Comparison of Reacting DDES and LES CFD Simulation Methodologies for a Dual Inlet Ramjet Engine Combustor

The design of a dual inlet dump ramjet combustor is critical in the development of propulsion systems. Parameters such as pressure drop, pressure fluctuations, and combustion efficiency must be evaluated across various flight regimes. In this study, Large Eddy Simulation (LES) and Delayed Detached Eddy Simulation (DDES) techniques, coupled with the Steady Laminar Flamelet combustion model, are used to model a generic ramjet combustor. Grid convergence was ensured through the application of the Richardson extrapolation method, and the grid quality was evaluated using the M-index. A close agreement between both LES and DDES approaches and experimental data was observed, confirming their accuracy in simulating the complex flow behavior of the combustor. The present research demonstrates that the Steady Laminar Flamelet model is capable of predicting flow structures in a ramjet combustor under reacting conditions. Within LES simulations, the prediction of turbulent kinetic energy within the near-wall region was enhanced, resulting in faster mixing and an overestimation of combustion efficiency. Even closer agreement with experimental data was achieved in DDES predictions, highlighting the effectiveness of employing eddy simulation with near-wall modeling when wall resolution is unfeasible. This approach not only demonstrates better agreement between DDES predictions and experimental data but also showcases its efficiency in reducing the need for excessively refined meshes in the study of dump-type low subsonic combustors.