Vortex interaction in triple flickering buoyant diffusion flames

Abstract

Triple flickering buoyant diffusion flames of methane gas in equilateral triangle arrangement, as a nonlinear dynamical system of coupled oscillators, were computationally investigated. The four distinct dynamical modes (in-phase, death, rotation, and partially in-phase), that were originally observed in candle-flame experiments, were computationally reproduced for the first time. The four modes were interpreted from the perspective of vortex interaction and particularly of vorticity reconnection and vortex-induced flow. Specifically, the in-phase mode is caused by the periodic shedding of the trefoil vortex formed by the reconnection of three toroidal vortices; the death mode is due to the suppression of vortex shedding at small Reynolds numbers; the rotation mode appears as three toroidal vortices alternatively shed off with a constant phase difference; the partially in-phase model is caused by the vorticity reconnection of two toroidal vortices leaving another one shedding off in anti-phase. This work well establishes a bridge between the vortex dynamics and the nonlinear dynamics of the triple-flame system, which is believed to play a key role in understanding larger dynamical systems of multiple flickering flames.