Vortex interactions with flames play a key role in many practical combustion applications. Such interactions form the basis for understanding naturally flickering buoyancy-dominated diffusion flames. These flames exhibit natural flicker as a result of a buoyancy-induced flow instability, which leads to the formation of strong vortical motions that subsequently interact with the combusting regions of the flame.
Under normal gravity conditions, the flames have a well-defined oscillation frequency which is inversely proportional to the square root of the burner diameter, D, and to a good approximation can be written as f » 1.5/D½, with D given in meters. A better understanding of flickering flame behavior promises to improve the current understanding of turbulent combustion systems, since a much wider range of local conditions is available to characterize the flame-flow interactions that are more dominant in turbulent flames.