Comparison of thermal scaling properties between turbulent pipe and channel flows via DNS

A systematic comparison of thermal scaling properties of pipe and channel flows is presented. DNS data are used to compute thermal statistics for friction Reynolds numbers of 180 and 395 and Prandtl numbers ranging between 0.025 and 7. A distinct four layer regime for the thermal field is clearly identified in both channel and pipe flows. The analysis reveals that the balance breaking and exchange of leading order terms in the mean energy equation that occurs across an intermediate layer is similar to the exchange of terms in the mean momentum equation. The present analysis suggests that, at high Peclet numbers in the four layer regime, the scaling characteristics of the temperature field become increasingly similar to those of the momentum field at high Reynolds number. The intermediate normalisation found by adopting the theory used for the momentum field provides a convincing scaling for the mean temperature and turbulent heat flux profiles for both pipe and channel flows. In contrast to velocity field statistics, the inner normalized mean temperature and heat flux profiles show significant discrepancies between pipe and channel flows. (C) 2014 Elsevier Masson SAS. All rights reserved.