Influence of cavity and ramp layout on combustion performance in a strut-based scramjet combustor

The computational analysis focuses on the flow performance of a wall-mounted cavity and ramp within DLR scramjet model operating in a reacting flow environment. The analysis encompasses a base setup aligned with DLR experiments, along with suggested configurations featuring different lower wall cavity depth and a fixed upper wall ramp. The 2-D Reynolds-Averaged Navier-Stokes approach (RANS) combined with Shear Stress Transport (SST) k-ω turbulence model, which incorporates single-step reaction chemistry, is utilized in steady-flow simulations. Subsequently, the unsteady-flow computations are completed using the Delayed Detached Eddy Simulation (DDES) with the SST k-ω turbulence model as a continuation of RANS analysis to compute and observe the coherent structures by using data driven methods. To examine shock structures and their associations with shear layer mixing characteristics, the cavity and ramp are positioned downstream of the strut. Inclusion of the cavity and ramp increase the number of shock waves in the flow substantially. Accordingly, complete combustion occur earlier than in the baseline model which is accompanied by a subtle increase in total pressure loss. Due to intense interactions between shock waves and shear layers, combustion zone widens laterally as the cavity displaces the shock train downstream of the strut injector. DDES results are processed to observe the dynamics and the coherent structures employing Dynamic Mode Decomposition (DMD) and Spectral Proper Orthogonal Decomposition (SPOD) methods. Both analysis show that the recirculation zone proceeds into the core engine with the progressive deepening of the cavity leading to a consequential stationary combustion.