Constrained Large Eddy Simulation for incompressible wall-bounded turbulence with passive scalar field

Transfer of passive scalars, such as heat and mass, by turbulence is a crucial process in many natural and engineering applications, and accurately modeling of such processes is of great importance. In this work we present a new method of large-eddy simulation (LES) for wall-bounded turbulence with passive scalar. Specifically, we extend the so-called constrained-LES (CLES) of wall-bounded turbulence to the scalar turbulence. CLES was first developed by Chen et al. (2012) to successfully resolve the mismatch problem of mean velocity profiles in detached-eddy simulations. Following the same methodology, here the scalar field is solved by using LES over the whole domain. A Reynolds averaged Navier–Stokes (RANS)-type of turbulent scalar flux is imposed onto the subgrid stress only within an inner layer adjacent to the wall boundary. Specifically, we utilize an eddy diffusivity model for the RANS turbulent scalar flux. With this constrain, the mean scalar profile of the inner layer can be accurately obtained while the small-scale structures in scalar field are still retained. The method is validated by the comparison with DNS of channel turbulence with passive scalar, and the results suggest that the current method can successfully resolve the log-layer mismatch in mean scalar profiles. The method can accurately generate the mean scalar profile, scalar fluctuation profile, turbulence scalar flux, and global Nusselt number for a wide range of Reynolds and Prandtl numbers in channel turbulence.