Turbulent convection with "disconnected” top and bottom boundary layers

We have done an experimental study of turbulent thermal convection in water using a cell with a baffle placed at its mid-height, over a range of Ra that spans from 2 × 10 8 to 2 × 10 10 . It was found that in this case the large-scale circulation is not able to advect heat between the top and bottom plates and heat has to be carried across the baffle mainly by thermal plumes. Furthermore, the measured Nu still scales with Ra with an exponent consistent with "2/7" for Ra > 1 × 10 9 . For Ra below this value, the scaling of Nu with Ra is more consistent with an exponent of "1/3". The measured temperature PDFs also show signatures of "soft" and "hard" turbulence below and above Ra ≃ 1 × 10 9 , respectively.