LES of transient premixed flames using a dynamic flame surface density model

Transient premixed flames are significant in areas such as spark-ignition engines and gas explosions. However, physical understanding and accurate prediction remain challenging due to the fact that the flame typically transits from early quasi-laminar to fully turbulent, and the interactions with the surrounding solid structures often lead to the continuous stretching of the flame front. This study has considered the large eddy simulation (LES) techniques for the simulations of transient turbulent premixed flames. The LES technique has evolved as a powerful computational tool for the prediction of unsteady flame propagation. The difficulty of applying LES for turbulent premixed combustion is to account for the thin flame front using appropriate methods. This thesis considers a dynamic flame surface density (DFSD) model to close the filtered reaction rate. It automatically computes the model parameter based on the characteristics of the resolved flame front. The model is first validated in a one-dimensional laminar case to ensure the correct behaviours including the filtered flame thickness and laminar burning velocity with the absence of sub-grid turbulence. [Continues.]