Two-dimensional simulation in transitional jet diffusion flame with/without a duct

The numerical study was performed to examine the dynamic structure of metha ne and air jet diffusion flame with and without a duct in the transitional flow regime, that is, Re = 1000-2000. The flame sheet model of infinite che mical reaction and unit Lewis number were assumed in the simulation. The te mperature dependence of the viscosity and diffusivity of mixed gases was al so considered. The mechanism of vortex growth was explained by using the st reaklines visualized with marker particles, and the interrelation between v ortical and thermal structures is clarified for two cases with and without a duct. The presence of a duct leads to suppression of vortex growth in the stream wise direction of the methane jet, and therefore the flame spreadin g is significantly reduced. Furthermore, oscillatory shear stress and heat flux are discussed to understand vortex-flame interactions. It is found tha t in the transitional flow regime, there are similarities between oscillato ry momentum and heat transport inside the flame in both cases.