Etude numerique de conditions aux limites en situation de combustion turbulente non premelangee

This work is a numerical study on the turbulent non-premixed flame HM1 of Sydney's University. The main objective of this thesis is to analyze the predictions of the vectorial and scalar quantities as a function of various boundary conditions applied to the annular flow field. The cases analyzed here are compared with experimental results Dally et al. (1998a). To fulfill the objectives of this thesis, the present document is divided in three main sections. First, a grid sensitivity analysis is performed on the two main categories of grid (for first and second order turbulence model) in order to show the effect of the physical discretization on each of the turbulent modeling approach. The second part of this work consists on a study of the turbulence models, already implemented on ANSYS CFX, that can be used for simulating both inert and reacting flows. Thus, the inert flow of Dally et al. (1998a) is simulated using first and second order closure models modeling approach in order to choose the best model to be used for the reacting case. Also, a first sensitivity case study of the annular boundaries conditions is performed on the non reacting flow. The main and last topic of this thesis features the simulation of the HM1 turbulent flame of Dally et al. (1998a). For this reacting case, the modeling of combustion and turbulence is respectively done by using the flamelet regime hypothesis and the EARSM model. The first annular boundary condition analysis is performed by using the experimental profile of velocities and turbulent energy. Then, to try enhancing the quality of the vectorial and scalar quantities prediction, the profils of those quantities are imposed to follow a mean uniform distribution. The main difference of this approach is that those uniform profils are applied to grids featuring different annular channel development length. The goal of this approach is to demonstrate which annular boundary condition would be the most effective to correctly predicts the HM1 flame quantities. For this study, the vector fields of the reacting case is firstly depicted in order to characterize the turbulent structure of the flow. Then the scalars quantities such as mixture fraction, temperatures and concentration of chemical species are also analyzed as a function of their respective annulus boundaries conditions. The simulation showed that the usage of the EARSM model in addition to the experimental annular boundary conditions helped significantly enhancing the predictions of the non-reacting flow, particularly for the measured stations far away from the bluff-body face.* While simulating the reacting flow, using the experimental boundary conditions had the contrary effect and decrease the quality of the predictions and the uniform proms cases were the ones that give better results. Overall, the predictions of temperatures are generally in good agreement with the experimental results for all measured stations. On the other hand, the chemical species concentrations do not follow the same trend and the validity of the predictions are restricted to a region of 45 mm from the burner's face.;Keywords: Flamelet, Bluff-body, Turbulence, Non-premixed combustion...