A.K. Gnanasundaram, T. Pestana, S. Hickel (2019) *11th International Symposium on Turbulence and Shear Flow Phenomena.* TSFP paper 2019-286

We investigate the underlying assumptions of Explicit Algebraic Subgrid-Scale Models (EASSMs) for Large- Eddy Simulations (LESs) through an a priori analysis using data from Direct Numerical Simulations (DNSs) of homogeneous isotropic and homogeneous rotating turbulence. We focus on the performance of three models: the dynamic Smagorinsky (DSM) and the standard and dynamic explicit algebraic models as in Marstorp et al. (2009), here refereed to as SEA and DEA.

By comparing correlation coefficients, we show that the subgrid scale (SGS) stress tensor is better captured by the EA models. Overall, the DEA leads to the best performance, which is evidenced by comparing how each model reproduces the probability density function (p.d.f.) of the SGS kinetic energy production. Next, we evaluate the approximations that are inherent to EA models such as the model for the pressure-strain correlation. We analyze the performance of three pressure-strain models commonly employed in the RANS framework: the LRR-QI, the LRR-IP, and the SSG models. Again, through correlation coefficients, and by splitting the pressure contributions into slow and rapid, we assess the relative performance of each model. Finally, we test the local equilibrium assumption of Marstorp et al. (2009), which considers a local balance between the SGS kinetic energy production and the dissipation. The probability density function shows that the ratio of SGS kinetic energy production to dissipation is distributed over a broad range of values and that the local equilibrium assumption can be only viewed as a mathematical simplification.