Subgrid-scale modeling considerations for near-wall turbulent flow and heat transfer at supercritical pressure: a priori study

Challenges arise in large eddy simulation (LES) of near-wall turbulent flow and heat transfer at supercritical pressure (SCP) due to the drastic and nonlinear variation of thermophysical properties. There remains uncertainty regarding the validity of extending the LES framework developed for low-pressure, ideal-gas flows to simulations of SCP fluid flows. To address this issue, we revisit the LES framework and assumptions for near-wall turbulent boundary layers at supercritical pressure. Direct numerical simulations are conducted for turbulent channel flow of CO2 at 8MPa, with varying upper-tolower temperature differences (20K, 100K, and 150K). A priori assessment of subgrid scale (SGS) terms at different filter widths in LES is conducted using DNS results, accompanied by error analysis, order of magnitude analysis. The results show that SGS thermophysical properties, which are commonly overlooked in LES of ideal gases or fluids with minor property variation flows, become significant in magnitude compared to other terms in the governing equations. There are notable discrepancies in SGS thermophysical properties computed using different primary scalars. Furthermore, correlation analysis is conducted to derive potential parameters for SGS thermophysical modeling.