Wall-resolved large eddy simulation of turbulent mixed-convection heat transfer along a heated vertical flat plate

•Until the present study, none of the prior computations have been able to show detailed near-wall agreement with the experimental data for the streamwise turbulent heatflux.•Despite an increase in the wall shear stress as the freestream flow was increased, the boundary layer thickness diminished due the suppression of the large eddies in the outer layer.•The decrease in wall heat transfer was a consequence of the suppression of the outer layer large turbulence length scales.•The production of turbulent kinetic energy dominated by sweeps in wall bounded forced convection turbulence was absent in the near-wall region of the turbulent mixed convection boundary layer. The present study aims to assess the predictive capabilities of wall-resolved large eddy simulation (LES) in computing the fluid flow and heat transfer characteristics in a mixed-convection turbulent boundary layer that developed along a large flat plate vertically mounted in air. The maximum Rayleigh number was approximately 3×1011, which resulted in fully developed turbulence conditions. To enhance the accuracy, computational efficiency, and numerical stability, the LES solved the low-Mach number compressible flow governing equations, which included fluctuating density effects and pressure-density decoupling. For the subgrid scale (SGS) closure, a locally dynamic Smagorinsky SGS model was implemented into the LES solver to enable the backscatter phenomenon intrinsic to transitioning boundary layer flows. The LES illustrated exceptional agreement with the statistics profiles in the boundary layer obtained with the experiments of previous studies, which showed sensitivity to freestream conditions. In particular, the LES correctly predicted the turbulent heat flux in the streamwise direction near the heated surface. Furthermore, the LES captured the rapid changes in spectra of fluctuating temperature and velocities due to the delay of transition with increasing freestream velocity.