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Non-premixed jet flames represent a generic flame configuration with high relevance in many
combustion devices. The present work computationally investigates the case of a strongly
buoyant
non-premixed turbulent jet flame using Direct Numerical Simulation
(DNS). The simulation results unveil a weak upstream effect of the flame
on the non-burning region ahead of the flame base. A comparatively more
substantial effect of the flame is seen in the largescale motion, which
evolves under the influence of the periodic formation, growth, and
departure of large bulb-shaped low-density structures at the flame base,
as it is also seen in experiments. The analysis of the dominant
stability mechanism of the flame base essentially supports the
established concept of edge-flame propagation. Moreover, the
buoyancy-driven large-scale flow structures temporally generate a
further highly critical scenario, where large circumferential sections
of the flame base recede deeply downstream, which is shown to be
triggered by high local values of the scalar dissipation rate. With this
particular scenario the present work does not only bring to light an
important stabilization mechanism governed by large three-dimensional
structures, it also recalls the relevance of the scalar dissipation
rate, whose effect is often discarded in the commonly accepted theories
on flame stabilization.