Explicitly filtered LES of two-phase flow with evaporating droplets

摘要

To investigate whether predictions from conventional Large Eddy Simulation (LES), which are known to be grid-spacing and spatial discretization-order dependent, can be rendered grid-spacing and discretization-order independent, we have reformulated LES by explicitly filtering the non-linear terms in the governing equations.1 The encouraging results we obtained1 for compressible single-phase flow motivated our present study in the context of evaporating two-phase flow. Thus, we created a database through Direct Numerical Simulation (DNS) to serve, when filtered, as a template for comparisons with both conventional LES and explicitly-filtered LES (EFLES). Conventional LES is conducted with the Smagorinsky model for the gas phase, and EFLES is also performed with Smagorinsky model; the drop-field SGS model is the same in all these simulations. The results from all these simulations are compared to those from DNS and from the filtered DNS (FDNS). Similar to the single-phase flow findings, the conventional LES method yields solutions which are both grid-spacing and spatial discretization-order dependent. The EFLES solutions are found to be grid-spacing independent for sufficiently large filter-width to grid-spacing ratio, although for the highest discretization order this ratio is larger in the two-phase flow compared to the single-phase flow. For a sufficiently fine grid, the results are also discretization-order independent.