Flame stretch measurements during the interaction of premixed flames and Kármán vortex streets using PIV

Flame stretch measurements in a premixed, lean methane-air, V-flame interacting with a Kármán vortex street have been made using a particle image velocimeter. The flame curvature and strain rate along the flame have been measured over the range of -2.0-1.0 mm^-1 and -175-175 s^-1, respectively, which corresponds to a range of flame stretch from -475-200 s^-1. Results indicate that the curvature and strain rate are statistically independent. Flame stretch statistics based on individual flames are also considered since each flame represents a particular phase within the regular and periodic interaction cycle studied. These results indicate that for a particular flame the average stretch rate becomes independent of the average flame strain rate. A comparison among PIV measurements, OH planar laser-induced fluorescence (OH-PLIF) measurements, and numerical simulation reveals similar flame stretch statistics. Qualitative measurements concerning flame shape and the relative location of vortices within the reactant flow are also discussed.