Impact of Computational Domain and Cell Type on Large Eddy Simulations in OpenFOAM for a Turbulent Partially Premixed Flame

Large eddy simulations (LES) are becoming state-of-art for industrial combustion applications due to its capability to better capture fluid mixing and flame front by resolving large-scale turbulent eddies. However, this increased sensitivity to the physics can become more demanding on the numerical and meshing methods and boundary condition requirements. This paper highlights some challenges in performing LES of a canonical turbulent partially premixed flame (Sandia flame D) in open-source CFD platform OpenFOAM. Both RANS and LES approaches were evaluated, and it was found that time-averaged flow and combustion properties were captured by RANS with reasonable ease and accuracy. However, LES was not able to capture the flame eddies and turbulent diffusion at the first attempt. LES results were found quite sensitive to the computational mesh and modelling methods. As the flow unsteadiness is captured in LES, the turbulence and acoustic boundary conditions also become important. Explorations on all these aspects are made, and finally, conclusion is made on the importance of using structured mesh over unstructured mesh and avoidance of two-dimensional axisymmetric domains in the OpenFOAM CFD solver, specifically in the LES context.