Mechanism of flame evolution along a fine vortex

Abstract

Flame evolution along an unstretched, fine, straight vortex was numerically simulated when a perpendicular pre-mixed flame interacted with the vortex. The flame developed along the vortex by producing a precursor azimuthal vortex, which accelerated the flame along the straight vortex. Higher density ratios increased the propagation speed and the peak of the azimuthal vorticity attached to the flame tip. At lower density ratios propagation speed was smaller and the peak azimuthal vortices separated from the flame tip. A baroclinic effect produced the azimuthal vortex on the flame during the initial stage of propagation, but convection and stretch effects produced another azimuthal vortex in front of the flame during the later stages. The propagation speed of the flame during later stages was generally proportional to the maximum circumferential velocity of the vortex tube, but the proportionality factor was also a positive function of the density ratio and the Reynolds number of the vortex.