Statistics of the locally averaged thermal dissipation rate in turbulent Rayleigh-Benard convection

From the measured thermal dissipation rate in turbulent Rayleigh-Benard convection in a cylindrical cell, we construct a locally averaged thermal dissipation rate f by averaging over a time interval . We study how the statistical moments <(f)p > depend on at various locations along the vertical axis of the convection cell. We find that <(f)p > exhibits good scaling in , of about a decade long, with scaling exponents (p) for p = 1-6. For Rayleigh number (Ra) around 8x109, the scaling range is 1.4-21 s at the cell center and 4-21 s at the bottom plate. The dissipative and turnover times are about 0.8 s and 35 s respectively, while the timescale corresponding to the local Bolgiano scale is estimated to be about 31 s at the cell center and 3.5 s at the bottom plate. On the basis of several assumptions, we derive theoretical predictions for (p) at the different locations. The measured values of (p) are presented and shown to be in good agreement with our theoretical predictions.