EXPERIMENTAL-EVIDENCE OF SELF-EXCITED RELAXATION OSCILLATIONS LEADING TO HOMOCLINIC BEHAVIOR IN SPREADING FLAMES

Flame spreading over liquid alcohols has been experimentally characterized by three methods: temperature measurements along the liquid surface, schlieren pictures of the temperature gradients induced in the liquid by Marangoni flows, and direct video recording of the flame spreading. Three distinct spreading regimes have been observed: a fast and a slow propagation regime of uniform spreading at high and low values of the initial fuel surface temperature, and an oscillatory propagation regime at intermediate temperatures. The oscillations start as a Hopf bifurcation from the fast propagation steady state. Moreover, the collision of the limit cycle with the slow spreading branch originates a homoclinic connection revealed by a logarithmic divergence in the oscillation period, a main feature of generic homoclinic points.