Nonlinear dynamics of upward propagating flames.

We study the influence of gravity on the dynamics of upward propagating premixed flames. We show that the role of gravity on the dispersion relation is small, but that the nonlinear effects are large. Using a Michelson Sivashinsky equation modified with a gravity term, it can be observed that the nonlinear dynamics of the crests is greatly influenced by gravity, as well as the final amplitude of the flame. A simple model is proposed to explain the role of gravity on the amplitude.

Nonlinear dynamics of flame fronts with large-scale stabilizing effects.

We investigate the influence of gravity and heat loss on the long-time nonlinear dynamics of premixed flames. We show that even when their influence remains weak in the linear regime they can significantly modify the long-time behavior. We suggest that the presence of such a large-scale stabilizing effect could be responsible for the creation of new cells on the front and the appearance of the strong persistent patterns observed in several recent experimental and numerical studies. It could also explain some statistical anomalies observed in the topology of flame fronts.

Complex network analysis of the gravity effect on premixed flames propagating in a Hele-Shaw cell.

We study the effect of gravity on spatiotemporal flame front dynamics in a Hele-Shaw cell from the viewpoint of complex networks. The randomness in flame front dynamics significantly increases with the gravitational level when the normalized Rayleigh number R_{a} is negative. This is clearly identified by two network entropies: the flame front network entropy and the transition network entropy. The irregular formation of large-scale wrinkles driven by the Rayleigh-Taylor instability plays an important role in the formation of high-dimensional deterministic chaos at R_{a}<0, resulting in the increase in the randomness of flame front dynamics.

Complex network analysis of spatiotemporal dynamics of premixed flame in a Hele-Shaw cell: A transition from chaos to stochastic state.

We study the dynamical state of a noisy nonlinear evolution equation describing flame front dynamics in a Hele-Shaw cell from the viewpoint of complex networks. The high-dimensional chaos of flame front fluctuations at a negative Rayleigh number retains the deterministic nature for sufficiently small additive noise levels. As the strength of the additive noise increases, the flame front fluctuations begin to coexist with stochastic effects, leading to a fully stochastic state. The additive noise significantly promotes the irregular appearance of the merge and divide of small-scale wrinkles of the flame front at a negative Rayleigh number, resulting in the transition of high-dimensional chaos to a fully stochastic state.