Models for the large eddy simulation equations to describe multi-species mixing occuring at supercritical pressure

An existing database of direct numerical simulations (DNS) representing mixing of species under supercritical pressure (supercritical-ρ) conditions has been investigated for the purpose of understanding the modeling of the gradient of the filtered pressure, the divergence of the filtered heat flux, and the divergence of the filtered species mass flux, all in the context of large eddy simulation (LES). The analysis consists of two separate parts. The activities of all terms appearing in the LES equations are first evaluated, and the dominant terms for each of the transport equations are identified. These data are used to check whether the standard LES assumptions−i.e., that the three above quantities are equal to the gradient of the pressure and the divergences of the fluxes computed from the filtered flow field, respectively−that are routinely used for atmospheric-ρ flows, continue to be valid also in the realm of supercritical-ρ conditions. Having found that these assumptions do not hold under supercritical-ρ conditions, alternative modeling strategies for these terms are proposed, and their accuracy with respect to the standard LES assumptions is assessed