HIGH-FIDELITY NUMERICAL SIMULATIONS OF INLET / ISOLATOR / COMBUSTOR INTERACTIONS

The proposed work leverages a suite of high-fidelity modeling tools (wall-resolved largeeddy simulations, hybrid large-eddy-simulation / Reynolds-averaged Navier-Stokes techniques, and 'embedded direct numerical simulation' strategies for enhanced resolution of turbulent flame structures) to predict dynamic modes of scramjet engine operation. The initial focus of this computational effort is an axisymmetric inlet / isolator / combustor configuration being tested at the University of Illinois's ACT-II arc-heated combustion facility. Planar, time-resolved OH-PLIF and OH* chemiluminescence imagery have been used to provide insights into flame propagation characteristics during stable scram and ram-mode operation as well as during mode transition, but a complete picture of the reactive flow physics within the device has yet to emerge. Results from the computational simulations will help answer key questions, including the role of the cavity in enhancing combustion without apparently acting as a flame-holder, the physical pathways that lead to thermal throat formation and propagation, mechanisms of flame stabilization during mode transition, and the origins of self-sustained oscillations of the isolator shock-train / flame system when in ramjet mode. The work will evolve in close collaboration with the University of Illinois team – out-year tasks will include predictive and postdictive simulations of non-axisymmetric isolator / combustor geometries to be tested in ACT-II along with simulations that support the design and testing of inlet / isolator / combustor configurations in the University of Queensland's X3R shock tunnel.