in turbulent Rayleigh-B\'{e}nard convection in rectangular cells

We present an experimental study of reversals of the large-scale circulation (LSC) in turbulent Rayleigh-B\'{e}nard convection. The experiment was conducted in two rectangular cells with the heights and lengths being equal and fixed at 12.6 cm while the widths being 3.84 cm and 2.56 cm, corresponding to lateral aspect ratios $\Gamma$ being 0.3 and 0.2, respectively. It is found that reversals of the LSC occur more frequently in the $\Gamma=0.2$ cell than they do in the $\Gamma=0.3$ cell. The increased temperature fluctuations in the bulk indicates that there are more plumes going through the bulk flow due to the shear effects from the sidewall, which results in a less stable LSC thus more frequent flow reversals.