Spectral Characterization of Overdriven Irregular Detonations*

Rotating Detonation Engines (RDEs) have garnered great interest in recent years due to promising performance efficiencies stemming from compact detonation heat-release rather than deflagration. However, gaps in understanding underlying turbulent irregular detonation processes and the lack of accurate CFD predictions has withheld prototypes from achieving the targeted efficiencies. To inform the development of accurate sub-grid scale (SGS) models for turbulent irregular detonation, we propose a novel spectral description of turbulent irregular detonation, focusing on cell-structure and chemistry spectra. We attempt to quantify and better explain the broad-range of cell-sizes and the influence of the underlying chemical processes from high-quality numerical data generated from Adaptive Mesh Refinement (AMR)-based DNS-like simulations. An overdriven detonation wave composed of a stoichiometric methane-oxygen mixture is studied for which numerical soot foils are generated to obtain cell-size spectrum. A conservative chemical explosive mode analysis (CCEMA) is also conducted to generate chemistry mode spectra which exhibit similar trends indicating tight coupling.