Simulation of vortical structures in a jet diffusion flame

Abstract

The dynamics of a transitional propane jet diffusion flame with a fuel‐jet velocity of 2.2 m/s has been studied using an implicit, third‐order‐accurate, upwind numerical scheme. The large‐scale vortices outside the flame surface and the small‐scale ones inside were simulated simultaneously, and their interactions with the flame surface were investigated. Numerical experiments were conducted to gain insight into the influence of buoyancy and shear‐layer forcing on the development of the outer and inner vortices. In the presence of buoyancy forces, the outer vortices developed as part of the solution, and the vortex‐crossing frequency was approximately 15 Hz. The inner structures were manifested from a weak perturbation the vorticity that was introduced at the nozzle exit, and, at 185 Hz, these vortices were found to travel farther downstream. It was also found that the inner vortices do not play a role in the formation of the outer vortices, and vice versa. However, the growth of the inner vortices in the downstream locations is strongly influenced by the slowly moving outer vortices.