A compressible-LEM turbulent combustion subgrid model for assessing gaseous explosion hazards

A turbulent combustion subgrid model, inspired by the Linear Eddy Model for Large Eddy Simulation (LEM-LES), is developed to study highly compressible and reactive flows involving very rapid transients in pressure and energy. The model is intended to be a one-dimensional treatment of a diffusion-reaction system within a multi-dimensional LES cell. The goal is to reduce the expense of solving a complete multi-dimensional problem through Direct Numerical Simulation (DNS) while preserving micro-scale hotspots and their physical effects on ignition. The current approach features a Lagrangian description of fluid particles on the subgrid for increased accuracy. Recently, the model approach has been verified for various fundamental 1-D test cases, including inert mixing, constant volume ignition, shock tube problems and laminar flame propagation. In the current study, the model is extended to treat turbulent methane-air flames in one-dimension. Also, a 1-D piston-driven laminar shock-flame interaction and its subsequent transition to detonation is modelled. Results confirm that both laminar and turbulent flame speeds are reproduced when compared against 1D computations of the Navier-Stokes equations (1D-NS) and experiments, respectively. Furthermore, the model offers a good prediction for detonation initiation in the presence of shock waves when compared to high and low-resolution 1D-NS simulations. Finally, the model is demonstrated to reproduce the correct detonation structures, velocities, and instability behaviour when compared to theory and the 1D-NS computations.