DMD analysis for velocity fields of a laminar premixed flame with external acoustic excitation

The velocity fields of the laminar premixed flames with external acoustic excitation are studied in this work. The velocity fields in both burnt and unburnt regions have been experimentally investigated by PIV methodology. Different acoustic modulations have been applied to the flames. Dynamical mode decomposition (DMD) is adopted to elaborate the interaction mechanisms between flames and acoustics. Experimental results indicate that both the flame shapes and the velocity fields adapt to acoustic modulations. The wrinkled flame produces hydrodynamic disturbances in the nearby flow. Two different propagating motions including convective mode and mixed mode are presented in the axial component of velocity fields, and the motions are related to the Strouhal number (St). Meanwhile, the motions of transverse flow are tightly coupled with the wrinkled flame fronts. The wrinkled flame takes a role in the vortex behavior in the vicinity of the reaction layer, and the vorticity sources in both perturbed and unperturbed flames are distinguished. In addition, the flickering mode is observed and extracted in the work. This study presents some significance with respect to how forcing studies on elementary flames interpret their observations.