Image Analysis of Hydroxyl-Radical Planar Laser-Induced Fluorescence in Turbulent Supersonic Combustion

Flow visualization and statistical analysis of a supersonic, turbulent reacting flow from nonintrusive hydroxyl radical planar laser-induced fluorescence images are presented. The OH-PLIF images show instantaneous structures of turbulence in two combustor configurations at different fuel-equivalence ratios. Proper orthogonal decomposition and autocorrelations are performed on the OH-PLIF data to extract quantitative information about turbulent fluctuations and length-scale correlations. Changes in correlation length scales, representative of the integral length scales of the flow, and turbulent energy flow patterns are observed as a function of position in the combustor and fuel-equivalence ratio. Correlation length scales were found to increase with streamwise distance for all configurations. Dual-mode operation with supersonic and subsonic combustion is demonstrated in the facility. Correlation length scales and the growth rate of these length scales were found to be smaller in the subsonic combustion mode.