Numerical analysis of a turbulent reacting flame using comprehensive modeling approaches: RANS, LES and hybrid RANS-LES

A thorough analysis and comparison among the Reynolds-averaged Navier-Stokes (RANS), large eddy simulation (LES) and dynamic hybrid RANS-LES approaches have been conducted in simulations of a turbulent diffusion flame. In this work, a hydrogen-carbon monoxide flame is investigated with the laminar flamelet model associated with the reduced chemical mechanism to simulate the turbulence-chemistry interactions. Reasonable agreement with published experimental results has been determined from the time-averaged simulation results in terms of mixture fraction, temperature and species. It was found that RANS was sufficient to provide accurate predictions of the time-averaged flame characteristics with much less computational costs. However, the predicted results from the LES and hybrid RANS-LES have shown substantial improvements in predicting the instantaneous flame propagation and detailed turbulent vortex structures. Both time-averaged results even showed better predictions in the flame shear layer, indicating the intense mixing field was not well captured in the RANS method. This work demonstrated the sound performance of LES and the newly developed hybrid RANS-LES in predicting turbulent diffusion flame.