Local Energy Dissipation Rate Balances Local Heat Flux in the Center of Turbulent Thermal Convection

The local kinetic energy dissipation rate epsilon(u,c) in Rayleigh-Benard convection cell was measured experimentally using the particle tracking velocimetry method, with varying Rayleigh number Ra, Prandtl number Pr, and cell height H. It is found that epsilon(u,c)/(kappa(3)H(-4)) = 1.05 x 10(-4)Ra(1.55 +/- 0.02)Pr(1.15 +/- 0.38). The Ra and H dependencies of the measured results are found to be consistent with the assumption made for the bulk energy dissipation rate epsilon(u,bulk) in the Grossmann-Lohse model. A remarkable finding of the study is that epsilon(u,c) balances the directly measured local Nusselt number Nu(c) in the cell center, not only scalingwise but also in magnitude.