Flame Dynamics modelling using Artificial Thickened Models

Abstract

Thickened flame models are prolific in the literature and offer an effective method of resolving flame dynamics on coarse LES meshes. The current state of the art relies heavily on the use of efficiency functions to compensate for impaired wrinkling of the thickened flame. However in practice these functions can involve parameters that are difficult to determine, perform poorly outside of certain ranges or require \emph{a posteriori} analysis to evaluate performance. An alternative based on a generalised thickening is evaluated across a range of canonical configurations. The approach is demonstrated to perform well across a large range of thickening factors in capturing phenomena such as localised quenching and pinch off as well as generation of flame surface. Including good performance even in the case of large flame dynamics under acoustic forcing where the model has a clear advantage over DNS in achieving grid independence. Finally the approach is unified into an Large Eddy Simulation/Adaptive Mesh Refinement framework and applied to a turbulent Bunsen flame. The results show that even if the internal flame structure is poorly resolved on the original mesh, the global system behaviour is well predicted and compares favourably with other approaches.

Subgrid Turbulent Flux Models for Large Eddy Simulations of Diffusion Flames in Space Propulsion

“…Efficiency functions are common solution used to mitigate the effect of neglected physical features [30,33,34]. Nonetheless, the performance and reliability of these models remains an unsolved challenge, which has motivated intensive research activity during the last years [35,36,37]. Other remarkable approaches for LES modeling in turbulent combustion applications include the G-equation model [38,39] and the Flame Surface Density (FSD) models [40].…”

Subgrid Turbulent Flux Models for Large Eddy Simulations of Diffusion Flames in Space Propulsion

“…Efficiency functions are common solutions used to mitigate the effects of neglected physical features [30,33,34]. Nonetheless, the performance and reliability of these models remains an unsolved challenge, which has motivated intensive research activity during the last years [30,35,36]. Other remarkable approaches for LES modeling in turbulent combustion applications include the G-equation model [37,38] and the Flame Surface Density (FSD) models [39].…”