Spiral dynamics of pulsating methane-oxygen flames on a circular burner

A premixed flame stabilized on a circular porous plug burner produces a uniform, steady luminous flame front. Throughout much of the parameter range hydrocarbon-oxygen mixtures form spiral-shaped fronts. In methane-oxygen flames at low pressure, the flame exhibits a sequence of states as a control parameter is decreased. These states include periodic rotation of a spiral front; precession of the spiral front in a direction opposite to its rotation, corresponding to doubly periodic petals-out meandering; and nonperiodic states with intermittent jumps associated with linear excursions of the tip, which occur after the spiral front has reached the boundary of the circular burner. We use Karhunen-Loeve (KL) analysis to find the coefficients of the dominant KL spatial eigenfunctions. Their phase space portraits and power spectra provide a description of the dynamics as flow rates are reduced and the system destabilizes. We discuss how these experimental results relate to previous theoretical studies that assume Euclidean symmetry for the experimental configuration.