Large-eddy simulations of bluff body stabilized flames

Abstract

The objective of this paper is to extend a previously developed large-eddy simulation (LES) model, originally developed for anisochoric high-Reynolds-(Re-) number flows, to include chemically reacting flows as well. The LES model, developed from a physical model founded on modern continuum-mechanical mixture theories, includes a complete treatment of the subgrid stresses and fluxes. Different multistep global reaction schemes have been adopted along with a combustion model that considers the influence of subgrid effects on the effective chemical reaction rates. In order to study the predictive capabilities of this LES model, numerical simulations of the flow behind a two-dimensional generic bluff body in a straight channel have been undertaken, and results are compared with measurements from experimental investigations. In the simulations of reacting flow situations, the fuel was propane, and premixed conditions were enforced. The measurements were done with nonintrusive methods such as the 2λ-CARS technique, giving temperature probability density functions (pdfs) and profiles, as well as traditional gas analysis, giving temperature profiles. Comparison of simulated and measured temperature pdfs and profiles indicates that the LES technique works well for unsteady premixed flows, and it mimics most of the significant flow features, including typical unsteady flow structures and the flame-front dynamics.