Large Eddy Simulation (LES) has become an increasingly useful tool for the prediction of turbulentudreactive flows with the increasing availability of cheaper and faster computing power.udIn the context of premixed combustion, LES encounters the challenge of resolving the flameudthickness, which is normally smaller than the filter width used in typical engineering applications.udThis thesis considers the Flame Surface Density (FSD) approach to provide closureudto the filtered LES reaction rate. The FSD can either be modelled algebraically (FSDA) oruddetermined through a transport equation (FSDT) and both approaches are investigated in theudLES of three different test cases. The first case explores the response of different FSDA modelsudtowards changes in turbulence levels, and compares the instantaneous flame structures andudreaction rates predicted by FSDA and FSDT methods. The remaining cases examine the LESudof two turbulent premixed burners. A relatively large range of FSDA models are tested underudthe same operating conditions for the first time, and the LES-FSDT equation is applied toudpremixed flames that involve a higher level of geometric complexity than earlier work. Generally,udthe results show that the performance of some FSDA models are inconsistent betweenudthe two premixed burners, suggesting that the models may operate optimally under differentudturbulent conditions. By contrast, the consistently good agreement of the FSDT results withudexperiments suggests that the method has much potential in the LES modelling of turbulentudpremixed flames. However, the improved FSDT predictions were dependent on the value ofudthe model constant within the sub-grid curvature model, and the value yielded an additionaluddependency on filter width. For these reasons as well as for the higher computational expense,udthe effective use of FSDT requires further development, while the application of the FSDAudmodels remains a viable alternative to the FSDT approach.
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