Extended Proper Orthogonal Decomposition for Analysis of Unsteady Flames

The aim of this work is to present the use of proper orthogonal decomposition (POD) and extended proper orthogonal decomposition (EPOD) for revealing flame dynamics as a set of statistical quantities referred as modes. The flame fluctuations are used to derive an empirical functions base representing the most important features of the flame. The capabilities of the technique are exemplified in the case of an unsteady laminar flame. The flame is naturally unsteady and can be excited to amplify the fluctuations. The data base consists of synchronous Particle Image Velocimetry (PIV) and OH-Planar Laser Induced Fluorescence (OH-PLIF) measurements. It was found that the POD based upon the PIV vectors only reveals flow features when the excitation is added. On contrary, the OH-PLIF based POD performs well in any case and constitutes a suitable base for the EPOD analysis.