Affordable Explicitly Filtered Large-Eddy Simulation for Reacting Flows

This paper focuses on improving the grid convergence properties of large-eddy simulations. To isolate the impact of numerical filtering and the associated errors inherently present in implicitly filtered large-eddy simulation approaches, the authors have developed a novel explicit filtering approach suitable for any mesh topology and filter kernel. Simulations of a bluff-body stabilized, premixed flame configuration on a sequence of meshes are used to demonstrate this methodology. Grid convergence assessment is also performed for another approach, wherein the filter width at each computational cell is explicitly set. Comparisons show that solutions from prescribed-width implicitly filtered large-eddy simulation and explicitly filtered large-eddy simulation approaches exhibit good convergence for the mean quantities. The explicitly filtered large-eddy simulation results show clear convergence trends in the rms quantities, unlike the prescribed-width implicitly filtered large-eddy simulation approach and previously reported implicitly filtered large-eddy simulation results. While discrepancies exist in the level of agreement between the grid converged rms solutions with measured data, this could now be attributed to the errors in the physical models and boundary conditions. Importantly, the proposed explicitly filtered large-eddy simulation approach only reduces the computational efficiency by approximately 30% on the fine grid simulation, relative to the implicitly filtered large-eddy simulation approach.