Impact of grid refinement on turbulent combustion and combustion noise modeling with large eddy simulation

Abstract

For Large Eddy Simulation (LES) of turbulent combustion, as the turbulent flow as well as the thin flame front are directly filtered by the cut-off scale, resolution of the computational grid plays a very important role in this case and represents always a quality determining factor. In addition, the fluctuation of heat release is found to be the main source for noise generation from turbulent combustion, which is attributed to the interaction of the turbulent flow and the combustion reaction. As the flame is thickened or filtered respectively by the computational grid, it becomes less sensitive to fluctuations of the flow as well, so that the emitted noise from the flame due to unsteady heat release is affected by the grid resolution in LES combustion modeling as well. The current work represents an investigation with respect to these aspects. For this purpose, LES and DNS simulations for a realistic jet flame at moderately turbulent condition have been carried out. The LES calculations have been performed on computational grids with different resolutions (0.4/3.2/10.7 million cells) on the HP XC4000 cluster of the Steinbuch Centre for Computing (SCC) at the KIT. In order to assess predictability of the LES methodology, a three-dimensional DNS simulation on a grid with 54 million cells has been carried out on the Cray XE6 (HERMIT) of the High Performance Computing Center Stuttgart (HLRS). The comparison of the LES solution with experimental and DNS data allows an evaluation of the influence of the grid refinement to a great extent.