Flickering mode transition of dual pool flames

The anti-phase and in-phase flickering modes of dual pool flames were investigated numerically. Understanding that the deformation, stretch, and pinch-off of a buoyancy-driven flickering flame result from the formation and evolution of toroidal vortices, we analyzed the anti-phase and in-phase flickering modes from the perspective of vortex dynamics. The interaction between the inner-side shear layers of the two flames, which resembles that in the wake of a bluff body, was identified to be the key mechanism in determining the different flickering modes and verified qualitatively by the simulation results. Furthermore, the transition from the anti-phase to the in-phase mode can be understood as the outcome of strong viscous effect on vorticity diffusion between the inner-side shear layers, which is characterized by a special Reynolds number defined based on the gap flow between the two flames. This Reynolds number criterion for the transition between the two flickering modes has been demonstrated to agree with data from both the current simulation and the previous experiment.