Devaud, CecileAbdalhamid, Ahmed Mohamed Khairy Abdalnaby2024-12-122024-12-122024-12-122024-12-10https://hdl.handle.net/10012/21243Conditional Source-term Estimation (CSE) is a turbulent combustion model that relies on conditional averages of species mass fractions to provide closure for the mean chemical source terms. The model has the ability to account for detailed chemical kinetics while remaining computationally affordable for engineering cases. CSE has been successfully applied previously to simulate flames of different regimes and configurations. The current work aims at extending the CSE framework to model turbulent buoyant diffusion flames for the first time. Large Eddy Simulation (LES) is used to solve transport equations of mass, momentum, species and enthalpy. Chemistry is pretabulated prior to the simulations. The LES FireFOAM solver is coupled with CSE approach. The new solver is first tested against University of Maryland methane line fire using different implementations for radiation modelling, all relying on the optically thin assumption. The results are validated against experimental measurements at different locations as well as previously published predictions of the same case using different combustion models. The predicted temperatures are in good agreement with the experimental data, except very close to the fuel inlet. The predicted flame height closely matches the experimental value. The predictions are consistent with previously published results as well. Next, the inclusion of radiation absorption is considered by solving the radiative transfer equation (RTE), avoiding the optically thin approximation for the first time with CSE. Moreover, the weighted sum of grey gases (WSGG) approach is employed to estimate the absorption coefficients. The new framework is applied to the simulation of two medium and large scale methanol pool fires. The medium scale case is investigated using two angular meshes and compared to the optically thin results. The case that solves the RTE with fine angular mesh shows improved predictions. The radiative flux results show that the predictions align better with the measurements with the finer angular mesh outside the flame region. However, the results from both angular meshes are in agreement within the flame. For the large scale case, the time-averaged temperature predictions are in good agreement with the experimental data, except on the centerline downstream of the flame region where the results are overpredicted. Finally, the newly developed CSE framework is extended to include soot modelling by coupling with two of the most widely used soot models in fire analysis. The new approach is used to simulate the ethanol pool fire case, providing acceptable predictions of soot and species mole fractions. In conclusion, this study proves the capability of CSE in accurately simulating turbulent buoyant diffusion flames. Future work may address more complex fuels, cases of extinction with doubly-CSE, suppression by water mist, and more detailed soot models.encombustionturbulentCSELESRTEWSGGsootDoctoral Thesis