A vortex-dynamical scaling theory for flickering buoyant diffusion flames. (24th September 2018)

• Record Type: Journal Article
• Authors: Xia, Xi; Zhang, Peng
• Is Part Of: Journal of fluid mechanics. Volume 855(2018)
• Page Start: 1156
• Page End: 1169
• Publication Date: 2018-09-24
• Subjects: flames, -- instability, -- vortex flows; Fluid mechanics -- Periodicals; 532.005
• DOI: 10.1017/jfm.2018.707
• Languages: English
• ISSNs: 0022-1120

Abstract

Abstract : The flickering of buoyant diffusion flames is associated with the periodic shedding of toroidal vortices that are formed under gravity-induced shearing at the flame surface. Numerous experimental investigations have confirmed the scaling, $f\propto D^{-1/2}$, where $f$ is the flickering frequency and $D$ is the diameter of the fuel inlet. However, the connection between the toroidal vortex dynamics and the scaling has not been clearly understood. By incorporating the finding of Gharib et al. ( J. Fluid Mech., vol. 360, 1998, pp. 121–140) that the detachment of a continuously growing vortex ring is inevitable and can be dictated by a universal constant that is essentially a non-dimensional circulation of the vortex, we theoretically established the connection between the periodicity of the toroidal vortices and the flickering of a buoyant diffusion flame with small Froude number. The scaling theory for flickering frequency was validated by the existing experimental data of pool flames and jet diffusion flames.