Modeling of unsteady combustion utilizing continuum mechanical mixture theories and large eddy simulations

摘要

This thesis considers the development of a consistent set of Large Eddy Simulation (LES) models for unsteady combustion. The theoretical background for the simulation models is modern continuum mechanical mixture theories, which provide the necessary framework for a hierarchical structure of theoretical models. Furthermore, this theoretical framework includes multi-temperature mixtures as well as multi-phase flows. Instead of increasing the capability of the theoretical model to encompass such processes, the theoretical model contains these elements from the beginning. Consequently, the model can systematically be reduced to give models for a large number of processes or systems. This is more attractive compared to the traditional approach, due to the generality and the high degree of adaptability. Since the aim is to study unsteady combustion processes, a simulation model having high spatial and temporal resolution is needed. Due to the well known resolution problem, some degree of phenomenology must inevitably be included in the physical model to replace some processes occurring at a microscopic level. This leads us to the Large Eddy Simulation methodology. A LES model has therefore been developed to encompass the theoretical model above. The LES model is cast into a numerical simulation model by a finite volume discretization and high-order interpolation approximations for the fluxes. In order to investigate the predictive capabilities of this LES model, numerical simulations have been performed on several configurations corresponding to test rigs or objects for which experimental data is available. Comparison indicate that, in all cases investigated, the LES model gives reliably predictions. 187 refs, 4 figs