Coupling between fluid dynamics and combustion in a laminar vortex ring

Flame-vortex interactions are critical to the understanding of turbulent reacting flows. The impact of exothermicity on reacting vortex rings is investigated both numerically and experimentally to assess the dominant effect of heat release. Experimental observations of ring trajectories show an initial increase in ring speed in the early stage, followed by a large reduction in speed. It is found numerically that dilatation due to combustion heatrelease is the dominant effect over enhanced diffusivities in a reacting vortex ring. Increasing fuel volume in the ring beyond a critical limit, obtained from a simple model, actually decreases the amount of heatrelease during the early stage of the interaction. In addition, the increase in ring circulation led to a decrease in ring speed in the early stage of formation. Nitrogen dilution of the propane fuel reduces the flame luminosity and burnout time, as well as changes in details of the formation and dissipation of the luminous cap, with little change in the primary structure or dynamics of the interaction. The numerical simulations were successful in explaining most of the experimental observations, however, differences in flame structure and ring dynamics attributed to radiative heat loss were inconclusive when radiative heat loss was modeled as an overall decrease in flame temperature.