The influence of large-scale flow on heat transport in turbulent thermal convection is experimentally investigated. Large-scale flow couples the upper and lower thermal boundary layers. This coupling produces a slow coherent oscillation of the temperature field and strongly influences the spatial distribution of temperature fluctuations. Moreover, when the large-scale flow is either suppressed or strongly modified no significant variation of the heat transport across the cell is observed.

• Received 29 April 1996

DOI:https://doi.org/10.1103/PhysRevE.54.R5901