Multi-point local temperature measurements inside the conducting plates in turbulent thermal convection

Abstract

An experimental study of local temperature statistics in turbulent thermal convection is presented. The emissions of plumes and plume clusters are detected by an array of thermistors embedded in the top and bottom plates of a 1 m diameter convection cell. We found that the product STST′ of the temperature skewness ST and the skewness of the temperature time derivative ST′ from the embedded thermistors may be used as a measure of the intensity of plume emissions and that STST′ exhibits a pattern that corresponds well to the orientation of the large-scale circulation in the convecting flow. This is despite the fact that the temperature distribution across the plates is highly uniform, as indicated by the mean temperature of the embedded thermistors. By comparing the spatial distributions of STST′ and of the RMS temperature σ, we further find that the maximum temperature fluctuations take place in regions dominated by plume mixing instead of regions of plume emission. It is also found that temperature fluctuations inside the conducting plates have the same statistical and scaling properties as those in the cell centre.