Assessment of wall-modeling approaches for large eddy simulations of natural convection

Simulations of turbulent natural convection at high Rayleigh numbers are computationally very expensive due to grid-resolution requirements, especially in the near-boundary regions where hydrodynamic and thermal boundary layers are developed. For this reason, it is common to resort to Wall-Modeled Large Eddy Simulations (WMLES), according to which the turbulent scales in the inner layers are modeled and not resolved. This allows to reduce the number of grid points in the near-boundary regions, which offers significant computational savings. In this talk, we present WMLES of Rayleigh-Bénard convection at different Rayleigh numbers that involve modeling both the hydrodynamic and thermal boundary-layer structures. In particular, different wall-modeling approaches for the temperature field are discussed and their predictions are compared. Additionally, we address the issue of the modeling of the thermal boundary layer at free-slip boundaries such as, for example, the free surface of a liquid. To this end, we examine different approaches and assess their efficacy via comparisons of their predictions with those of wall-resolved simulations of turbulent natural convection in an open cavity.