Direct and Large Eddy Simulation of three-dimensional non-Boussinesq gravity currents with a high order DG method

24/2018

Direct and Large Eddy Simulation of three-dimensional non-Boussinesq gravity currents with a high order DG method

Friday 13th April 2018

Bassi, C.; Abbà, A.; Bonaventura,L.; Valdettaro,L.

We present results of three-dimensional Direct Numerical Simulations (DNS) and Large Eddy Simulations (LES) of turbulent gravity currents with a Discontinuous Galerkin (DG) Finite Elements method. In particular, we consider the three-dimensional lock-exchange test case as a typical benchmark for gravity currents. Since, to the best of our knowledge, non-Boussinesq threedimensional reference DNS are not available in the literature for this test case, we first perform a DNS experiment. The threedimensional DNS allows to correctly capture the loss of coherence of the three-dimensional turbulent structures, providing an accurate description of the turbulent phenomena taking place in gravity currents. The three-dimensional DNS is then employed to assess the performance of di?erent LES models. In particular, we have considered the Smagorinsky model, the isotropic dynamic model and an anisotropic dynamic model. The LES results highlight the excessively dissipative nature of the Smagorinsky model with respect to the dynamic models and the fact that the anisotropic dynamic model performs slightly better with respect to its isotropic counterpart.