Quantitative Infrared Imaging of Impinging Turbulent Buoyant Diffusion Flames
Randall J. McDermott, Ashish Newale, Brent Rankin, Harshad Lalit, Jay P. Gore
Radiation from buoyant diffusion flames with and without impingement on a flat plate is studied using a unique quantitative comparison of measured and simulated images. The coupling between the stagnation boundary layer and upstream buoyant shear layer flows presents a model problem of practical significance for subgrid-scale treatment necessary for future fire simulations. Quantitative images of the radiation intensity from the flames are acquired using a calibrated high speed infrared camera. Numerical simulations are performed using Fire Dynamics Simulator (FDS) version 6. The simulated species concentrations, soot volume fractions, and temperatures are used in conjunction with a narrowband radiation model to calculate the radiation intensities by solving the radiative transfer nist-equation. The simulated radiation intensities are rendered in the form of images and compared quantitatively with the measured images. The measured and computed images of the radiation intensity reveal necking and bulging of the flame with a characteristic frequency of 7 ± 1 Hz which is in agreement with previous empirical correlations. The computations show overall good agreement with both the time-dependent and time-averaged measured images. The normalized RMS of the radiation intensities show a decreased magnitude of the oscillations upstream of the plate. The effects of the stagnation point boundary layer on the upstream buoyant shear flow include much smaller size of the roll-up vortices with significant asymmetry in the computations in comparison to the experiments. The computed infrared images of the boundary layer are occasionally much thicker than the measured infrared images. These results point to improvements in the sub-grid scale models to account for the transitional organized structures.
August 3-8, 2014
San Francisco, CA
Thirty-Fifth International Symposium on Combustion