Abstract
In this paper, advanced wall-modeled large eddy simulation (LES) techniques are used to predict conjugate heat transfer processes in turbulent channel flow. Thereby, the thermal energy transfer process involves an interaction of conduction within a solid body and convection from the solid surface by fluid motion. The approaches comprise a two-layer RANS–LES approach (zonal LES), a hybrid RANS–LES representative, the so-called improved delayed detached eddy simulation method (IDDES) and a non-equilibrium wall function model (WFLES), respectively. The results obtained are evaluated in comparison with direct numerical simulation (DNS) data and wall-resolved LES including thermal cases of large Reynolds numbers where DNS data are not available in the literature. It turns out that zonal LES, IDDES and WFLES are able to predict heat and fluid flow statistics along with wall shear stresses and Nusselt numbers accurately and that are physically consistent. Furthermore, it is found that IDDES, WFLES and zonal LES exhibit significantly lower computational costs than wall-resolved LES. Since IDDES and especially zonal LES require considerable extra work to generate numerical grids, this study indicates in particular that WFLES offers a promising near-wall modeling strategy for LES of conjugated heat transfer problems. Finally, an entropy generation analysis using the various models showed that the viscous entropy production is zero inside the solid region, peaks at the solid–fluid interface and decreases rapidly with increasing wall distance within the fluid region. Except inside the solid region, where steep temperature gradients lead to high (thermal) entropy generation rates, a similar behavior is monitored for the entropy generation by heat transfer process.
Highlights
large eddy simulation (LES) require considerable extra work to generate numerical grids, this study indicates in particular that WFLES offers a promising near-wall modeling strategy for LES of conjugated heat transfer problems
A two-layer RANS–LES approach based on the Spalart–Allmaras model [31], an improved delayed detached eddy simulation method (IDDES) [27] and a non-equilibrium wall function model (WFLES) [7] were assessed in terms of prediction accuracy, physical consistency and computational cost
The comparative predictions of the conjugate heat transfer process due to conduction and convection as achieved by the different near-wall treatments for LES are divided into five parts
Summary
Advanced wall functions for the velocity (e.g., [7,15,16,17,18]) and for the temperature [7,18] were proposed in the literature that account for additional non-equilibrium effects like time rate change, convection or pressure gradients This allows accurate predictions of realistic heat and fluid flow applications with a reasonable computational cost, as was recently shown by the authors in [7]. A two-layer RANS–LES approach based on the Spalart–Allmaras model [31], an improved delayed detached eddy simulation method (IDDES) [27] and a non-equilibrium wall function model (WFLES) [7] were assessed in terms of prediction accuracy, physical consistency and computational cost.
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