Large-Eddy Simulation and experiments on non-premixed highly turbulent opposed jet flows

An experimental and computational study is presented on highly turbulent non-premixed counterflows under both isothermal and reactive conditions. Experimentally, Hot Wire Anemometry (HWA), two-dimensional Particle Image Velocimetry (PIV) and OH Planar Laser Induced Fluorescence (PLIF) were applied. Computationally, Large-Eddy Simulations (LES) with a steady flamelet model were used to simulate the flow inside the nozzles and in the opposed flow region, using three different grid resolutions between 1.0 and 0.2 mm (0.5-70 million cells). The combined experimental and computational approach enabled the cross-validation of the simulation, and provided additional insight into the flow field. Both isothermal and burning conditions were examined with turbulent Reynolds numbers reaching a value of 900, demonstrating the system capability of reaching conditions of relevance to practical systems. Importantly, the simplicity of a compact, bench-top experiment is retained. The extension of the computational domain to a region within the nozzles with no optical access reveals the mechanism by which a specially designed turbulence generating plate (TGP) and burner housing yield turbulence intensities well exceeding 20%. The simulated and measured data were found to be in good agreement for first and second velocity moments, for the axial velocity autocorrelation function and for the normalised mean OH fluorescence. Similarity of OH-based flame morphology between experiments and computations also confirms that the LES successfully captures key features of the flow. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.